Ignition timing control system for light duty combustion engines

Abstract

A control system for a low cost, light duty combustion engine, where the control system generally utilizes an engine speed input signal and independent operating sequences to determine a desired ignition timing and air-to-fuel ratio for a combustible mixture. There are several independent operating sequences, each one of which is designed to optimally control the engine under certain conditions. These operating sequences include a Cranking sequence that commences after the engine is initially turned on, a Warm Up sequence which follows the Cranking sequence, a Normal Mode sequence which is the operational mode in control under typical operating conditions, an Acceleration sequence which is called upon if the Normal Mode ever detects an increase in engine speed exceeding a predetermined rate, a Come Down sequence which is initiated if the Normal Mode senses a sufficient engine speed followed by a certain decrease in speed, and a Recovery Bump sequence which the Normal Mode calls up if the engine speed dips below a predetermined level. By utilizing these operational sequences and an engine speed input signal, the control system of the present invention improves the engine performance and emissions of a low cost, light duty engine across a wide array of conditions.

1 . A control system for use with a light duty combustion engine, said system comprising: 
 an input coupled to an engine speed sensor for receiving an electronic speed signal representative of engine speed,    a first output coupled to an ignition device for providing that device with an electronic ignition signal that affects the ignition timing of the engine,    a second output coupled to a valve control device for providing that device with an electronic air/fuel signal that affects the air-to-fuel ratio of a combustible mixture being provided to the engine, and    an electronic processing device coupled to said input for receiving said speed signal, coupled to said first output for providing said ignition signal, and coupled to said second output for providing said air/fuel signal, wherein said processing device is capable of determining said ignition signal and said air/fuel signal according to an independent operating sequence that is capable of being selected by utilizing said speed signal.    
     
     
         2 . A control system as stated in  claim 1 , wherein said speed signal, a first charge signal for use with the ignition device, a second charge signal for use with the valve control device, and a power signal for supplying power to said electronic processing device are each provided by windings that are operatively coupled to magnetic sections of an engine flywheel.  
     
     
         3 . A control system as stated in  claim 2 , wherein said ignition signal causes a capacitive discharge of stored energy associated with said first charge signal to a primary ignition winding.  
     
     
         4 . A control system as stated in  claim 2 , wherein said air/fuel signal causes a capacitive discharge of stored energy associated with said second charge signal to a valve actuating solenoid.  
     
     
         5 . A control system as stated in  claim 1 , wherein said valve control device is a latching solenoid that controls the air-to-fuel ratio of the combustible mixture by controlling a carburetor air bleed unit.  
     
     
         6 . A control system as stated in  claim 1 , wherein said electronic processing device is controlled by an independent cranking sequence that is initiated following the starting of the engine and operates for a predetermined number of engine revolutions, said cranking sequence advances or retards the ignition timing a predetermined number of degrees and controls the air-to-fuel ratio of the combustible mixture.  
     
     
         7 . A control system as stated in  claim 6 , wherein said cranking sequence follows a predetermined number of ‘no-spark’ engine revolutions where said electronic processing device does not provide said ignition signal.  
     
     
         8 . A control system as stated in  claim 1 , wherein said electronic processing device is controlled by an independent warm up sequence that is initiated shortly after the engine is started, said warm up sequence is capable of utilizing said speed signal to advance the ignition timing at a first rate and retard the ignition timing at a second rate, and is capable of enriching the air-to-fuel ratio of the combustible mixture for a first number of engine revolutions and enleaning the combustible mixture for a second number of engine revolutions.  
     
     
         9 . A control system as stated in  claim 8 , wherein said system includes a second input coupled to an engine temperature sensor for receiving an electronic temperature signal representative of engine temperature, said warm up sequence is capable of controlling the air-to-fuel ratio of the combustible mixture for as long as said temperature signal is less than a predetermined value.  
     
     
         10 . A control system as stated in  claim 1 , wherein said independent operating sequence is an acceleration sequence that is initiated when said speed signal indicates an engine speed acceleration exceeding a predetermined acceleration, said acceleration sequence is capable of advancing the ignition timing a predetermined number of degrees and maintaining said advancement for a predetermined number of engine revolutions, and is capable of enriching the air-to-fuel ratio of the combustible mixture for a predetermined number of engine revolutions.  
     
     
         11 . A control system as stated in  claim 1 , wherein said independent operating sequence is a come down sequence that is initiated when said speed signal indicates that the engine speed has exceeded a predetermined speed followed by a decrease from said predetermined speed, said come down sequence is capable of advancing or retarding the ignition timing a predetermined number of degrees for a predetermined number of engine revolutions, and is capable of enriching the air-to-fuel ratio of the combustible mixture for a predetermined number of engine revolutions.  
     
     
         12 . A control system as stated in  claim 1 , wherein said independent operating sequence is a recovery bump sequence that is initiated when said speed signal indicates that the engine speed is less than a predetermined speed and is capable of utilizing said speed signal to advance the ignition timing at a first rate and retard the ignition timing at a second rate which is less than said first rate.  
     
