Abstract:
An ECU executes a program including the steps of: calculating a base timing of injection (INJB); determining whether an engine knocks; if the engine knocks, increasing a correction value INJK(I) applied to correct a timing of injection; and calculating the base timing of injection INJB plus the correction value INJK(I) to obtain a timing of injection INJ.

Description:
[0001]     This nonprovisional application is based on Japanese Patent Application No. 2004-377397 filed with the Japan Patent Office on Dec. 27, 2004, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to control devices for internal combustion engines and particularly to control devices for internal combustion engines having a cylinder receiving fuel directly injected thereinto.  
         [0004]     2. Description of the Background Art  
         [0005]     Conventionally a direct injection engine directly injecting fuel into a cylinder is commercially available. The direct injection engine includes an engine allowing fuel to be injected at an intake stroke to combust a homogenous air fuel mixture to provide homogenous combustion, and an engine allowing fuel to be injected at a compression stroke to combust an air fuel mixture with an air fuel ratio increased around an ignition plug to provide stratified combustion. Furthermore, there also exists a direct injection engine dividing fuel injection in two, i.e., injecting the fuel at intake and compression strokes. Such a direct injection engine can also knocks, and such knocking needs to be minimized.  
         [0006]     Japanese Patent Laying-Open No. 2004-003429 discloses a controller that can reduce knocking caused in a stratified combustion mode of operation, without inviting misfire, poor exhaust emission and the like. As described in the publication, in the stratified combustion mode of operation when a knock detector detects that engine knocks the controller controls a knock prevention controller for the stratified combustion mode to introduce spark retard for correction as well as fuel injection retard for correction and switches the stratified combustion mode to a homogenous combustion mode. In reducing the knocking, as controlled, when an amount or result of correcting at least one of spark retard and fuel injection retard exceeds a prescribed threshold value, the stratified combustion mode is switched to a double injection stratified combustion mode. When the detector detects that the engine operating in the double injection stratified combustion mode knocks, a knock prevention controller associated with the mode corrects at least one of a ratio between fuel injected at the intake stroke and that injected at the compression stroke, the timing of fuel injection at the intake stroke, and the timing of spark. It should be noted that the timing of fuel injection at the compression stroke is not corrected. Furthermore in the double injection stratified combustion mode if the engine knocks and the knocking is reduced as controlled, and as a result at least one of an amount or result of correcting the fuel distribution ratio, the timing of fuel injection at the intake stroke, and the timing of spark exceeds a prescribed threshold value, then the double injection stratified combustion mode is switched to a homogenous combustion mode.  
         [0007]     As disclosed in the publication, the knock reduction controller can introduce a spark retard in the stratified combustion mode of operation for correction to prevent knocking, while introducing a fuel injection retard for correction corresponding to the amount of the spark retard for correction so that in the stratified combustion mode of operation, fuel injection and spark can be timed to have a relationship allowing a spark to be provided when injected fuel flows in a vicinity of a spark plug. Thus in the stratified combustion mode of operation a spark retard for correction can be introduced to prevent an engine from knocking while misfire, poor exhaust emission, and the like can be prevented by introducing a fuel injection retard for correction.  
         [0008]     Furthermore, in general, the double injection stratified combustion mode allows spark and fuel injection to be timed for correction over a wider range than the stratified combustion mode. Thus in the former mode knocking can be more readily reduced than in the latter mode. As such, in the stratified combustion mode of operation when an amount or result of correction introduced to prevent the engine from knocking exceeds a prescribed threshold value (e.g., the amount or result is limited by a correction guard value), then a decision is made that the knocking cannot completely be prevented in the stratified combustion mode, and the stratified combustion mode is switched to the double injection stratified combustion mode. Such knocking that cannot completely be prevented in the stratified combustion mode, can thus be handled.  
         [0009]     Furthermore, in the double injection stratified combustion mode, in addition to a timing of spark a fuel distribution ratio (an amount of fuel injected at the intake stroke) and a timing of injection of fuel at the intake stroke can also be corrected to prevent an engine from knocking. Note that if the fuel distribution ratio (the amount of fuel injected at the intake stroke) is corrected, the amount can be reduced to a level disallowing self-ignition to prevent the engine from knocking, or, in contrast, the amount can be increased and heat generated as injected fuel vaporizes at the intake stroke can be utilized to reduce the temperature of a gas present in the cylinder to prevent the engine from knocking.  
         [0010]     Furthermore the homogenous combustion mode allows spark and fuel injection to be timed for correction over a further wider range than the stratified combustion mode and the double injection stratified combustion mode. Thus in the former mode knocking can be further more readily reduced than in the latter modes. As such, in the stratified combustion mode of operation if the detector detects that the engine knocks or in the double injection stratified combustion mode of operation if the engine knocks and the knocking is reduced as controlled, and as a result at least one of an amount or result of correcting the fuel distribution ratio, the timing of fuel injection at the intake stroke, and the timing of spark exceeds a prescribed threshold value, then the mode is switched to the homogenous combustion mode. Such knocking that cannot completely be prevented in the double injection stratified combustion mode or (the stratified combustion mode), can thus be handled.  
