Abstract:
An improved method and system for the control of an engine fuel injection system. The control senses the speed variations either during a portion of a complete cycle and a complete cycle and/or from cycle to cycle in order to determine the load on the engine from preprogrammed maps based upon the engine characteristics. From this load and the speed reading, it is possible to obtain the desired engine fuel injection control. This not only reduces the costs of the system by reducing the number of sensors, but also permits adjustments to be made more rapidly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of the copending application entitled “ENGINE CONTROL METHOD AND APPARATUS”, Ser. No. 09/682,457, Filed Sep. 5, 2001 and assigned to the assignee hereof. 
    
    
     BACKGROUND OF INVENTION 
     This invention relates to an engine fuel injection system and control method and more particularly to an improved, simplified, highly effective and yet low cost arrangement for such a system and control. 
     In internal combustion engines, a wide variety of systems and methodology are employed for engine fuel injection control. Generally, smaller and lower volume engine applications incorporate generally less sophisticated controls than those employed on larger production volume engines such as automotive engines. Even in the small displacement lower production volume engines, for example those used in motorcycles, the engine fuel injection control can become quite complicated. 
     For example and as shown in FIG. 1, the fuel injection control for a motorcycle engine is shown schematically. The control arrangement is intended to control the timing and duration of fuel injection from a fuel injector  21  associated with an internal combustion engine  22  that powers the motorcycle, which is not shown in this figure, but which may be of a construction as generally shown in FIG. 2. A control signal “i” is applied to the fuel injector  21  that is supplied with fuel from a fuel supply system, indicated generally at  23  by a fuel injection control circuit arrangement, indicated schematically at  24 . This fuel injection control circuit arrangement  24  receives the inputs from a number of engine-associated sensors. 
     These sensors include a crankcase rotational speed sensor  25  which may comprise a pulser coil and a throttle position sensor  26 , which is coupled to the throttle control mechanism for the engine  22  for controlling the position of a throttle valve  27  and inputs a signal to the control  24  indicative of engine load and/or operator demand. 
     Electrical power is provided to the injection control circuit arrangement  24  from a battery  28  through a main switch  29 . This battery power is applied to a power source circuit  30  of the fuel injection control circuit arrangement  24  and specifically to an electronic circuit  31  which may comprise a microprocessor. 
     The output from the engine speed sensor  25  is transmitted to a rotational speed detector circuit  32 , which counts the number of pulses generated in a time period so as to determine the rotational speed of the crankshaft of the engine  22 . 
     This outputs a speed signal N to a fuel injection timing and duration (amount) control determining circuit, indicated at  33 . In addition, the throttle position sensor  26  inputs a signal to a throttle position detector circuit  34 . This detector circuit  34  outputs a signal A to a throttle opening calculating circuit  35 . This, in turn, outputs a throttle angle position θ to the fuel injection timing and duration (amount) control circuit  33 . 
     From these inputs, the fuel injection timing and duration (amount) control circuit  33  outputs a signal at times determined from maps contained in a memory of the circuit  31  to an fuel injection timing and duration (amount) control circuit  36  to output a timed electrical output “i” of predetermined length to the fuel injector  21  for operating it in a well-known manner. 
     Various maps may be incorporated in the circuit  31  and to determine how long and when the fuel injection is varied in response to engine speed for given load as determined by the throttle opening circuit. There may be a family of such curves so as to vary the injection timing and duration in response to both throttle position and engine speed. 
     The introduced charge is then ignited by a spark plug  37  that is fired in any desired manner including that described in the aforenoted copending application, Ser. No. 09/682457. 
     Rather than using a throttle position sensor, load may be sensed by intake manifold vacuum. Either method, however, requires added sensors, transducers and circuitry. 
     It has been found that merely using engine speed and load as detected by something such as a throttle position or intake manifold vacuum sensor does not actually provide as good a control as desired. That is, these two factors by themselves may not be sufficient to provide the desired degree of control. 
     Although systems have been provided for automotive applications wherein more sophisticated controls are employed, this further adds to the cost of the system and does not always provide the optimum results. 
     There have also been other devices than throttle position sensors or vacuum sensors for sensing intake manifold vacuum for determining engine load. It also has been determined that engine load may be found by comparing engine speed from one revolution to another. However, these systems also tend to be complicated and do not lend themselves particularly low production volume, low cost vehicle applications. They also have the disadvantage of requiring a plurality of different types of sensors. 
     Other arrangements have been proposed wherein engine speed is measured for less than one complete revolution of the engine and variations from cycle to cycle have been employed to determine engine load. These systems, however, have for the most part, required multiple sensors and also require some delay from the sensed conditions before adjustment is being made. 
