Patent Publication Number: US-5022363-A

Title: Positive starting circuit

Description:
This is a division of application Ser. No. 07/288,729, filed Dec. 22, 1988, now U.S. Pat. No. 4,951,620. 
    
    
     BACKGROUND AND SUMMARY 
     The present invention relates to starting circuitry for a two-cycle internal combustion engine. 
     The invention addresses problems of false starting, wherein the starter kicks-out upon ignition during initial cranking of the engine, but then the engine ceases running, thus requiring re-engagement of the starter to start the engine, and sometimes repeated restart attempts. It has been found that this false starting phenomenon is due to residual combustible charge in a cylinder which is ignited by the ignition circuit and causes kick-out disengagement of the starter from the flywheel, but wherein the following cylinder does not have a combustible charge, and hence the engine ceases running. 
     Upon recognizing the source of the problem as above noted, the present invention provides a simple solution by disabling ignition for a delay interval upon initial cranking of the engine such that ignition of any residual combustible charge in a cylinder is prevented during initial cranking. The delay interval is chosen to be long enough to permit sufficient combustible charge to be developed in the remaining cylinders before ignition is enabled. This interval is preferably about one-half second. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a circuit diagram illustrating a positive starting system in accordance with the invention. 
     FIG. 2 shows an alternate embodiment. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a multicylinder two-cycle internal combustion engine 10 having a crankshaft 12 and flywheel 14 cranked by starter gear 16 of starter motor 18 upon energization of start solenoid 20. Upon ignition of a combustible charge in an engine cylinder, the starter is kicked-out, i.e. starter gear 16 retracts out of engagement with flywheel 14, all as is well known. 
     It has been found that false starting during initial cranking of the engine is due to a residual combustible charge in a cylinder which is ignited by the ignition circuit and causes kick-out of the starter, and wherein the following cylinder does not have a combustible charge and the engine ceases running, thus requiring re-engagement of the starter to start the engine. In the present invention, this problem is solved by disabling the ignition at initial cranking of the engine to prevent ignition of any residual combustible charge in a cylinder. The delay interval is chosen to be long enough to permit sufficient combustible charge to be developed in the remaining cylinders before ignition is enabled. In the preferred embodiment, the delay interval is about one-half second, though other intervals may be used. 
     The positive starting circuit includes a kill switch 22 provided by an SCR connected between ground and the kill wire in the ignition circuit 24. Ignition kill switches so connected are known in the art, for example as shown in Fitzner U.S. Pat. No. 4,015,564, incorporated herein by reference. SCR 22 has a conductive state shorting the ignition circuit to ground to disable ignition, and a nonconductive state enabling ignition. An initiating circuit is provided by a connection circuit including conductor 26 connected to start solenoid 20 and responsive to initial cranking of the engine upon energization of the start solenoid and triggering switch 22 to its conductive state, disabling ignition. A delay circuit 28 responds to the trigger signal on conductor 26 of the initiating circuit to initiate a delay interval, and to trigger SCR 22 to its nonconductive state at the end of the delay interval, to thus enable ignition. 
     In operation, energization of start solenoid 20 provides a trigger signal on conductor 26 which is applied through protective diode 30 to timing circuit 28. Diode 30 protects the timing circuit against negative pulses upon de-energization of the start solenoid due to inductance thereof. Timing circuit 28 is a monostable multivibrator provided by a 555 IC timer chip, where manufacturer assigned pin number designations are shown to facilitate understanding. Multivibrator 28 has an output 32 connected through resistor 34 to control terminal or gate 36 of SCR 22 for controlling conduction thereof. Capacitor 38 is a noise filter. Resistor 34 is a current limiter. Input pins 4 and 8 of multivibrator 28 are connected through diode 30 to conductor 26 and respond to the triggering voltage therefrom to immediately drive output 32 high to thus turn on SCR 22 and disable ignition. The triggering signal from conductor 26 is also applied through resistors 40 and 42 to input pin 7 and to charging capacitor 44 connected to pin 7. The triggering signal is also applied through resistor 40 and diode 46 to input pin 5 having a voltage regulating zenner diode 48 connected thereto. Zenner diode 48 sets a reference voltage at input pin 5, and when capacitor 44 charges above such reference voltage, output pin 3 switches low to turn off SCR 22, thus enabling ignition. The charging time of capacitor 44 and the reference voltage set by zenner diode 48 determine the timing delay interval. Diode 46 provides reverse battery polarity protection. Capacitor 50 provides filtering. 
     FIG. 2 shows an alternate embodiment and uses like reference numerals from FIG. 1 where appropriate to facilitate clarity. Upon energization of the start solenoid, the triggering signal on conductor 26 through diode 30 and resistor 52 turns on SCR 22 to short the ignition circuit 24 to ground through diode 54, thus disabling ignition. The trigger signal is also applied through resistor 56 to provide a voltage at the collector of bipolar NPN transistor 58 which is regulated by the voltage regulator provided by zenner diode 60. This voltage is applied across resistor 62 to charge capacitor 64 and provide bias voltage to the base or control terminal 66 of transistor 58. When capacitor 64 charges above the base-emitter voltage of transistor 58, the latter turns on to provide a trigger signal to the gate or control terminal 68 of SCR 70 to turn the latter on and divert current away from gate 36 of SCR 22 and instead direct current from resistor 52 through SCR 70 to ground, whereby SCR 22 turns off, thus enabling ignition. The length of the timing delay interval is controlled by charging of capacitor 64. Resistor 72 references gate 68 of SCR 70 to ground so that the gate is not floating. Resistor 74 provides the same function for SCR 22. Capacitor 76 provides noise filtering. Diode 54 ensures a diode drop to ground from SCR 22 since SCR 70 is being used to clamp gate 36. 
     It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.