Abstract:
A number of embodiments of ignition systems wherein reverse rotation also known as kickback is detected particularly upon engine starting and stopped until the condition has been cleared and forward running is assured.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to an ignition system for an internal combustion engine and more particularly to an ignition system that insures against kick back or reverse rotation from occurring during initial engine start up.  
         [0002]     There is disclosed in our co-pending application Ser. No. 10/605,843, filed Oct. 30, 2003, based upon Japanese Application Serial Number 2002-342256 and assigned to the assignee hereof an ignition system that is designed to prevent reverse rotation commonly called “kick back” upon engine starting by detecting a condition where engine speed starts do decrease after the starting operation has begun by disabling the continued ignition until another starting operation has begun.  
         [0003]     However that system has a disadvantage as may be best understood by reference to  FIGS. 1-3 .  FIG. 1  illustrates the relevant portion of the engine and its ignition system. As seen in this figure, a shaft of the engine such as its crankshaft  11  or any other shaft that rotates in timed relation to the crankshaft has formed on its peripheral surface a timing mark  12  that has a predetermined circumferential length between its leading edge A and its trailing edge B. This circumferential length may be in any desired range, normally in the range of 30 to 60 degrees.  
         [0004]     Cooperating with this timing mark  12  is a sensor  13  of any known construction that is utilized to provide a signal that is transmitted to an ignition system, not shown in these figures. but which will be described in more detail later by reference to the remaining figures that illustrate preferred embodiments of the invention.  
         [0005]     The sensor  13  comprises normally a core  13   a  around which a coil  13   b  is wound to produce a pulse signal as shown in  FIGS. 2 and 3  as the shaft  11  rotates and the leading and trailing edges A and B pass. The arrow R indicates the normal rotational direction of the shaft  11 . The first generated pulse is positive while the second is negative regardless of the direction of rotation.  
         [0006]     There may be two modes of reverse rotation in which the engine rotates in reverse after the leading edge A of the projection  12  faces and passes by the core  13   a . One of these occurs before the trailing end B leaves the sensor core  13   a  (in-projection-reverse rotation). The other (out-of-projection reverse rotation) occurs after the trailing end B leaves the sensor core  13   a  but before top dead center is reached.  
         [0007]      FIG. 2  shows the pulse waveform in the in-projection reverse rotation mode. In the normal rotation state during cranking for starting the engine, a rise-up pulse (positive pulse) is produced when the fore-end A of the timing mark is detected by the pulser coil  13  for each rotation of the crankshaft, followed by a decay pulse (negative pulse) when the trailing end B of the projection is detected. When reverse rotation is about to occur, the rotation of the crankshaft slows down gradually. When the rotation speed becomes zero after the pulser coil  13  detects the fore-end A of the timing mark  12  somewhere in the position before reaching the trailing end B and thereafter reverse rotation occurs.  
         [0008]     Thus when the leading end A of the timing mark  12  again passes by the detection core  13   a  of the pulser coil  13  after starting reverse rotation, a decay pulse (negative pulse) is produced from the same end A of the timing mark  12 . However, the output of the generator decreases due to a decrease in the crankshaft rotation. In accordance with the metholodgy of the aforenoted co-pending application, the reverse rotation of the crankshaft  11  is detected from the decrease in the generator output.  
         [0009]     In response to this, an ignition prohibiting signal is given out. As a result, even if the negative pulse is given out the leading end A of the timing mark  12  the ignition signals are prohibited. Thus, if the engine misfires, no combustion occurs in the reverse rotating direction, and kickback is prevented from occurring.  
         [0010]     As described, the kickback is prevented from occurring by prohibiting ignition during reverse rotation and the crankshaft  11  will stop rotating. After that, in order to permit re-starting the engine by cranking, the ignition prohibiting state must be cleared. This is done in the aforenoted co-pending application by clearing the ignition prohibiting state upon the input of a first positive pulse. After that, when the trailing end B of the timing mark  12  is detected and a negative pulse is produced, ignition signals are permitted and combustion occurs for the normal rotation of the engine.  
         [0011]      FIG. 3  shows the pulse waveform in the out-of-projection reverse rotation. In the normal rotation state during cranking for starting the engine, like the situation of  FIG. 2 , the fore-end A of the projection is detected for every rotation of the crankshaft and a rise-up pulse (positive pulse) is produced, then a decay pulse (negative pulse) is produced when the trailing end B of the timing mark  12  is detected.  
         [0012]     If the rotation speed of the crankshaft gradually slows down and the reverse rotation is about to occur, the leading end A of the timing mark  12  is detected and the timing mark  12  slowly passes by the detecting core  13   a  of the pulser coil  13 . Subsequently the trailing end B passes by the detecting position  13   a  and produces a pulse indicated at  14 . Here, the rotation speed of the crankshaft  11 , when it is low, may becomes zero before the trailing end B reaches the top dead center and the crankshaft  11  will turns in reverse.  
