US3821944A - Igniter for an internal combustion engine - Google Patents

Abstract

An igniter for an internal combustion engine using a semiconductor switch is disclosed. A voltage dropping element is selectively inserted in a feeding circuit of an ignition coil of the engine which is connected to a DC electric source during the time of initiation of the engine or during a normal operation so as to compensate for a battery voltage drop at the time of initiation of the engine. A diode is provided for feeding a base current directly to the semiconductor switch at the time of ignition of the engine by short-circuiting the voltage dropping element at such time. A decrease in the base current of the semiconductor switch at the time of initiation of the engine, due to the voltage dropping element, is thereby avoided. The semiconductor switch is thus sufficiently conducted at the time of initiation of the engine, such that sufficient current is fed to the ignition coil so as to improve the ignition efficiency at the time of initiation of the engine.

Description

United States Patent [191 Miki et a1.

[ IGNITER FOR AN INTERNAL COMBUSTION ENGINE [75] Inventors: Takao Miki, l-limeji; Toshikazu Saita, Takasago, both of Japan [73] Assignee: Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan 22 Filed: Feb. 22, 1972 21 Appl. No.: 227,857

[30] Foreign Application Priority Data Feb. 23, 1971 Japan 46-10838 [52] US. Cl. 123/179 BG, 123/148 E [51] Int. Cl. F02p 3/02 [58] Field of Search 123/148 B179 86; 315/209 T; 290/37, 38

[56] References Cited UNITED STATES PATENTS 3,173,410 3/1965 McLaughlin 123/179 BG 3,180,997 4/1965 Short et a1. 290/38 3,434,463 3/1969 Bartch 123/148 E [451' July 2, 1974 Primary Examiner-Laurence M. Goodridge Attorney, Agent, or FirmOblon, Fisher, Spivak, Mc- Clelland & Maier [57] ABSTRACT An igniter for an internal combustion engine using a semiconductor switch is disclosed. A voltage dropping element is selectively inserted in a feeding circuit of an ignition coil of the engine which is connected to a DC electric source during the time of initiation of the engine or during a normal operation so as to compensate for a battery voltage drop at the time of initiation of the engine. A diode is provided for feeding a base current directly to the semiconductor switch at the time of ignition of the engine by short-circuiting the voltage dropping element at such time. A decrease in the base current of the semiconductor switch at the time of initiation of the engine, due to the voltage I dropping element, is thereby avoided. The semiconductor switch is thus sufficiently conducted at the time of initiation of the engine, such that sufficient current is fed to the ignition coil so as to improve the ignition efficiency at the time of initiation of the engine.

2 Claims, 4 Drawing Figures PATENTEDJUL 2 i974 FIG.

FIG.2

FIG.3

BACKGROUND OF THE INVENTION ,cludes a semiconductor such as a transistor or thyristor having a base circuit 10. An interrupter 11, an exciting coil 12 of an electric source generator for supplying an electric charge, and a starter 13 are also provided.

The operation of the igniter for an internal combustion engine as shown in FIGS. 1 and 2 will now be described. ln FIGS. 1 and 2 it should be understood that the interrupter II is shut and opened to thereby shut and open the semiconductor switch 9 and accordingly interrupt the electric current of the ignition coil 8. When initiation of the engine is desired, the moving element of the keyswitch 1 is connected to the contacts 3 and 4 as is shown in FIG. 2 and accordingly, the starter I3 is actuated. At such time, an electric current is fed through the contact 3 to the ignition coil 8, and to the base circuit through the resistor 7. Electric current is also fed through the resistor 7 to the exciting coil 12. Since the voltage drop across the resistor 7 is high, the electric current in the base circuit 10 is extremely low. As a result of the low current in the base circuit 10, the semiconductors, such as the transistors in the switching circuit 9, cannot completely change to a closed condition. The electric current of the ignition coil 8 will also be of an extremely low value. Because of the above, it becomes impossible to initiate the engine, and the same, thereby, is inoperable.

In the past, in an unsatisfactory attempt to overcome the above problem, the base circuit 10 would be connected between the resistor 7 and the connecting point of the ignition coil 8. Additionally, the value of the resistors connected to the base circuit 10 would be decreased, so as to prevent a low base current caused by the voltage drop in the resistor 7. One problem with decreasing the value of the resistors connected to the base circuit 10 is that the same can be easily burned and thereby, rendered inoperative.