     It is, therefore, a principal object to this invention to provide an improved engine control system wherein the number of sensors employed for achieving optimum engine fuel injection control is substantially reduced. 
     It is a further object to this invention to provide an arrangement for controlling an engine fuel injection system utilizing only a single sensor and a single timing mark associated with a driven engine shaft so as to substantially reduce the costs, without significantly decreasing the efficiency or the obtaining of an optimum control. 
     SUMMARY OF INVENTION 
     A first feature of this invention is adapted to be embodied in an internal combustion engine fuel injection control system. The engine has a driven shaft and a sensor arrangement is associated with the driven shaft for sensing the instantaneous rotational speed of the driven shaft during the rotation of the driven shaft for less than a complete rotation and for sensing the rotational speed of the driven shaft for a complete revolution that includes the measured less than complete rotation. In accordance with the apparatus, the engine fuel injection system is controlled from these measurements. 
     Another feature of the invention is adapted to be embodied in a four-cycle internal combustion engine fuel injection control. In accordance with the apparatus, the engine has a driven shaft and a sensor arrangement is associated with the driven shaft for sensing the rotational speed of the driven shaft. The rotational speed of the driven shaft during a revolution containing a compression stroke and during a revolution containing an exhaust stroke is made. The engine fuel injection is controlled from these measurements. 
     Another feature of the invention is adapted to be embodied in a fuel injections system for an internal combustion engine. The engine has a driven shaft and sensor is associated with the driven shaft for sensing two rotational conditions of the driven shaft during a first rotation thereof. The same two rotational conditions are sensed during the immediately succeeding rotation of the driven shaft and the engine fuel injection system is controlled on the third rotation of the driven shaft from these measurements. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a partially schematic view showing a prior art type of engine fuel injection control system. 
     FIG. 2 is a side elevational view of the type vehicle which the prior art system can be utilized and also which can utilize the invention. 
     FIG. 3 is a schematic view, in part similar to FIG.  1 . but shows the construction in accordance with an embodiment of the invention. 
     FIG. 4 is a view showing the timing sensor associated with the engine shaft for the fuel injection control system. 
     FIG. 5 is a schematic view showing the method of practicing the invention. 
     FIG. 6 is a block diagram showing a control routine, which may be utilized to practice the invention. 
     FIG. 7 is an enlarged view of the load determination portion of the diagram of FIG.  5 . 
     FIG. 8 is a graphical view showing the three-dimensional map utilized to determine the engine injection control with respect to engine load and engine speed in FIG.  5 . 
     FIG. 9 is a graphical view showing how the shaft speed varies during the compression stroke with engine speed and load. 
     FIG. 10 shows the same condition but on the exhaust stroke. 
     FIG. 11 is a graphical view showing the difference between the speed variations on the compression and exhaust strokes. 
    
    
     DETAILED DESCRIPTION 
     Referring now in detail to the drawings and initially to FIG. 2, a motorcycle constructed and operated in accordance with the invention is identified generally by the reference numeral  51 . It is to be understood that this specific application for the invention is only a typical one with which the invention may be utilized. A motorcycle is chosen at the exemplary embodiment because the invention, as should be apparent from the foregoing description, has particular utility in conjunction with relatively small, low production volume engines. However, it should also be apparent that the simplicity of the invention lends itself to use with other applications such as automotive application due to the improvement in performance without significant cost penalties. 
     The motorcycle  51  is comprised of a frame assembly, indicated generally by the reference numeral  52 , that dirigibly supports a front wheel  53  on a front fork  54  that is steered by a handle bar assembly  55  in a well-known manner. 
     A rear wheel  56  is supported for suspension movement relative to the frame  52  by means that includes a trailing arm assembly  57 . An engine, indicated generally by the reference numeral  58 , and having a combined crankcase transmission assembly  59  is suitably suspended in the frame  52  and drives the rear wheel  56  through a suitable drive arrangement. 
     The engine  58  has a throttle body  61  that controls the air flow to the engine  58 . A throttle valve is associated with this throttle body  61  and is operated by a twist grip throttle control  62  mounted on the handle bar  55 . With conventional systems, but not necessary with this invention, a throttle position sensor  63  is associated with the throttle valve shaft of this throttle valve. 
     As with the prior art constructions as previously described, a fuel injection system including the fuel injector  21  and fuel supply system  23  that includes a fuel tank  64  is provided for supplying a fuel charge to the engine  58 . The fuel injector  21  may be of the manifold or direct injection type. The engine  58  is provided with one or more spark plugs  65  (FIG. 3) that are fired by any desired type of ignition system. 
     The combustion gases are discharged from the engine exhaust port through an exhaust pipe  66  and muffler  67 , which has an atmospheric discharge. 