     
         13 . A method for controlling the ignition timing of a light duty combustion engine, said method comprising the steps of: 
 (a) receiving an electronic speed signal representative of engine speed,    (b) utilizing said speed signal to select from a plurality of independent operating sequences,    (c) utilizing said selected operating sequence to determine a desired ignition timing value, and    (d) utilizing said desired ignition timing value to provide an electronic ignition signal to an ignition device, wherein said ignition signal affects the ignition timing of the engine.    
     
     
         14 . A method for controlling ignition timing as stated in  claim 13 , wherein one of said plurality of independent operating sequences includes an acceleration sequence that is initiated when said speed signal indicates an engine speed acceleration exceeding a predetermined acceleration and is capable of advancing the ignition timing a predetermined number of degrees and maintaining the timing at said advanced number of degrees for a predetermined number of engine revolutions.  
     
     
         15 . A method for controlling ignition timing as stated in  claim 14 , wherein said ignition signal is representative of the sum of a first timing value and a second timing value that is determined by said acceleration sequence.  
     
     
         16 . A method for controlling ignition timing as stated in  claim 15 , wherein said control system determines said first timing value by utilizing a look up table relating engine speed to said first timing value.  
     
     
         17 . A method for controlling ignition timing as stated in  claim 13 , wherein one of said plurality of independent operating sequences includes a come down sequence that is initiated when said speed signal indicates that the engine speed has exceeded a predetermined speed followed by a decrease from said predetermined speed, and is capable of advancing or retarding the ignition timing a predetermined number of degrees for a predetermined number of engine revolutions.  
     
     
         18 . A method for controlling ignition timing as stated in  claim 17 , wherein said ignition signal is representative of the sum of a first timing value and a second timing value that is determined by said come down sequence.  
     
     
         19 . A method for controlling ignition timing as stated in  claim 18 , wherein said control system determines said first timing value by utilizing a look up table relating engine speed to said first timing value.  
     
     
         20 . A method for controlling ignition timing as stated in  claim 13 , wherein one of said plurality of independent operating sequences includes a recovery bump sequence that is initiated when said speed signal indicates that the engine speed is less than a predetermined speed and is capable of utilizing said speed signal to advance the ignition timing at a first rate and retard the ignition timing at a second rate which is less than said first rate.  
     
     
         21 . A method for controlling ignition timing as stated in  claim 20 , wherein said ignition signal is representative of the sum of a first timing value and a second timing value that is determined by said recovery bump sequence.  
     
     
         22 . A method for controlling ignition timing as stated in  claim 21 , wherein said control system determines said first timing value by utilizing a look up table relating engine speed to said first timing value.  
     
     
         23 . A method for controlling the air-to-fuel ratio of a combustible mixture being provided to a light duty combustion engine, said method comprising the steps of: 
 (a) receiving an electronic speed signal representative of engine speed,    (b) utilizing said speed signal to select from a plurality of independent operating sequences,    (c) utilizing said selected operating sequence to determine a desired air-to-fuel ratio for the combustible mixture, and    (d) utilizing said desired air-to-fuel ratio to provide an electronic air/fuel signal to a valve control device, wherein said air/fuel signal affects the air-to-fuel ratio of the combustible mixture being provided to the engine.    
     
     
         24 . A method for controlling the air-to-fuel ratio as stated in  claim 23 , wherein one of said plurality of independent operating sequences includes an acceleration sequence that is initiated when said speed signal indicates an engine speed acceleration exceeding a predetermined acceleration and is capable of enriching the air-to-fuel ratio of the combustible mixture for a predetermined number of engine revolutions.  
     
     
         25 . A method for controlling the air-to-fuel ratio as stated in  claim 23 , wherein one of said plurality of independent operating sequences includes a come down sequence that is initiated when said speed signal indicates that the engine speed has exceeded a predetermined speed followed by a decrease from said predetermined speed, and is capable of enriching the air-to-fuel ratio of the combustible mixture for a predetermined number of engine revolutions.  
     
     
         26 . A control system for use with a light duty combustion engine, said system comprising: 
 a speed sensor operatively coupled to the engine and having a signal output for providing an electronic speed signal representative of engine speed,    an ignition switch operatively coupled to a capacitive discharge ignition system and having a signal input for receiving an ignition signal capable of affecting the engine ignition timing,    a first air/fuel mixture switch operatively coupled to a solenoid for driving said solenoid in a first direction for enriching a combustible mixture and having a signal input for receiving a first air/fuel signal,    a second air/fuel mixture switch operatively coupled to said solenoid for driving said solenoid in a second direction for enleaning a combustible mixture and having a signal input for receiving a second air/fuel signal, and    an electronic processing device coupled to said speed sensor output for receiving said speed signal, coupled to said ignition switch input for providing said ignition signal, coupled to said first air/fuel mixture switch for providing said first air/fuel signal, and coupled to said second air/fuel mixture switch for providing said second air/fuel signal, wherein said processing device is capable of determining said ignition signal and said first and second air/fuel signals according to an independent operating sequence that is capable of being selected by utilizing said speed signal.