         [0011]     As disclosed in Japanese Patent Laying-Open No. 2004-003429, the knocking prevention controller corrects a timing of fuel injection as it exerts control to prevent knocking. It should be noted, however, that an in-cylinder air fuel mixture has a distribution (in concentration) that can vary with the timing of fuel injection. The air fuel mixture having a varied distribution results in a varied timing (or speed) of propagation of flame in the cylinder. The timing of propagation of flame in the cylinder that varies with location can cause the engine to knock. The publication, however, neither discloses nor suggests such a disadvantage in connection with the knock prevention controller disclosed therein. Thus there still exists the problem of the uncorrected timing of propagation of flame in a cylinder.  
       SUMMARY OF THE INVENTION  
       [0012]     An object of the present invention is to provide an appropriate timing of propagation of a flame in a cylinder to prevent an engine from knocking.  
         [0013]     Another object of the present invention is to reduce smoke, insufficient vaporization of fuel, and insufficient mixture of fuel and air.  
         [0014]     The present invention in one aspect provides a control device for an internal combustion engine including an injector injecting fuel directly into a cylinder. The control device includes: a detector detecting that an engine knocks; and a controller controlling the injector to provide a faster timing of propagation of flame in the cylinder toward an intake side when that the engine knocks is detected.  
         [0015]     In a direct injection engine injecting fuel into a cylinder from an intake side the timing of propagation of flame toward the intake side is slower than the timing of propagation of flame toward the exhaust side because of the different flame propagation distances caused by spark plug offset mount, and the combustion chamber wall temperature distribution. As such, the intake side&#39;s air fuel mixture is adiabatically compressed. As a result, the engine tends to knock. The present invention prevents the engine from knocking at the intake side by advancing the timing of propagation of flame in the cylinder toward the intake side when that the engine knocks is detected. The cylinder can thus have a flame propagated therein timely to prevent the intake side from having an air fuel mixture adiabatically compressed resulting in the engine knocking.  
         [0016]     Preferably the controller controls the injector to increase an air fuel ratio in the cylinder at the intake side to provide a faster timing of propagation of flame in the cylinder toward the intake side.  
         [0017]     In accordance with the present invention, for conditions such as full load, an air fuel ratio controlled to be richer than a theoretical air fuel ratio, and other similar conditions for which knocking is a problem, an air fuel ratio richer (or lower) than the cylinder&#39;s internal, overall air fuel ratio tends to result in a slower timing of propagation of flame. The present invention can render the intake side&#39;s air fuel ratio lean (or high), i.e., control it to be close to the theoretical air fuel ratio to provide an advanced timing of propagation of flame toward the intake side.  
         [0018]     Still preferably the controller introduces a fuel injection advance at an intake stroke.  
         [0019]     In accordance with the present invention when a fuel injection advance is introduced at an intake stroke, in the cylinder the piston&#39;s top portion is impinged on by fuel so that a large portion of the fuel is carried through the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel mixture can be controlled to be lean, i.e., close to the theoretical air fuel ratio.  
         [0020]     Still preferably the control device further includes a limiter limiting a timing of injection of fuel to be no earlier than a first predetermined timing of injection and no later than a second predetermined timing of injection.  
         [0021]     The present invention can prevent fuel injection advanced and retarded more than required. This can prevent the piston&#39;s top portion from having fuel adhering thereon more than required resulting in smoking, the fuel insufficiently evaporating, and the fuel and air being mixed insufficiently.  
         [0022]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the timing of injection is the first timing.  
         [0023]     In accordance with the present invention if fuel is injected as timed as controlled and the engine still knocks, a spark retard can be introduced to prevent the engine from knocking.  
         [0024]     Still preferably the cylinder receives fuel divided and thus injected twice at intake and compression strokes and the controller introduces a fuel injection retard at the compression stroke.  
         [0025]     In accordance with the present invention when a fuel injection retard is introduced at a compression stroke, in the cylinder the piston&#39;s top portion is impinged on by fuel so that a large portion of the fuel is carried through the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel mixture can be controlled to be lean, i.e., close to the theoretical air fuel ratio.  
         [0026]     Still preferably the control device further includes a limiter limiting a timing of injection of fuel to be no earlier than a first predetermined timing of injection and no later than a second predetermined timing of injection.  
         [0027]     The present invention can prevent fuel injection advanced and retarded more than required. This can prevent the piston&#39;s top portion from having fuel adhering thereon more than required resulting in smoking, the fuel insufficiently evaporating, and the fuel and air being mixed insufficiently.  
         [0028]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the timing of injection is the second timing.  
