US 3367314 A
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Feb. 6, 1968 YOSHIAKI HIROSAWA ETAL 3,367,314
NONCONTACT IGNITION DEVICE Filed Sept. 8. 1965 United States Patent 3,367,314 NON-CONTACT IGNITION DEVICE Yoshiald Hirosawa, Tokyo, Takaya Senzaki, Yamatomachi, Kita-adachi-gun, Saitarna Prefecture, Japan, assignors to Kahushilri Kaislia Honda Gijutsu Kenkyusho, Saitama Prefecture, Japan, a corporation of Japan Filed Sept. 8, 1965, Ser. No. 485,859
Claims priority, application Japan, Sept. 16, 1964,
3 Claims. (Cl. 123-148) ABSTRACT OF THE DISCLOSURE The invention comprises an electrical ignition system for internal combustion engines wherein an A.C. generator source charges a condenser through half-wave rectifier means and an SCR is switched on to discharge the condenser via the primary ignition coil thereby producing a firing spark. The switching circuit for the SCR comprises a constant voltage diode and a resistor connected in series therewith, the combination being in parallel with the SCR. A connection from the junction of the diode and resistor extends to the gate of the SCR so that when a predetermined voltage level in the half-wave signal is reached, the diode current causes a pulse to the gate for firing the SCR which in turn provides the discharge path for the condenser.
This invention relates to a non-contact ignition device for internal combustion engines, wherein the charging and discharging of condenser, as well as the switching of semiconductor elements are utilized.
More particularly the present invention relates to the type of non-contact ignition device wherein an output current of an A.C. generator, such as a magneto generator, which is rotated synchronously with the internal combustion engine, is rectified to charge a condenser and the charged condenser is discharged by means of a switching circuit comprising a silicon controlled rectifier (which hereinafter is abbreviated to SCR) through a primary coil of the ignition coils so that high voltage or tension induced in a secondary coil may be applied to a plug.
A first object of the present invention is to provide an improved non-contact ignition device of the type referred to above wherein a separate or further generator, synchronized with said first mentioned generator as means for feeding a positive signal current to the gate of the SCR,
is eliminated because the condenser or capacitor is discharged by actuating the SCR switching circuit in synchronism with the rotation of the output shaft of the internal combustion engine.
A second object of the present invention is to provide such a device wherein the time when said signal gate current is supplied, that is, the time for igniting can be easily controlled, which object may be achieved concurrently with said first object.
A third object is to provide such a device wherein the pulse circuit in the condenser charging and discharging type ignition device for accomplishing the foregoing objects may be easily constructed.
Further features and advantages of the present invention will be clear from the following explanation of the invention in detail in connection with the accompanying drawings, in which:
FIG. 1 is a connection diagram of the circuit according to the present invention; and
FIG. 2 shows the operational characteristics of the constant voltage diode according to the present invention,
Patented Feb. 6, 1968 wherein time is represented along the abscissa and voltage along the ordinate.
Referring to an embodiment of this invention as illustrated in the drawings, an alternative-current generator 1, such as a magneto generator, is mechanically connected with the output shaft of an internal combustion engine. A half-wave rectifier 2 is connected to generator 1 for rectifying its A.C. output. A condenser or capacitor 3 is connected in parallel with generator 1. A primary coil 4 and a secondary high tension coil 5 comprises the ignition coils. A semiconductor controlled rectifier 6 (SCR) provides the discharge path for capacitor 3.
The gate G of said SCR 6 is supplied with pulses, so as to discharge the condenser 3 synchronously with rotation of the internal combustion engine, and induce high tension or voltage in the secondary coil 5, in order to ignite a plug 7.
It is well known to use another signal generator rotating synchronously with the generator 1 as means for getting the gate signal. It is, however, uneconomical to provide two generators.
The present invention eliminates, the additional generator and accomplishes the same purpose with a simple circuit construction. A constant voltage diode 8 is electrically connected between an anode A of the SCR 6 and the gate G. When the voltage at the anode reaches at a certain or predetermined level, an ignition gate signal is given to the gate G by Zener current from the constant voltage diode 8 so as to turn on SCR 6. A resistor 9 is connected in series between the constant voltage diode 3 and earth E or the common return line.
The A.C. output from the generator 1 is rectified by the rectifier 2, so that the condenser or capacitor 3 is charged, and simultaneously, equivalent voltages are applied to the anode A of SCR and also to the constant voltage diode 8. When the anode potential V is reached, a predetermined Zener voltage in the constant voltage diode 8 as shown in FIG. 2, causes the Zener current suddenly to flow through the resistor 9. SCR 6 is turned-on by appropriately selecting the current passing through the :gate G by the resulting fall of voltage so as to discharge the charged potential of the condenser 3 through the primary coil 4. When the time t (FIG. 2) has elapsed during the discharge, SCR 6 is turned off. The above-mentioned operation is repeated per each cycle of output current from the generator 1.
In the present invention the ignition is performed synchronously with the rotation of the internal combustion engine. Thus, with increase of r.p.m. of the internal combustion engine, the frequency of out-put current of the generator correspondingly increases which is shown in broken curve V in FIG. 2. It will be clear that the control of ignition time may be easily effected by regulating the resistance value of the resistor 9 and consequently the current passing the gate G is correspondingly controlled so as to adjust the turning-on time of SCR.
In lieu of the constant voltage diode 8, a resistor may be theoretically used. However, due to high power consumption and the difficulty of charging the condenser up to a sufliciently high potential and further as the operation is unstable and the sparking energy is low, and so forth, the use of a resistor replacement for diode 8 is impractical for this purpose.
What is claimed:
1. A non-contact ignition device comprising an A.C. generator including an output circuit, a half-wave rectifier connected in the output circuit of said generator, a primary ignition coil and a silicon controlled rectifier having an anode and a cathode and a gate, the anode-cathode being connected in series with rectifier, a condenser connected between the half-wave rectifier and the primary coil in parallel with said silicon controlled rectifier, a secondary coil coupled to the primary coil for producing a spark upon condenser discharge a constant voltage diode, a resistor connected in series with said diode, and said diode and resistor being connected in parallel with the anode-cathode of the silicon controlled rectifier, and a connection from the junction of the resistor and diode to said gate.
2. An ignition system for an internal combustion engine operative from the engine output shaft comprising, in combination A.C. generator means, means connected to the generator for half-wave rectifying the A.C. output, condenser means connected in parallel with the generator means to be charged by the rectified output, an SCR having an anode and a cathode and a gate, a primary ignition coil, said coil and the anode and cathode of the SCR being connected in series with the rectifying means, secondary ignition coil means for developing a high voltage discharge upon discharge of the condenser means, a switching circuit for the SCR, said circuit comprising a constant voltage diode and a resistor connected in series, and a connection from between the diode and resistor to the gate for supplying a pulse to the gate to turn the SCR References Cited UNITED STATES PATENTS 2,030,228 2/1936 Randolph et a1 123148 2,071,573 2/1937 Randolph et al 123148 2,151,796 3/1939 Peters 123148 2,203,579 6/1940 Randolph 123148 OTHER REFERENCES Solid State Products Incorporation, One Pingres St. Salem, Mass, Bulletin D 420-02, August 1959, pages 17-18 (Figure 27).
Solid State Products Incorporation, Bulletin D 4211-02, September 1960, pages 15 and 16 (Figure 22).
20 LAURENCE M. GOODRIDGE, Primary Examiner.