Ignition timing control

• US 5,213,080 A
• Filed: 07/10/1992
• Issued: 05/25/1993
• Est. Priority Date: 07/10/1992
• Status: Expired due to Term

• Current Assignee: Marathon Engine Systems Incorporated
• Original Assignee: Gas Research Institute (GTI Energy)
• Inventors: Bedross, George M., Lambert, John E.
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US07/911,886
• Time in Patent Office: 319 Days
• Field of Search: 123/416, 123/417, 123/418, 123/612, 123/609
• US Class Current: 123/406.65
• CPC Class Codes: F02B 75/16 Engines characterised by number of cylinders, e.g. single-cylinder engines F02B75/26 takes precedence
• CPC Class Codes: F02P 3/0456 using digital techniques
• CPC Class Codes: F02P 5/1502 using one central computing unit
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An electronic control system for an internal combustion gas engine adapted to control the timing pulse for spark ignition in a single cylinder gas engine wherein precise timing of the spark advance throughout a wide range of engine speeds can be achieved whereby efficient burning of a lean air/fuel mixture in the combustion chamber of the engine can be achieved to minimize undesirable exhaust gas emissions and to increase the operating engine efficiency.

Claims

1. An engine ignition control system for controlling the timing of the spark for initiating burning in the combustion chamber of a four stroke cycle, single cylinder, internal combustion engine;

said engine having a cylinder, a piston in said cylinder, a crankshaft connected to said piston, said piston being adapted to reciprocate between a top dead center position and a bottom dead center position;

a speed sensor means for developing periodic sensor voltage timing pulses, the cycle time between timing pulses being an indication of engine crankshaft speed;

means for developing ignition timing pulses, each timing pulse having a leading edge corresponding to a voltage change in a timing voltage pulse and a trailing edge corresponding to an opposite voltage change in a timing voltage pulse;

means for developing a spark voltage including an ignition coil and a source of ignition coil current, said spark voltage occurring at a coil primary current interrupt point;

means for measuring in real-time, cycle time and a timing pulse time for one engine cycle; and

means for computing an optimum delay time from the leading edge of a timing pulse for said one cycle to said interrupt point whereby combustion is initiated at a time in advance of the top dead center position.

2. The combination as set forth in claim 1 wherein said computing means comprise a microcomputer electronics unit having a data storage memory containing ignition advance angle values that are determined by crankshaft speed and engine load, said electronics unit including means for calculating the time measured in crankshaft degrees before the top dead center position of said piston for one engine cycle at which said interrupt point is reached.

3. The combination as set forth in claim 2 wherein said electronics unit comprises means for calculating the time measured in crankshaft degrees between the top dead center position of said piston in one engine cycle to the initiation of said coil current whereby said interrupt point occurs after said coil current is initiated.

4. An ignition timing control system for a spark ignition, four stroke cycle, single cylinder, internal combustion engine having a cylinder, a crankshaft and a reciprocating piston in said cylinder connected to said crankshaft, said piston moving in said cylinder between a top dead center position and a bottom dead center position;

a combustion chamber of variable volume defined in part by said piston and cylinder, a spark ignition means in said combustion chamber, an ignition coil connected to said ignition means;

a primary current circuit defined in part by said coil and means for developing a primary current pulse beginning at a fixed dwell time prior to interruption of said current;

an engine crankshaft speed sensor means for developing periodic voltage pickup pulses in advance of the top dead center position for each engine cycle;

means for developing a timing pulse voltage with a leading edge upon a timing voltage increase for each sensor pulse and for interrupting said timing voltage pulse at a trailing edge upon a timing voltage decrease to a low value in advance of each top dead center position of said piston;

means for measuring the cycle time between corresponding edges of two timing pulses and means for measuring the pulse time between said leading and trailing edges of each timing pulse; and

means for computing a delay time from the leading edge of a timing pulse for one cycle to an ignition point at which said primary current circuit is interrupted at an optimum time in advance of the top dead center piston position of a subsequent cycle.

5. The combination as set forth in claim 4 wherein said computer means comprises a microcomputer electronics unit having a data storage memory containing ignition advance angle values that are determined by crankshaft speed and engine load, said electronics unit including means for calculating the time measured in crankshaft degrees before the top dead center position of said piston for one engine cycle at which said ignition point occurs whereby ignition is begun at a crankshaft position with an advance angle before the top dead center piston position to effect optimum combustion efficiency with reduced combustion exhaust products.

6. An ignition timing control system for a four stroke cycle, single cylinder, internal combustion gas engine having a crankshaft and a reciprocating piston movable between a top dead center position and a bottom dead center position;

a crankshaft speed sensor means for developing periodic sensor voltage pulses extending from a zero reference voltage to a peak voltage and from a peak voltage to said zero reference voltage, means for developing a threshold voltage higher than said reference voltage but less than said peak voltage;

means for developing an ignition timing voltage pulse extending from a leading edge corresponding to a first crankshaft position at which said sensor voltage equals said threshold voltage;

a trailing edge of said timing pulse corresponding to a second crankshaft position at which said sensor voltage equals zero;

means for measuring engine cycle time between corresponding timing pulse edges and means for measuring the width of said timing pulse between said leading and trailing edges;

means for developing a spark voltage including an ignition coil and a source of ignition coil current, said spark voltage occurring at a coil primary current interrupt point;

means for computing a time delay between the leading edge of a timing pulse for one cycle to said interrupt point whereby said spark voltage initiates combustion at a predetermined instant before the top dead center position of said piston is reached.

7. The combination as set forth in claim 6 wherein said computing means comprise a microcomputer electronics unit having a data storage memory containing ignition advance angle values that are determined by crankshaft speed and engine load, said electronics unit including means for calculating the time measured in crankshaft degrees before the top dead center position of said piston for one engine cycle at which said interrupt point is reached.

8. The combination as set forth in claim 6 wherein said means for developing a threshold voltage comprises adaptive circuit means responsive to an increase in the frequency of said sensor voltage pulses for increasing the threshold voltage level at higher engine speeds whereby a reliable reference threshold voltage is developed notwithstanding increased electronic noise characteristics of higher engine speeds.

9. The combination as set forth in claim 8 wherein said adaptive circuit means comprises a voltage peak detector means communicating with said speed sensor means for increasing the magnitude of said threshold voltage as periodic voltage peaks of increasing magnitude are developed by said speed sensor means.