         [0029]     In accordance with the present invention if fuel is injected as timed as controlled and the engine still knocks, a spark retard can be introduced to prevent the engine from knocking.  
         [0030]     Still preferably the controller introduces the fuel injection retard at the compression stroke and in addition thereto increases an amount of fuel injected at the compression stroke.  
         [0031]     In accordance with the present invention when fuel is injected at a compression stroke in an increased amount the fuel impinges in the cylinder on the piston&#39;s top portion so that an increased amount of the fuel is carried in the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel ratio can be controlled to be lean or close to a theoretical air fuel ratio.  
         [0032]     Still preferably the control device further includes a limiter limiting the amount to be at least a first predetermined amount and at most a second predetermined amount.  
         [0033]     The present invention can prevent fuel from being injected in an amount more and less than required. An appropriate air fuel ratio can be obtained.  
         [0034]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the amount is the second amount.  
         [0035]     In accordance with the present invention if fuel is injected in an amount as controlled and the engine still knocks then a spark retard can be introduced to prevent the engine from knocking.  
         [0036]     The present invention in another aspect provides a control device for an internal combustion engine including an injector injecting fuel directly into a cylinder. The control device includes: a detector detecting a timing of propagation of flame in the cylinder; and a controller controlling the injector to advance a timing of propagation of flame in the cylinder toward an intake side when the timing of propagation of flame in the cylinder toward the intake side is slower than that of propagation of flame in the cylinder toward an exhaust side.  
         [0037]     In a direction injection engine injecting a fuel into a cylinder from an intake side the timing of propagation of flame toward the intake side is slower. If the timing of propagation of flame toward the intake side is slower than that of propagation of flame toward the exhaust side, the intake side&#39;s air fuel mixture is adiabatically compressed, and the engine can knock. To prevent this, the present invention provides a faster timing of propagation of the flame in the cylinder toward the intake side. Thus the flame can be propagated in the cylinder timely. This can prevent the intake side from having an air fuel mixture adiabatically compressed resulting in the engine knocking. Thus the cylinder can have a flame therein propagated timely to prevent the engine from knocking.  
         [0038]     Preferably the controller controls the injector to increase an air fuel ratio in the cylinder at the intake side to provide a faster timing of propagation of flame in the cylinder toward the intake side.  
         [0039]     In accordance with the present invention, for conditions such as full load, an air fuel ratio controlled to be richer than a theoretical air fuel ratio, and other similar conditions for which knocking is a problem, an air fuel ratio richer (or lower) than the cylinder&#39;s internal, overall air fuel ratio tends to result in a slower timing of propagation of flame. The present invention can render the intake side&#39;s air fuel ratio lean (or high), i.e., control it to be close to the theoretical air fuel ratio to provide an advanced timing of propagation of flame toward the intake side.  
         [0040]     Still preferably the controller introduces a fuel injection advance at an intake stroke.  
         [0041]     In accordance with the present invention when a fuel injection advance is introduced at an intake stroke, in the cylinder the piston&#39;s top portion is impinged on by fuel so that a large portion of the fuel is carried through the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel mixture can be controlled to be lean, i.e., close to the theoretical air fuel ratio.  
         [0042]     Still preferably the control device further includes a limiter limiting a timing of injection of fuel to be no earlier than a first predetermined timing of injection and no later than a second predetermined timing of injection.  
         [0043]     The present invention can prevent fuel injection advanced and retarded more than required. This can prevent the piston&#39;s top portion from having fuel adhering thereon more than required resulting in smoking, the fuel insufficiently evaporating, and the fuel and air being-mixed-insufficiently.  
         [0044]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the timing of injection is the first timing.  
         [0045]     In accordance with the present invention if fuel is injected as timed as controlled and the engine still knocks, a spark retard can be introduced to prevent the engine from knocking.  
         [0046]     Still preferably the cylinder receives fuel divided and thus injected twice at intake and compression strokes and the controller introduces a fuel injection retard at the compression stroke.  
         [0047]     In accordance with the present invention when a fuel injection retard is introduced at a compression stroke, in the cylinder the piston&#39;s top portion is impinged on by fuel so that a large portion of the fuel is carried through the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel mixture can be controlled to be lean, i.e., close to the theoretical air fuel ratio.  
         [0048]     Still preferably the control device further includes a limiter limiting a timing of injection of fuel to be no earlier than a first predetermined timing of injection and no later than a second predetermined timing of injection.  
         [0049]     The present invention can prevent fuel injection advanced and retarded more than required. This can prevent the piston&#39;s top portion from having fuel adhering thereon more than required resulting in smoking, the fuel insufficiently evaporating, and the fuel and air being mixed insufficiently.  
         [0050]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the timing of injection is the second timing.  
         [0051]     In accordance with the present invention if fuel is injected as timed as controlled and the engine still knocks, a spark retard can be introduced to prevent the engine from knocking.  