         [0013]     As a result, the trailing end B of the timing mark  12  that has once passes by the detecting core  13   a  of the pulser coil  13 , returns to the detecting core  13   a , and is detected to produce a positive pulse  15 .  
         [0014]     Subsequently, when the leading end A of the timing mark  12  passes by the detecting core  13   a , a negative pulse  16  is produced. Also this out-of-projection reverse rotation, like the situation shown in  FIG. 2 , is detected from the decrease in the output of the generator, and ignition is prohibited to prevent kickback from occurring after the reverse rotation occurs.  
         [0015]     However and as described above, because the ignition prohibiting state is reset by cranking again after the stop of the crankshaft rotation, ignition prohibition is cleared by the first positive pulse  15  produced after the reverse rotation. Therefore, when the projection end A is detected and a negative pulse  16  is produced after that, ignition signals are given out. Thus rather than preventing reverse rotation, the engine may continue to operate in reverse.  
         [0016]     In view of these potential problems it is a principal object of this invention to provide a kickback preventing apparatus and method that is effective to rapidly detect a reverse rotation operation during starting and prevent further reverse rotation by positively preventing ignition and in particular to reliably prevent kickbacks from occurring in the out-of-projection reverse rotation.  
       SUMMARY OF THE INVENTION  
       [0017]     This invention is adapted to be embodied in a kickback preventing ignition system for an internal combustion engine having a rotating shaft and a timing mark rotating with the shaft and having circumferentially spaced leading and trailing ends. A sensor is associated with the timing mark and is adapted to produce pulses when said each of the leading and trailing ends pass under rotation of a shaft. A processor determining that reverse rotation may be occurring based on a sensed decrease in value of at least one of the pulses and prohibits ignition of the engine and reestablishes ignition upon the production of a pulse from the leading edge of the timing mark unless a predetermined time period has elapsed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a partially schematic view of a timing and kickback sensor to illustrate the problems with the prior art and to describe the types of kick back that may occur on engine starting.  
         [0019]      FIG. 2  is a wave form of the sensor outputs during a situation where reverse rotation occurs during the time when the timing mark is in registry with the timing mark (on-projection reverse rotation).  
         [0020]      FIG. 3  is a wave form of the sensor outputs during a situation where reverse rotation occurs during the time when the timing mark is not in registry with the timing mark (off-projection reverse rotation).  
         [0021]      FIG. 4  is a partially schematic view of a first circuit and construction for precluding kickback (reverse rotation).  
         [0022]      FIG. 5  is a partially schematic view, in part similar to  FIG. 1 , and shows a second embodiment of a first circuit and construction for precluding kickback.  
         [0023]      FIG. 5  is a partially schematic view, in part similar to  FIG. 1 , and shows a second embodiment of a first circuit and construction for precluding kickback.  
         [0024]      FIG. 6  is a partially schematic view, in part similar to  FIGS. 1 and 5 , and shows a third embodiment of circuit and construction for precluding kickback.  
         [0025]      FIG. 7  is a series of traces showing the theory of operation of the embodiments of  FIGS. 4, 5  and  6 .  
         [0026]      FIG. 8  is a partially schematic view, in part similar to  FIGS. 1, 5  and  6  and shows a third embodiment of circuit and construction for precluding kickback.  
         [0027]      FIG. 9  is a series of traces, in part similar to  FIG. 7 , showing the theory of operation of the embodiment of  FIG. 8 .  
         [0028]      FIG. 10  is a partially schematic view, in part similar to  FIGS. 1, 5 ,  6  and  8  and shows a forth embodiment of circuit and construction for precluding kickback that combines the structures and purposes of the previous embodiments. 
     
    
     DETAILED DESCRIPTION  
       [0029]      FIG. 4  shows a circuit constitution for determining reverse rotation in accordance with a first embodiment of the invention in a partially schematic form. This circuit includes a three-phase generator  21  provided at an end of a crankshaft (not shown) of an associated engine in a manner well known in the art. The generator  21  has three-phase coils as a portion of a stator facing a magnet arrangement positioned on the inside surface of a rotor that generally comprises a flywheel, attached to the end of the crankshaft of the engine. Three-phase output terminals U, V, and W are connected through a regulator  22  for rectification and prevention of over-voltage to a battery  23 .  
