Engine spark timing system with retard means and minimum burn timer

• US 4,106,447 A
• Filed: 04/22/1977
• Issued: 08/15/1978
• Est. Priority Date: 04/22/1977
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: West, Gene A.
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Dolinar, Andrew M.
• Application Number:
  US05/789,801
• Time in Patent Office: 480 Days
• Field of Search: 123/117 R, 123/117 D, 123/148 E, 123/146.5 A
• US Class Current: 123/406.66
• CPC Class Codes: F02P 3/0453 Opening or closing the primary coil circuit with semiconductor devices
• CPC Class Codes: F02P 5/152 dependent on pinking detecting or indicating knocks in internal-combustion engines G01L23/22
• CPC Class Codes: G01L 23/225 circuit arrangements therefor
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In a spark timing system for a spark ignited internal combustion engine, means are provided for generating a series of alternating coil-on and coil-off signals in accordance with crankshaft rotation and one or more engine operating conditions, means are provided for normally passing each coil-on signal immediately to the spark coil to turn on current therethrough and means are provided for passing each coil-off signal to the spark coil to turn off current therethrough with a retard determined in accordance with an additional engine operating condition to generate a spark pulse retarded with respect to the normal spark timing. To ensure a minimum burn time for the spark plugs, means are provided to hold the spark coil in the off condition for a predetermined minimum burn time following each retarded coil-off signal, regardless of the possible appearance of a coil-on signal before the end of this minimum burn time.

Claims

1. A spark timing system for an internal combustion engine having a crankshaft, a plurality of spark plugs, a spark coil adapted to provide spark pulses to the spark plugs in predetermined order as the crankshaft rotates, means for providing an electric current through the spark coil including switch means responsive to a coil-on signal to switch on the electric current and thus cause a buildup of electromagnetic energy in the spark coil and further responsive to a coil-off signal to switch off current in the coil and thus release the built up electromagnetic energy as a spark pulse, the system comprising, in combination:

signal generating means timed to crankshaft rotation, shiftable in phase with respect thereto in accordance with a program based on engine operating conditions and effective to generate a train of alternating coil-on and coil-off signals;

first means responsive to the signal generating means to normally pass the coil-on signals directly to the switch means to switch on current in the spark coil immediately with each coil-on signal;

second means responsive to the signal generating means to pass the coil-off signals to the switch means after a retard varying with at least one additional engine operating condition to turn off current in the coil and generate a spark pulse with each coil-off signal after said retard; and

third means responsive to the second means to prevent the first means from passing the following coil-on signal to the switch means for a constant predetermined time, whereby the spark pulse is ensured a predetermined minimum burn time for good engine combustion, even at high engine speed when the next coil-on signal might occur before the retarded previous spark pulse.

2. A spark timing system for an internal combustion engine having a crankshaft, a plurality of spark plugs, a spark coil adapted to provide spark pulses to the spark plugs in predetermined order as the crankshaft rotates, means for providing an electric current through the spark coil including switch means responsive to a coil-on signal to switch on the electric current and thus cause a buildup of electromagnetic energy in the spark coil and further responsive to a coil-off signal to switch off current in the coil and thus release the built up electromagnetic energy as a spark pulse, the system comprising, in combination:

signal generating means timed to crankshaft rotation, shiftable in phase with respect thereto in accordance with a program based on engine operating conditions and effective to generate a train of alternating coil-on and coil-off signals;

bistable circuit means having output means connected to the spark coil and first input means connected to the signal generating means, the bistable circuit means being normally responsive to a coil-on signal on the first input means to assume a first stable state generating a coil-on signal on the output means to turn on current in the spark coil, the bistable circuit means further having second input means and being responsive to a coil-off signal on the second input means to assume a second stable state generating a coil-off signal on the output means to turn off current in the spark coil, the bistable circuit being responsive, when a coil-on signal is on the first input means and a coil-off signal is simultaneously on the second input means, to the coil-off signal;

retard means connected between the signal generating means and the second input of the bistable circuit means, the retard means being responsive to at least one additional engine operating condition and effective to retard the coil-off signal, and thereby the resulting spark pulse, in accordance with said condition;

one-shot multivibrator means connected between the retard means and the second input of the bistable means, the one-shot multivibrator means being responsive to the retarded coil-off signal from the retard means to generate a coil-off signal pulse having a predetermined time duration for application to the second input of the bistable circuit means, whereby the current in the spark coil is held off for at least said predetermined time duration and therefore a minimum burn time equal to said predetermined time duration is provided for the spark plugs for good engine combustion.

3. The method of providing spark pulses to the spark plugs of a spark-ignited internal combustion engine having a crankshaft and a spark coil, comprising the steps of:

generating alternating coil-on and coil-off signals in time with crankshaft rotation and shifted in phase with respect to the crankshaft according to a program based on one or more engine operating conditions to generate a normal spark timing;

normally initiating electric current conduction in the spark coil immediately with each coil-on signal to cause the buildup of electromagnetic energy in the spark coil;

cutting off electric current conduction in the spark coil with each coil-off signal to release the electromagnetic energy in a spark pulse to one of the spark plugs;

retarding the spark pulse from the corresponding coil-off signal by a crankshaft angle or rotation determined by a program based on at least one additional engine operating condition to retard the spark plug firing from the normal timing; and

preventing the initiation of electric current conduction in the spark coil in response to each coil-on signal during a predetermined time after the initiation of the spark pulse resulting from the previous coil-off signal, whereby each spark pulse is ensured a minimum time duration and each spark plug a minimum burn time equal to said predetermined time for good engine combustion.