Others have attempted to eliminate the outer resistor 7 entirely, but under such conditions, the inner resistance of the ignition coil 8 is greatly increased.

A problem with increasing the inner resistance of the ignition coil 8 is that an overcurrent will be fed to the base circuit 10 during the operation of the engine, whereby again, the resistors of the base circuit 10 can be burned and ultimately rendered inoperative.

SUMMARY OF THE INVENTION It is an object of this invention to' provide a new and improved unique igniter for an internal combustion engine wherein the igniter uses a semiconductor switch which has a base circuit that can be fed a sufficient current at the time of initiation of the engine.

Briefly, in accordance with thepresent invention, the foregoing and other objects are in one aspect attained by the provision of an igniter for an internal combustion engine which includes a first feeding circuit for feeding electric current through an outer resistor to an ignition coil and a second feeding circuit for feeding electric current from the electric source to the ignition coil without passing through the outer resistor. A semiconductor switch is provided for switching the electric current of the ignition coql and the same includes a base circuit. A moving element is provided for at least connecting the base circuit of the semiconductor switch to the electric source during a normal operation of the engine. Finally, a diode is provided and is connected between the base circuit and a terminal of the ignition coil for feeding the electric current of the second feeding circuit to the base circuit without passing, at the time of initiation of the engine, through the outer resistor.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention will readily be obtained as the same becomes better understood by the accompanying drawings wherein:

FIG. 1 is an electrical schematic diagram showing the operation of a conventional igniter, using a semiconductor switch, during normal operation;

FIG. 2 is an electrical schematic diagram showing the operation of the convention igniter of FIG. 1 during initiation of an engwne;

FIG. 3 is an electrical schematic diagram of one preferred embodiment of the igniter of the present invention; and,

FIG. 4 is an electrical schematic diagram of another preferred embodiment of the igniter of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS base circuit 10 and the connecting point A of the resstor 7 and the ignition coil 8.

When initiation of the engine is desired, electric current is fed from the connecting point A through the diode 14 to the base circuit 10. Accordingly, sufficient base current is fed so as to place the semiconductor switch 9 in a completely closed condition. A large amount of electric current will also be fed to the ignition coil 8 and as such, the engine can be easily initiated.

With the present arrangement, since the base circuit 10'is directly connected to the contact 2, it is unnecessary to decrease the resistance in the circuit. Accordingly, there is no possibility of an accident which could cause burning of the resistors in the base circuit 10. In the embodiment of FIG. 3, it is apparent that the base current is increased by the use of the diode 14. However, since the electric current of the exciting coil 12 is also fed to the diode 14, a diode having a large current capacity is required.

FIG. 4 shows an alternative preferred embodiment of the igniter of this invention wherein another diode 15 is inserted. With the use of a second diode, the electric current rating of the diode 14 can be decreased, whereby the igniter can be even more compact and of a lower cost.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within operation of said engine;

a semiconductor switch for switching the electric current through saidprimary winding, said semiconductor switch including a base circuit connected directly to said power source during the normal operation of said engine;-

diode means connected between said base circuit and said terminal of said primary winding for increasing the conduction of said semiconductor switch during the cranking operation of said engine thereby increasing the voltage at said terminal of said primary winding whereby the current from said power source through said primary winding is increased during said cranking operation of said engine.

2. The igniter for an internal combustwon engine according to claim 1, further comprising a second diode connected directly between said base circuit and said power source during the normal operation of said engine, said second diode connected in parallel with said first diode means and biased so as to feed electric current to said base circuit.

Claims (2)

1. An igniter for an internal combustion engine, which comprises: an electric power source; an ignition coil having a primary winding; a resistor connected between said power source and said primary winding of said ignition coil during the normal operation of said engine; means connecting said power source directly to a terminal of said primary winding during the cranking operation of said engine; a semiconductor switch for switching the electric current through said primary winding, said semiconductor switch including a base circuit connected directly to said power source during the normal operation of said engine; diode means connected between said base circuit and said terminal of said primary winding for increasing the conduction of said semiconductor switch during the cranking operation of said engine thereby increasing the voltage at said terminal of said primary winding whereby the current from said power source through said primary winding is increased during said cranking operation of said engine.

2. The igniter for an internal combustwon engine according to claim 1, further comprising a second diode connected directly between said base circuit and said power source during the normal operation of said engine, said second diode connected in parallel with said first diode means and biased so as to feed electric current to said base circuit.

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