         [0030]     A rotor (not shown) having a timing mark as aforenoted by reference to  FIG. 1  for detecting rotary angle is attached to the crankshaft. A pulser coil or sensor  13  for detecting the timing mark is provided opposite the outer side of the rotor, as was described in  FIG. 1 . The pulser coil  13  detects both ends A and B of the timing mark, extending for example by an arcuate angle of about 60 degrees on the side face of the rotor. These are sensed as changes in magnetic flux and produce positive and negative pulser signals, one each per rotation. The positive and negative pulser signals are the rise-up pulse (positive pulse) and decay pulse (negative pulse), respectively, as aforenoted.  
         [0031]     The pulser coil  13  outputs these pulses to an ignition system  24  for controlling ignition of the engine. This ignition system  24  consists of a power source circuit  25  connected to the battery  23 , a step-up circuit  26  for obtaining a specified ignition voltage, an ignition circuit  27  connected to the pulser coil  13 , and a kickback preventing circuit  28 . The ignition circuit  27  applies the ignition voltage to an ignition coil  30  at an appropriate crank angle position in accordance with any desired control routine in response to the pulser signal coming from the pulser coil  13  and other desired engine running conditions as sensed in desired manners.  
         [0032]     The kickback preventing circuit  28  is comprised of a pulser input circuit  29 , a reverse rotation determination circuit  31 , and a generator output-input circuit  32 . The pulser input circuit  29  is connected to the pulser coil  13  through a terminal A to receive pulser signals. The generator output-input circuit  32  is connected through terminals B and C to any two-phase terminals (V and W terminals in this example) of the generator  21  and receives output voltage of the generator  21 .  
         [0033]     The reverse rotation determination circuit  31 , as described above in reference to  FIGS. 1-3 , in either case of the in-projection reverse rotation or out-of-projection reverse rotation, determines reverse rotation on the basis of generator voltage from the pulser signal coming from the pulser input circuit  29  and the generator voltage coming from the generator output-input circuit  32 . When the generator output decreases below a specified value and the engine turns again in reverse and generator output starts rising an ignition permitting signal or ignition prohibiting signal is transmitted to the ignition circuit  27  through a terminal D. How this is determined and executed will be described later by reference to  FIG. 7 .  
         [0034]      FIG. 5  shows a circuit construction of an embodiment of the invention.  FIG. 6  shows a circuit constitution in which the embodiment of the reverse rotation misfiring circuit shown in  FIG. 5  is built in the kickback preventing circuit shown in  FIG. 4 .  
         [0035]     Referring now in detail to  FIGS. 5 and 6 , a first reverse rotation misfiring circuit  33  is comprised of a MAG output-input circuit  34  for receiving coil output (MAG output) from the generator  21 , an MAG output count circuit  35  for counting the number of the MAG outputs, and an ignition control circuit  36  for controlling ignition according to the counted number of the MAG outputs.  
         [0036]     If the MAG output counted number from the circuit  35  after a negative pulse from the pulser coil  13  is detected is not greater than a specified value (for example four in the case of  FIG. 7 ) the ignition control circuit  36  gives out an ignition prohibiting signal. This ignition prohibiting signal overrides a prohibition clearing signal produced by the input of a positive pulse for resetting an ignition prohibiting signal during reverse rotation.  
         [0037]     Therefore, even if a positive pulse signal for clearing the ignition prohibition is inputted during out-of-projection reverse rotation, the input signal is overridden and the ignition prohibiting state is maintained until the number of the MAG outputs becomes four, so that kickback is reliably prevented from occurring.  
         [0038]     Since in in-projection reverse rotation, the reverse rotation determination circuit  31  gives out an ignition prohibiting signal, ignition by the negative pulse when the timing mark leaves immediately after the occurrence of reverse rotation within the timing mark range is prohibited, no kickback occurs and the engine stops.  
         [0039]      FIG. 7  shows waveforms as the reverse rotation preventing circuit of  FIG. 5  works. This example shows the situation in out-of-projection reverse rotation. The trace a in this figure shows pulser coil output. In normal rotation as shown above in  FIG. 3 , the pulser coil detects the ends A and B of the timing mark  21  around the flywheel, and gives out positive and negative outputs, one each per rotation. Using this negative pulse, as shown in trace b, the ignition capacitor discharges to ignite the combustion chamber of the engine.  
         [0040]     When out-of-projection reverse rotation occurs, as shown by trace a, the timing mark end B, having produced a negative pulse as it passes by the pulser coil immediately before turning in reverse, turns back, and produces a positive pulse  24  in reverse rotation state, and then a negative pulse  25  is produced with the timing mark end A.  
         [0041]     The MAG outputs, as shown by the trace d are produced six in number per rotation. According to this invention, the MAG outputs are counted and an ignition prohibiting signal is produced until the count reaches five. Thus as shown by trace c, ignition is prohibited at Hi and permitted at Lo. Therefore, when the count of coil outputs is four or less, ignition remains in prohibited state.  