         [0052]     Still preferably the controller introduces the fuel injection retard at the compression stroke and in addition thereto increases an amount of fuel injected at the compression stroke.  
         [0053]     In accordance with the present invention when fuel is injected at a compression stroke in an increased amount the fuel impinges in the cylinder on the piston&#39;s top portion so that an increased amount of the fuel is carried in the cylinder toward the exhaust side. Thus the intake side&#39;s air fuel ratio can be controlled to be lean or close to a theoretical air fuel ratio.  
         [0054]     Still preferably the control device further includes a limiter limiting the amount to be at least a first predetermined amount and at most a second predetermined amount.  
         [0055]     The present invention can prevent fuel from being injected in an amount more and less than required. An appropriate air fuel ratio can be obtained.  
         [0056]     Still preferably the control device further includes a spark retarder introducing a spark retard when that the engine knocks is detected and the amount is the second amount.  
         [0057]     In accordance with the present invention if fuel is injected in an amount as controlled and the engine still knocks then a spark retard can be introduced to prevent the engine from knocking.  
         [0058]     Still preferably, more than one detector is provided in the cylinder.  
         [0059]     In accordance with the present invention a timing of propagation of flame can be detected in the cylinder at a plurality of locations with high precision.  
         [0060]     Still preferably the detector is disposed in the cylinder at two locations closer to the intake and exhaust sides, respectively.  
         [0061]     A timing of propagation of flame toward the intake side and that of propagation of flame toward the exhaust side can be detected.  
         [0062]     Still preferably the detector is an ion current detection device.  
         [0063]     Internal to a flame an air fuel mixture has its molecules ionized. As such, the flame is electrically conductive. In accordance with the present invention an ion current detection device can be provided to detect whether a current flows to detect a timing of propagation of flame.  
         [0064]     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0065]      FIG. 1  schematically shows a configuration of an engine of a vehicle mounting the present control device in a first embodiment.  
         [0066]      FIG. 2  is a flow chart of a program for control executed by an ECU implementing the present control device of the first embodiment.  
         [0067]      FIG. 3  is a first view showing fuel injected at an intake stroke.  
         [0068]      FIG. 4  is a first view showing an air fuel mixture&#39;s condition at ignition.  
         [0069]      FIG. 5  is a second view showing fuel injected at an intake stroke.  
         [0070]      FIG. 6  is a second view showing an air fuel mixture&#39;s condition at ignition.  
         [0071]      FIG. 7  schematically shows a configuration of an engine of a vehicle mounting the present control device in a second embodiment.  
         [0072]      FIG. 8  is a flow chart of a program for control executed by an ECU implementing the present control device of the second embodiment.  
         [0073]      FIG. 9  is a flow chart of a program for control executed by an ECU implementing the present control device of the third embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0074]     Hereinafter with reference to the drawings the present invention in embodiments will be described. In the following description, identical components are identically denoted and also identical in name and function.  
       First Embodiment  
       [0075]     With reference to  FIG. 1  will be described an engine of a vehicle mounting the present control device in a first embodiment. In the present embodiment the control device is implemented for example by a program executed by an electronic control unit (ECU)  200  shown in  FIG. 1 .  
         [0076]     Engine  100  intakes air from an air cleaner  102  in an amount as adjusted by a throttle valve  104  which is a motor driven, electric machinery controlled-throttle valve.  
         [0077]     The air is introduced into a cylinder  106  (a combustion chamber) and mixed with fuel therein. Cylinder  106  receives fuel directly injected thereinto from an injector  108 . More specifically, injector  108  has an injection nozzle hole located in cylinder  106 . The fuel is injected from that side of cylinder  106  which intakes (or introduces) air.  
         [0078]     The fuel is injected at an intake stroke, although the timing of injection of the fuel is not limited to the intake stroke. Furthermore, while in the present embodiment engine  100  is described as a direct injection engine with injector  108  having its injection nozzle hole located in cylinder  106 , in addition to injector  108  for direct injection an injector for port injection may also be introduced.  
         [0079]     The air fuel mixture in cylinder  106  is ignited by a spark plug  110  and thus combusts. The combusted air fuel mixture, or exhaust gas, is purified by a ternary catalyst  112  and then exhausted external to the vehicle. As the air fuel mixture combusts, a piston  114  is pushed downward and a crankshaft  116  rotates.  
         [0080]     Cylinder  106  has a top portion provided with an intake valve  118  and an exhaust valve  120 . Cylinder  106  introduces air in an amount and as timed, as controlled by intake valve  118 , and exhausts gas in an amount and as timed, as controlled by exhaust valve  120 . Intake valve  118  is driven by a cam  122  and exhaust valve  120  is driven by a cam  124 .  