     The engine  58  in accordance with the illustrated embodiment operates on the four stroke principal, but as will become apparent to those skilled in the art, the invention can also be utilized with two cycle engines. 
     A seat  68  is positioned on the frame assembly  52  to the rear of the fuel tank  64  for accommodating the rider in a well-known manner. 
     Referring now primarily to FIGS. 3 and 4, the control system for controlling the engine fuel injection system and specifically the operation of the fuel injector  21  will be described in more detail. The engine  58  has a crankshaft  69  to which a flywheel  71  is affixed for rotation in a known manner. Although the invention is depicted in association with a crankshaft positioned sensor, it may be associated with any other shaft that is driven by the engine in timed relation. 
     A pulser type sensor  72  is associated with the flywheel  71  and specifically with a timing mark  73  affixed to its outer peripheral surface. The timing mark  73  has a leading edge  74  and a trailing edge  75  which, when passing the sensor  72  will output pulses that can be measured so as to measure the time it takes the timing mark  73  to pass the sensor  72 . This constitutes an instantaneous rotational speed for the engine  58  during a portion of a complete rotation. 
     The timing mark  73  is considerably wider, in accordance with the invention, than those normally used. Such widening is not necessarily required, but can improve the control. For example the width of the mark  73  may be equal to 60° of crankshaft rotation. The timing mark is set so that it will first trigger a pulse as the engine begins to approach top dead center (TDC) position and another pulse after the crankshaft is at or near top dead center. The specific angles may vary depending upon the particular application. 
     Nevertheless, because of the four-stroke operation, these pulses are generated at the end of the compression and exhaust strokes. Prior art methods may have utilized speed measurements during the power stroke, but it has been found that the compression and exhaust stroke are much more accurate in providing an indication of engine load and this constitutes one of the features of the invention. 
     With a two cycle engine the two measurements per revolution will provide adequate information for engine control on the next revolution. 
     As seen in FIG. 3, the output from the sensor  72  is delivered to an engine fuel injection system control device  76 , which contains a fuel injection circuit  77  that can be basically a conventional system, which outputs a signal, “i” to the fuel injector  21  for controlling the time of initiation of injection as well as the amount of fuel injected in a known manner. 
     This engine fuel injection control system  76  is powered with electrical power from a battery  79  through a main switch  81 . 
     The output from the sensor  72  is transmitted to a rotational speed detection circuit  82 , which outputs a signal N indicative of the rotational speed of the engine during each complete revolution cycle. In addition, the outputs from the leading and trailing edges  74  and  75  of the timing mark  73  registered on the sensor  72  are transmitted to a degree of rotational variation detector circuit  83 . This circuit  83  outputs a signal “R” indicative of the speed difference to a load calculation circuit  84 . 
     In the described embodiment, the flywheel  71  may be formed of a magnetic material, and the sensor or coil  72  faces the rotational locus of the timing mark  73 . In this case, opposite ends of the timing mark  73  are detected from changes in magnetic resistance in the magnetic path passing through the iron core of the coil  72 . Alternatively the timing mark  73  may be formed from permanent magnets fixed on the flywheel  71  at positions a given angle away from each other, and the sensor may be a magnetic sensor such as a Hall element for detecting passage of the permanent magnets. Alternatively, the mark may be a slit, which may be detected optically with an LED and a light receiving element. 
     The load calculating output circuit operates so as to determine a load factor that is derived from as map shown in FIG.  7 . This output is delivered to an injection timing and rate determination circuit  85  which operates in accordance with the control routine shown in FIGS. 5 and 6 so as to output a signal P to the fuel injection circuit  77  for operating the fuel injector  65  at the appropriate time and duration for the engine speed and engine load. 
     The circuit portions  82 ,  83 ,  84  and  85  are all located within a CPU  86  of the engine fuel injection control system  76 . 
     Referring now primarily to FIG.  5  and later to FIG. 6, the basic control method used in connection with the invention is to measure revolution to revolution changes in speed “R” will be described. From that difference it is possible to determine engine load. Then by consulting a map of injection control timing and duration, the appropriate fuel injection control can be determined. 
     FIG. 5 shows schematically how the output from the rotational sensor, in the specific example the coil  72  outputs its signal to the circuit portions  82  and  83  to determine the degree of rotational variation R. A first method to determine the degree of rotational variation R is one in which a ratio of detection time “t” of the projection rotation during a portion of a complete revolution to the period T for a complete rotation including that of the time period t. From these two measurements a ratio is determined and the ratio (t/T)≡R is defined as a degree of rotational variation. This method permits adjustment of the engine fuel injection control on the very next rotation. This method can be used with both two and four cycle engines. 
