Claims
- 1. Ignition system for an internal combustion engine (E) having
- an ignition coil (25);
- a controlled main switch (24) connected in series with the primary (24) of the ignition coil and controlling current flow therethrough;
- means (12) coupled to the engine providing a first signal occurring at the time in advance of the ignition instant, and a second signal subsequent to the first signal and commanding interruption of current flow through the coil to cause an ignition event;
- and means controlling the duration of current flow through the ignition coil in advance of the ignition event to be essentially independent of the speed of the engine, and hence of the repetition rate of said first and second signals,
- comprising, in accordance with the invention,
- a memory (15, 30);
- controlled memory loading means (13; 31, 33) loading the memory in the time interval between said second signal and a subsequent first signal, and accumulating a stored value therein representative of said time duration;
- controlled memory clearing means (17, 30) unloading the memory in the time interval between the occurrence of the first signal and the occurrence of the next subsequent second signal at variable and controlled rates;
- a timing means (18) establishing a timing interval connected to said controlled memory clearing means and controlling the unloading rate during the timing interval thereof to differ from the unloading rate subsequent to said timing interval;
- and means (20, 21; 39) connected to and controlled by said memory (15, 30) and responsive to a predetermined storage or loading state of the memory controlling said main switch (24) to close the circuit through the primary of the ignition coil (25) to store magnetic energy therein in the interval after the memory has reached said predetermined storage state and before the occurrence of the second signal commanding interruption of the current flow through the coil to cause said ignition event.
- 2. Ignition system according to claim 1, wherein the memory clearing or unloading means includes two unloading stages (17, 19; 37, 38) connected to said memory, one of said unloading stages (19; 37) being controlled by said timing means (18) and unloading said memory at a rate which is higher than the unloading rate of the other of said clearing or unloading means (17; 38).
- 3. Ignition system according to claim 2, wherein the ratio of the clearing or unloading rate of the second unloading stage (17, 38) to the loading rate of the controlled memory loading means (13; 31, 33) is greater than the duty ratio of the respective cycles occurring between the first and second signal, and then between the second and subsequent first signal of a signal train having, alternately, first and second signals.
- 4. Ignition systems according to claim 3, wherein the clearing or unloading rate of the second unloading stage (17, 38) is higher than the loading rate by the memory loading means by a percent factor defined by (n).sub.o /(k.multidot.n.sub.o.sup.2),
- wherein (n).sub.o represents acceleration; k the number of cylinders of the engine (E); n.sub.o the speed of the engine (E);
- and wherein said percentage factor forms the largest value of speed and acceleration for the respective engine.
- 5. Ignition system according to claim 1, further including a current limiting circuit (26, 27) connected to the primary coil of the ignition coil (25).
- 6. Ignition system according to claim 3, wherein said discharge stages comprise two parallel connected discharge circuits (17, 19).
- 7. Ignition system according to claim 1, wherein the memory comprises a capacitor;
- said memory loading means comprises a capacitor charge source (13);
- and said memory clearing means comprises two parallel connected capacitor discharge circuits (17, 19), one of said discharge circuits (19) being connected to and controlled by said timing means (18) to provide a discharge path for said capacitor in addition to the discharge path provided by the circuit of the other of said discharge stages (17).
- 8. Ignition system according to claim 1, wherein the memory comprises a digital counter (30);
- said memory loading means, and said controlled memory clearing means, respectively, comprises pulse generator means (33; 37, 38) providing count pulses to said digital counter (30) to enter digital values representative of the time duration upon loading of said memory, and to remove from the then resulting count state of said counter digital values during unloading or clearing of said digital memory.
- 9. Ignition system according to claim 8, wherein said pulse generator means, and forming at least part of the memory clearing means, comprises pulse frequency generator means (37, 38) having, respectively, a higher frequency and a lower frequency, and a logic circuit (34-39) respectively connecting the higher frequency, during said time interval, and under control of said timing means (18) and thereafter the lower frequency to the counter (30).
- 10. Ignition system according to claim 9, wherein said pulse generator means includes a single pulse generator (37) and a frequency divider to generate said frequency having the lower frequency rate.
- 11. Ignition system according to claim 1, including means (14) controlling the timing interval of said timing circuit (18) as a function of an operating parameter of at least one of: the engine; the ignition system.
- 12. Ignition system according to claim 1, further including means (14) connecting the timing means (18) to the source of supply voltage (B+) for said system, to control the timing interval of said timing means as a function of supply voltage of said system.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2703431 |
Jan 1977 |
DEX |
|
Parent Case Info
Cross reference to related applications, assigned to the assignee of the present application:
The present invention relates to an ignition system for internal combustion, and more particularly to an ignition system in which a semiconductor switch controls current flow through the primary of an ignition coil for a period of time just sufficient to store electromagnetic energy in the coil without prolonged current flow therethrough after the energy has been stored.
US Referenced Citations (7)