         [0081]     ECU  200  controls a timing of ignition, a timing of fuel injection, an amount of fuel injected, a timing of opening and closing the intake and exhaust valves, and the like to operate engine  100 , as desired. ECU  200  receives a signal representative of the cam&#39;s position from a cam angle sensor  300 , a signal representative of a rate of rotation of crank shaft  116  (or the engine) and an angle of rotation of crank shaft  116  from a crank angle sensor  302 , and a signal representative of vibration in intensity of engine  100  from a knock sensor  304 .  
         [0082]     ECU  200  employs the signals received from the sensors and a map and a program stored in a memory (not shown) to control engine  100 . In the present embodiment ECU  200  receives a signal transmitted from knock sensor  304  and therefrom detects whether the engine knocks, and if ECU  200  detects that the engine knocks ECU  200  corrects a timing of injection of the fuel.  
         [0083]     With reference to  FIG. 2 , ECU  200  implementing the control device in the present embodiment executes a program for control structured as described hereinafter.  
         [0084]     At step (S)  100 , ECU  200  calculates a timing of base injection of the fuel INJB as based on a map with the engine&#39;s rate of rotation, load (torque) and the like serving as parameters. Timing INJB is calculated so that the fuel is injected at an intake stroke (e.g., before top dead center (BTDC): 90° to 180°). Furthermore, timing INJB is calculated to be larger for faster timing of injection. How timing INJB is calculated will not specifically be described herein as it can be calculated by well-known, general technique.  
         [0085]     At S 102  ECU  200  determines from a signal transmitted from knock sensor  304  whether the engine knocks. Whether the engine knocks or not can be determined by well-known, general technique. When the engine knocks (YES at S 102 ), the process proceeds with S 104 . Otherwise (NO at S 102 ), the process proceeds with S 106 .  
         [0086]     At S 104  ECU  200  calculates a correction value applied to correct the timing of injection INJK(I)=INJK(I−1)+A, wherein INJK(I−1) represents a previously calculated, value for correction and A represents a positive constant. More specifically, at S 104  correction value INJK(I) is increased and an injection advance is introduced.  
         [0087]     At S 106  ECU  200  calculates correction value INJK(I)=INJK(I−1)−B, wherein B represents a positive constant. More specifically, at S 104  correction value INJK(I) is decreased and an injection retard is introduced. The process then proceeds with S 108 .  
         [0088]     At S 108  ECU  200  determines whether correction value INJK(I) is no more than a predetermined upper limit value INJK(X) set to have a value so that smoke generated by fuel adhering to the top portion of piston  114  has an amount falling within a tolerable range. Correction value INJK(I) is no more than upper limit value INJK(X) (YES at S 108 ) the process proceeds with S 110 . Otherwise (NO at S 108 ) the process proceeds with S 112 .  
         [0089]     At S 110  ECU  200  determines whether correction value INJK(I) is no less than a predetermined lower limit value INJK(Y) set to have a value allowing the fuel to appropriately evaporate and the fuel and air to be mixed together appropriately. If correction value INJK(I) is no more than lower limit value INJK(Y) (YES at S 110 ) then the process proceeds with S 116 . Otherwise (NO at S 110 ) the process proceeds with S 114 .  
         [0090]     At S 112  ECU  200  sets upper limit value INJK(X) at correction value INJK(I). Subsequently the process proceeds with S 116 . At S 114  ECU  200  sets lower limit value INJK(Y) at correction value INJK(I). Subsequently the process proceeds with S 116 .  
         [0091]     At S 116  ECU  200  calculates the timing of base injection INJB plus correction value INJK(I) to obtain a timing of injection INJ. At this timing of injection INJ injector  108  injects the fuel.  
         [0092]     In accordance with the configuration and flowchart as described above ECU  200  implementing the control device in the present embodiment operates, as will be described hereinafter.  
         [0093]     While engine  100  operates, the base timing of injection INJB is calculated (S 100 ) and from a signal transmitted from knock sensor  304  whether the engine knocks or not is determined (S 102 ).  
         [0094]     As shown in  FIG. 3 , if a timing of injection is set to be retarded (or closer to the bottom dead center), the fuel, sprayed and thus provided with force to penetrate, proceeds through cylinder  106  downward. In that case, as seen in  FIG. 3 , a clockwise stream (tumble) acts to push, and when a spark is made, cylinder  106  internally has an air fuel ratio relatively rich at a location closer to the intake side and relatively lean at a location closer to the exhaust side, as shown in  FIG. 4 .  
         [0095]     After the spark is made, the timing of propagation of a flame is significantly affected by the air fuel ratio (or an air fuel mixture&#39;s concentration), the temperature of a wall of cylinder  106 , and the like. In general, the timing of propagation of flame is fastest for theoretical air fuel ratio. Accordingly, an air fuel ratio richer or leaner than the theoretical air fuel ratio contributes to a faster timing of propagation of flame. Furthermore, the wall with lower temperature tends to contribute to slower timing of propagation of flame. Thus the timing of propagation of flame toward the intake side having an air fuel ratio richer than the theoretical air fuel ratio and closer to a wall lower in temperature, tends to be retarded. In that case, the air fuel mixture closer to the intake side is adiabatically compressed, and the engine tends to knock at the intake side.  