     A second method to determine the degree of rotational variation R is one in which ratios (t/T) determined by the first method are determined for both the compression and the exhaust stroke (ie. two crankshaft rotations). This method is preferably used in four cycle engines. Then the difference between the ratios is defined as a degree of variation. That is, the difference (R n−1 −R n )=D between a ratio (t n−1 /T n−1 )=R n−1  for the compression stroke and a ratio (t n /T n )=R n  for the exhaust stroke are determined for each compression or exhaust stroke. The difference D is determined as a degree of variation. These methods are shown in the upper right hand box of FIG.  5 . 
     FIG. 9 shows the ratio R n−1 =(t n−1 /T n−1 ) for the compression stroke in % at varying torques or loading at 40, 80, 120, 160 200 and 240 Newton meters (N-m). For example, if there is no rotational variation, (60°/360°)=0.167 and thus, the ratio is 16.7%. However, the rotational speed of the crankshaft drops on the compression stroke near Top Dead Center (TDC), so that the ratio R n−1  becomes large. As seen in FIG. 9, the ratio R n−1  and the rotational variation is larger for a smaller engine speeds N and decreases as N increases. Also as the load or torque increases, the curves shift upwardly because the variation increases. 
     FIG. 10 shows the ratio R n =(t n /T n ) for the exhaust stroke in % where an opposite condition prevails. That is rotational variation is smaller for a smaller engine speeds N and increases as N increases. Also, as the load or torque decreases, the curves shift downwardly because the variation decreases. 
     FIG. 11 shows the difference D=(R n−1 −R n ) between the ratio R n−1  for the compression stroke and the ratio R n  for the exhaust stroke, using FIG.  9  and FIG.  10 . Here, values of the rotational variation for every cycle measured during ten periods are averaged to improve the stability of the data. The degree-of-rotational variation detection circuit  83  repeats the foregoing calculation in synchronization with the crankshaft rotation. 
     The characteristics shown in FIG. 11 are measured on the engine in advance and stored in a memory of the microcomputer  76 . They are stored, for example, as a three-dimensional conversion map shown in FIG.  7 . The load calculation circuit  84  determines load (load Nm on the rear wheel) from the conversion map in FIG. 7, using the degree of rotational variation D determined by the degree-of-rotational variation detection circuit  83 , and engine speed N. This determination is shown in the middle right hand box in FIG.  5 . 
     Stored in advance in a memory of the microcomputer  76  is the three dimensional map shown in FIG. 8, depending on the specific engine. This map shows the relation between load L, engine speed N and injection amount “m”. The injection timing and rate determination circuit  85  determines injection amount m from the map in FIG. 8, using load L and engine speed N determined by the load calculation circuit  84 . Injection timing is determined in a similar manner. An injection signal P corresponding to the injection timing and amount is sent to the injection circuit  77 . As already noted, the injection circuit  77  causes the fuel injector to inject. This is shown in the lower right hand box of FIG.  5 . 
     A preferred operation of this embodiment will be described with reference to FIG.  6 . First, if at the Step S 1  it is determined that the engine is running in an idling state, as it will immediately after a warm start up, injection amount m is set to a fixed value m1 at the step S 2  and injection control is performed at the step S 3 . The program then repeats to the step S 1 . 
     If the engine  58  is found not to be in an idling state at the step S 1 , the degree-of-rotational variation detection circuit  83  detects the degree of rotational variation D at the step S 4 . The microcomputer in the electronic circuit  36  determines whether or not the degree of variation D is within a given range of D m  to D M  at the step S 5 . If the variation is out of this range, the injection amount is set to a fixed value m2 or m3 at either the step S 6  or S 7 . 
     The fixed values of m1, m2 and m3 are set to avoid errors under small deviations in D to avoid the effects of electrical noise. 
     If within this range of D M -D m , the load calculation circuit  84  determines load L using engine speed N determined by the rotational speed detection circuit  82  at the step S 8  and looking up the load L from the conversion map of FIG. 7 at the step S 9 . 
     The fuel injection determination circuit  85  then determines injection amount m at the step S 10  using this load L and engine speed N and looking up this value from the conversion map in FIG.  8 . The fuel injection determination circuit  85  then sends an ignition signal P corresponding to the read fuel injection amount m to the fuel injector  65  to be operated at the step S 3 . 
     As has been noted, the timing of fuel injection initiation can be determined in a like manner. 
     Thus, from the foregoing description should be readily apparent that the described method and structure provides a very simple and low cost yet highly effective system for controlling an engine fuel injection system. Also, the system is capable of being used with either two or four cycle engines. Of course, further changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.