         [0042]     When the out-of-projection reverse rotation occurs, ignition is prohibited for the period from the moment a negative pulse  14  is produced immediately before reverse rotation to the moment the number of MAG outputs reaches four. Therefore, even if the negative pulse  15  is produced after reverse rotation, an ignition prohibition clearing signal is not outputted and ignition remains prohibited. Therefore, ignition does not occur even if a next negative pulse  16  is produced.  
         [0043]      FIG. 8  is a circuit diagram of another embodiment of the invention and  FIG. 9  is a drawing for explaining its operation. In this embodiment where components have substantially the same construction as those already described, they have been identified by the same reference numerals and will be described again only where necessary to understand the construction and operation of this embodiment.  
         [0044]     The kickback preventing circuit  28 , as described with  FIG. 7 , determines reverse rotation based on the generator output and thereafter prohibits ignition. When the engine stops after the ignition is prohibited and a positive pulse is inputted later at the time of re-starting, prohibition of ignition is cleared and ignition is made to occur when a negative pulse is inputted next.  
         [0045]     A second reverse rotation misfiring circuit  37  of this embodiment is comprised of an ignition prohibition signal input circuit  38 , and an ignition prohibition signal output time determination circuit  39 . The ignition prohibition signal input circuit  38  is connected to the reverse rotation determination circuit  31  to receive an input of ignition prohibiting signal when reverse rotation is determined and also receives an ignition prohibition clearing signal caused by a next input of a positive pulse.  
         [0046]     The ignition prohibition signal output time determination circuit  39  measures the time of the ignition prohibiting state on the basis of the ignition prohibiting signal from the reverse rotation determination circuit  37  inputted to the ignition prohibition signal input circuit  38  and its clearing signal. When the ignition prohibition time is shorter than a specified value, an ignition prohibiting signal is produced to maintain the ignition prohibiting state. In other words, even if reverse rotation is determined with the reverse rotation determination circuit  31  of the kickback preventing circuit  28 , if an ignition prohibiting signal is given off, and then ignition prohibition is cleared by an input of a positive pulse, it is determined to be in the midst of reverse rotation when the positive pulse is inputted after a short period of time, and ignition prohibition is maintained.  
         [0047]     This will be described in reference to  FIG. 9 , which shows an example of out-of-projection reverse rotation. In normal rotation as shown by trace (a) the pulser coil detects the ends A and B ( FIG. 8 ) of the timing mark around the flywheel and gives out positive and negative outputs, one each per rotation. By this negative pulse, the ignition capacitor discharges to ignite the combustion chamber of the engine.  
         [0048]     When out-of-projection reverse rotation occurs, the timing mark end B having produced a negative pulse  14  as it passes by the pulser coil  13  immediately before turning in reverse, turns back, produces a positive pulse  15  in reverse rotation state, and then a negative pulse  16  is produced with the timing mark end A.  
         [0049]     This reverse rotation, as shown by trace (b) is detected with the kickback preventing circuit  28  and the ignition prohibiting state is brought about simultaneously with the detection of reverse rotation. After that, ignition prohibition is cleared by the input of the positive pulse  15  caused by the timing mark end B. The time t of the ignition prohibiting state up to its clearing is detected with the reverse rotation misfiring circuit  37  of this embodiment. If the detected time t is shorter than a specified time, as shown by trace(c), an ignition prohibition signal is given out simultaneously with the clearing of the ignition prohibition to maintain the ignition prohibiting state. Therefore, even if the negative pulse  16  is inputted as caused by the timing mark end A in the reverse rotation state, ignition is not made, and kickback is reliably prevented from occurring.  
         [0050]      FIG. 10  is a schematic circuit diagram of another embodiment of the invention that employs certain components of previously described embodiments. Where that is the case those components are identified by the same reference numerals and those components and their operation need not be described as the foregoing descriptions should permit those skilled in the art to practice the invention of this embodiment.  
         [0051]     This embodiment is comprised of a combination of the kickback preventing circuit  28  of the embodiment of  FIG. 6 , the first reverse rotation misfiring circuit  33  of  FIG. 6 , and the second reverse rotation misfiring circuit  37  of  FIG. 9 . Such a circuit constitution reliably detects reverse rotation of any mode and prohibits ignition.  
         [0052]     Thus from the foregoing descriptions it should be readily apparent that several embodiments of circuits and methods have been described that quickly and reliably detect reverse rotation or kickback and prevent its continuation while permitting normal resumption of ignition control once the reverse rotation has been stopped. Of course those skilled in the art will readily understand that the described embodiments are only exemplary of forms that the invention may take and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.