         [0096]     When the engine knocks (YES at S 102 ) a correction value INJK(I) is calculated as INJK(i)=INJK(I−1)+A to provide an increased amount for correction (S 104 ). If the calculated correction value INJK(I) is no more than upper limit value INJK(X) (YES at S 108 ) and also no less than lower limit value INJK(Y) (YES at S 110 ) then the base timing of injection INJB plus correction value INJK(I) is calculated to obtain a timing of injection NJ (Si  16 ). Thus, the timing of injection INJ is advanced.  
         [0097]     When the timing of injection INJ is advanced or an injection advance is introduced, the fuel injected from injector  108  impinges on the top portion of piston  114 , as shown in  FIG. 5 . Thus a large portion of the injected fuel is carried to the exhaust side. Thus, as shown in  FIG. 6 , when a spark is made the exhaust side has a relatively rich air fuel ratio and the intake side has a relatively lean air fuel ratio. In other words, the intake side has an air fuel ratio relatively lean to be close to the theoretical air fuel ratio. This can provide a faster timing of propagation of flame toward the intake side to prevent the engine from knocking at the intake side.  
         [0098]     If an injection advance more than required is introduced, however, the fuel adhering to the top portion of piston  114  may generate an increased amount of smoke. Accordingly, an upper limit is set for correction value INJK(I).  
         [0099]     More specifically, if a calculated correction value INJK(I) is no less than upper limit value INJK(X) (NO at S 108 ), upper limit value INJK(X) is set as correction value INJK(I). More specifically, correction value INJK(I) finally calculated is limited to be smaller than upper limit value INJK(X). This can reduce smoke exceeding a tolerable range.  
         [0100]     If the engine does not knock (NO at S 102 ), injection retard is introduced. More specifically, correction value INJK(I) is calculated as INJK(I−1)−B and thus reduced (S 106 ).  
         [0101]     If the calculated correction value INJK(I) is no more than upper limit INJK(X) (YES at S 108 ) and also no less than lower limit value INJK(Y) (YES at S 110 ), the base timing of injection INJB plus correction value INJK(I) is calculated to obtain a timing of injection INJ (S 116 ). Thus, timing of injection INJ is retarded.  
         [0102]     If injection retard more than required is introduced, however, insufficient vaporization of the fuel, insufficient mixture of the fuel and air, and the like may be invited. Accordingly, a lower limit is set for correction value INJK(I).  
         [0103]     More specifically, if a calculated correction value INJK(I) is no more than lower limit value INJK(Y) (NO at S 110 ), lower limit value INJK(Y) is set as correction value INJK(I). More specifically, correction value INJK(I) finally calculated is limited to be at least lower limit value INJK(Y). This can reduce insufficient vaporization of the fuel, insufficient mixture of the fuel and air, and the like.  
         [0104]     Thus when the ECU implementing the control device in accordance with the present embodiment detects that an engine knocks, the ECU introduces a fuel injection advance at an intake stroke to advance a timing of injection (or set the timing of injection closer to the top dead center). Thus in the cylinder the intake side has an air fuel ratio relatively lean to be close to a theoretical air fuel ratio to provide a faster timing of propagation of flame toward the intake side. This can contribute to reduced adiabatical compression of the air fuel mixture at the intake side and hence reduced knocking.  
       Second Embodiment  
       [0105]     With reference to  FIGS. 7 and 8  the present invention in a second embodiment will be described. In the first embodiment when that an engine knocks is detected a fuel injection advance is introduced at an intake stroke to reduce knocking. In the present embodiment when that an engine knocks is detected and in a cylinder a timing of propagation of flame toward an intake side is slower than that of propagation of flame toward an exhaust side a fuel injection advance is introduced at an intake stroke.  
         [0106]     A timing of propagation of flame in the cylinder is detected by an ion current detection device provided at the cylinder. The remainder is identical in arrangement to that described in the first embodiment and also identical in function.  
         [0107]     With reference to  FIG. 7 , an engine of a vehicle having mounted therein the present control device in accordance with the present embodiment, will be described. As shown in the figure, cylinder  106  has intake and exhaust sides with their respective wall surfaces provided with ion current detection devices  306  and  308 , respectively, although the devices are not limited in location to such two locations.  
         [0108]     In the flame, the air fuel mixture has molecules ionized. As such, the flame is electrically conductive. As such, when voltage is applied to electrode of ion current detection devices  306 ,  308  inserted into the air fuel mixture, a current flows.  
         [0109]     In the present embodiment ion current detection device  306 ,  308  detects a current flowing through electrode and a signal representing a resultant detection is input to ECU  200 . ECU  200  detects a timing of flowing the current as that of propagation of the flame.  
         [0110]     With reference to  FIG. 8 , ECU  200  implementing the control device in accordance with the present invention executes a program for control structured as will now be described hereinafter. Note that any step identical to that of the program described in the first embodiment is identically labeled.  
         [0111]     At S 200  ECU  200  detects from a signal received from ion current detection devices  306  and  308  a timing of propagation of flame in cylinder  106  toward the intake side TIN and a timing of propagation of flame in the cylinder toward the exhaust side TEX.  
         [0112]     At S 202  ECU  200  detects from a signal received from knock sensor  304  whether engine knocks. If so (YES at S 202 ) the process proceeds with S 204 . Otherwise (NO at S 202 ) the process proceeds with S 116 .  
         [0113]     At S 204  ECU  200  determines whether timing TIN is slower than timing TEX. If so (YES at S 204 ), the process proceeds with S 104 . Otherwise (NO at S 204 ) the process proceeds with S 106 .  
         [0114]     In accordance with the configuration and flow chart as described above, ECU  200  implementing the control device in accordance with the present invention operates as described hereinafter.  
         [0115]     While engine  100  operates, a base timing of injection INJB is calculated (S 100 ) and from signals received from ion current detection devices  306  and  308  timing TIN and timing TEX are detected (S 200 ). Furthermore from a signal received from knock sensor  304  whether the engine knocks or not is determined (S 202 ).  
         [0116]     If the engine knocks (YES at S 202 ) and timing TIN is slower than timing TEX (YES at  204 ), a different timing of propagation of flame is considered to cause the engine to knock.  
         [0117]     Accordingly, correction value INJK(I) is calculated as INJK(I−1)+A to provide an increased amount for correction (S 104 ) and finally, timing of injection INJ is advanced. A faster timing of propagation of flame toward the intake side can be achieved and the engine&#39;s knocking at the intake side can be reduced.  
         [0118]     If the engine knocks (YES at S 202 ) and timing TIN is faster than timing TEX (NO at S 204 ), then a factor other than timing of propagation of flame is considered to cause the engine to knock.  
         [0119]     In that case, correction value INJK(I) is calculated as INJK(I−1)−B and thus reduced (S 106 ) and finally, timing of injection INJ is retarded.  
         [0120]     Thus an ECU implementing the control device in accordance with the present embodiment introduces injection advance to set a timing of injection to be faster (or closer to the top dead center) when an engine knocks and the timing of propagation of flame toward an intake side TIN is slower than that of propagatin of flame toward an exhaust side TEX. This can also provide an effect similar to that achieved in the first embodiment.  
       Third Embodiment  
       [0121]     With reference to  FIG. 9  the present invention in a third embodiment will be described.  
         [0122]     In the first and second embodiments a timing of injection of fuel at an intake stroke is corrected to reduce knocking. In the present embodiment a timing of injection and in addition thereto that of spark are corrected. The remainder is identical in arrangement to the first or second embodiment and also identical in function.  
         [0123]     With reference to  FIG. 9 , ECU  200  implementing the control device in accordance with the present embodiment executes a program for control structured as described hereinafter. The ECU executes the program described in the first or second embodiment and in addition thereto a program as will be described hereinafter.  
         [0124]     At S 300  ECU  200  calculates a base timing of spark SAB as based on a map with the engine&#39;s rate of rotation, load (torque) and the like serving as parameters. Note that the base timing of spark SAB can be calculated by well-known, general techniques.  
         [0125]     At S 302  ECU  200  determines from a signal transmitted from knock sensor  304  whether the engine knocks. Whether the engine knocks or not can be determined by well-known, general technique. When the engine knocks (YES at S 102 ), the process proceeds with S 304 . Otherwise (NO at S 302 ), the process ends.  
         [0126]     At S 304  ECU  200  determines whether a correction value applied to correct a timing of injection INJK(I) is equal to upper limit value INJK(X). IF so, (YES at S 304 ) the process proceeds with S 306 . Otherwise (NO at S 304 ), the process proceeds with S 308 .  
         [0127]     At S 306  ECU  200  calculates a correction value applied to correct a timing of spark SAK(I) as SAK(I−1)−C, wherein SAK(I−1) represents a previously calculated correction value and C represents a positive constant. More specifically, at S 306 , correction value SAK(I) is reduced to introduce a spark retard.  
         [0128]     At S 308  ECU  200  calculates correction value SAK(I) as SAK(I−1)+D, wherein D represents a positive constant. More specifically at S 308  correction value SAK(I) is increased to introduce a spark advance.  
         [0129]     At S 310  ECU  200  determines whether correction value SAK(I) is no more than a predetermined upper limit value SAK(X) set to have a value allowing engine  100  to provide an output (or torque) falling within a tolerable range. If correction value SAK(I) is no more than upper limit value SAK(X) (YES at  310 ), the process proceeds with S 314 . Otherwise (NO at S 310 ) the process proceeds with S 312 .  
         [0130]     At S 312  ECU  200  sets upper limit value SAK(X) at correction value SAK(I). Subsequently the process proceeds with S 314 , at which step ECU  200  calculates the base timing of spark SAB plus correction value SAK(I) to provide a timing of spark SA, at which timing, cylinder  106  has its internal air fuel mixture ignited.  
         [0131]     In accordance with the configuration and flow chart as described above ECU  200  implementing the control device in accordance with the present embodiment operates, as will be described hereinafter.  
         [0132]     While engine  100  operates, the base timing of spark SAB is calculated (S 300 ) and from a signal transmitted from knock sensor  304  whether the engine knocks or not is determined (S 302 ).  
         [0133]     If the engine knocks (YES at  302 ), then a decision is made as to whether correction value INJK(I) is equal to upper limit value INJK(X) (S 304 ). Correction value INJK(I) equal to upper limit value INJK(X) (YES at S 304 ) is considered to indicate that the timing of injection INJ can no further be advanced to prevent the engine from knocking.  
         [0134]     Accordingly, correction value SAK(I) is calculated as SAK(I−1)−C and thus reduced (S 306 ). In that case, correction value SAK(I) necessarily attains a value no more than upper limit value SAK(X) (YES at S 310 ). Accordingly, the base timing of spark SAB plus the calculated correction value SAK(I) is calculated (S 314 ) to retard the timing of spark SA.  
         [0135]     In contrast, correction value INJK(I) different from upper limit value INJK(X) (YES at S 304 ), i.e., correction value INJK(I) smaller than upper limit value INJK(X) is considered to indicate that the timing of injection INJ can be advanced to prevent the engine from knocking.  
         [0136]     In that case, to introduce spark advance, correction value SAK(I) is calculated as SAK(I−1)+D and thus increased (S 308 ). If the calculated correction value SAK(I) is no more than upper limit value SAK(X) (YES at S 310 ), the base timing of spark SAB plus the calculated correction value SAK(I) is calculated to obtain a timing of spark SA (S 314 ). In that case, a spark advance is introduced. This can prevent engine  100  from providing an output (or torque) reduced as spark retard is introduced.  
         [0137]     If the timing of spark SA is advanced more than required, the air fuel mixture&#39;s combustion may be impaired resulting in engine  100  providing a reduced output (or torque). To prevent advance more than required, if correction value SAK(I) is greater than upper limit value SAK(X) (NO at S 310 ), upper limit value SAK(X) is set to correction value SAK(I) (S 312 ) and thus limited. This can prevent a timing of spark to be advanced more than required and hence engine  100  from providing a reduced output (or torque). Note that in addition to limiting correction value SAK(I) to be no more than upper limit value SAK(X), correction value SAK(I) may be limited to be no less than lower limit value SAK(Y).  
         [0138]     Thus when ECU  200  implementing the control device in accordance with the present embodiment detects that an engine knocks, and correction value INJK(I) applied to correct a timing of injection is equal to upper limit value INJK(X), ECU  200  introduces spark retard. This can further prevent the engine from knocking when a timing of injection cannot be controlled to prevent the engine from knocking.  
       Other Embodiment  
       [0139]     In the first and second embodiments, fuel injection advance is introduced at an intake stroke. Alternatively, fuel may be injected twice, i.e., at intake and compression strokes, and if the engine knocks, fuel injection retard may be introduced at the compression stroke, and if the engine does not knock, fuel injection advance may be introduced at the compression stroke. This can also provide an effect similar to that achieved in the first embodiment.  
         [0140]     Furthermore, if fuel injection retard is introduced at the compression stroke, an upper limit (a limit associated with advance) and a lower limit (a limit associated with retard) of timing of injection may be provided. This can also provide an effect similar to that achieved in the first embodiment.  
         [0141]     Furthermore, if such upper and lower limits are introduced for the timing of injection at the compression stroke, and the engine knocks and the timing of injection corresponds to the lower limit value, spark retard may be introduced to prevent the engine from knocking. This can also provide an effect similar to that achieved by the third embodiment.  
         [0142]     Furthermore, if the engine knocks, then in addition to introduce fuel injection retard at the compression stroke the fuel may also be injected at the compression stroke in an increased amount (or in an amount increased in ratio), and if the engine does not knock, the fuel may be injected at the compression stroke in a reduced amount (or in an amount reduced in ratio). This can also provides an effect similar to that achieved by the first embodiment.  
         [0143]     Furthermore, if the fuel is injected at the compression stroke in an increased amount, the amount may be provided with upper and lower limits. This can also provide an effect similar to that achieved by the first embodiment.  
         [0144]     Furthermore, if such upper and lower limits are introduced for the amount of fuel injected at the compression stroke, and the engine knocks and the timing of injection corresponds to the upper limit value, spark retard may be introduced to prevent the engine from knocking. This can also provide an effect similar to that achieved by the third embodiment.  
         [0145]     Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.