Breakerless ignition system for a multicylinder internal combustion engine

Abstract

A breakerless ignition system for a multicylinder internal combustion engine comprising solid state switching means to allow a primary current to flow and then be cut off through each of the ignition circuits, an improvement wherein a control circuit is provided which is adapted to control the solid state switching means so as to prevent the primary current from flowing through more than two ignition circuits.

Description

BACKGROUND OF THE INVENTION

A multicylinder internal combustion engine of small size often has a breakerless ignition system employed including a corresponding number of ignition coils to that of the cylinders of the engine without using a distributor in consideration of watertightness of the ignition system. If the ignition system is of a primary current interruption type, it is necessary for the ignition system to have a corresponding number of solid-state switching means to that of the ignition coils for interruption of the primary current through the respective ignition coils, resulting in an increased current consumed when the engine starts to operate or when it operates at low speed. In the case that the engine has two or three cylinders, if the ignition coils corresponding to the respective cylinders each consume 5 to 6 amp. of the primary current therethrough, the engine requires 10 to 18 amp. of the primary current as a whole. Thus, the engine as for a bicycle, which has a battery of relatively lower capacity, unpreferably has great load applied on the battery.

OBJECTS OF THE INVENTION

Accordingly, it is a principal object of the present invention to provide a breakerless ignition system for a multicylinder engine wherein a primary current through the entire ignition system is as small as possible.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a breakerless ignition system for a multicylinder internal combustion engine comprising a plurality of ignition circuits each including an ignition coil and solid state switching means to control said ignition coil so as to allow a primary current to flow through said ignition coil and to be cut off from flowing through said ignition coil and a control circuit to control each of said solid state switching means of said ignition circuits, said control circuit associated with a signal generator rotating in time with said engine for generating signals to operate said control circuit, an improvment wherein said control circuit comprises means to sequentially conduct said solid state switching means for said ignition circuits so that when one of said solid state switching means conducts to allow a primary current to flow through the corresponding ignition coil the remaining solid state switching means are non-conductive, said signal generator including a corresponding number of signal coils to that of said ignition circuits, which control said means to sequentially conduct said solid state switching means.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects and features of the present invention will become apparent from the description of the preferred embodiments of the present invention taken with reference to the accompanying drawing;

FIG. 1 is a schematic diagram showing a breakerless ignition system for a multicylinder engine according to the present invention;

FIG. 1A is illustrative of one of the generating elements of the signal generator shown in FIG. 1 in connection with the rotor thereof;

FIG. 2 shows output signals from a signal circuit and primary currents through ignition coil;

FIG. 3 is a schematic diagram showing another embodiment of the present invention with a signal generator omitted for simplification;

and FIG. 4 is a fragmentary schematic diagram showing further embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 of the accompanying drawing, there is shown a breakerless ignition system 1 of the present invention for a three cylinder internal combustion engine which comprises three ignition coils 10, 12 and 14 for respective cylinders of the engine. The ignition coils 10, 12 and 14 have primary coil portions 20, 22 and 24 at one ends commonly connected to one end of a resistance 2 to the other end of which is connected a power source not shown in FIG. 1 and secondary coil portions 30, 32 and 34 connected to respective ignition plugs 40, 42 and 44. The primary coil portions 20, 22 and 24 have the other ends connected to solid state switching circuit 50, 52 and 54 which are shown to comprise typically NPN type transistors which are in turn grounded. The ignition coil 10 and the solid state switching means 50 constitute an ignition circuit 60 for one of the cylinders, and similarly the ignition coils 12 and 14 and the solid state switching means 52 and 54 constitute ignition circuits 62 and 64 for the remaining cylinder, respectively.

The solid state switching means or transistors 50, 52 and 54 have the respective control electrodes or bases 50a, 52a and 54a connected to a control circuit 7 which may comprise three flip-flop circuits 70, 72 and 74 associated with the respective transistors 50, 52 and 54. The flip-flop circuits 70, 72 and 74 which are of conventional reset-set type, each include S- and R-input terminals and Q- and Q-output terminals with the Q-terminals of the flip-flop circuits 70, 72 and 74 connected to the respective bases of the transistors 50, 52 and 54. As understood by those skilled in the art, each of such flip-flop circuits is adapted to generate a positive voltage at the Q-terminal and a zero voltage at the Q-terminal when a signal is applied at the S-terminal and to generate a zero voltage at the Q-terminal and a positive voltage at the Q-terminal when a signal is applied at the R-terminal. Thus, when a signal is applied at the S-terminal of the flip-flop circuit 70, for example, it has the output voltage applied at the base of the transistor 50 so that the primary current flows from the power source E through the ignition coil 10 and then through the transistor 50, with the result that the energy is accumulated by the primary coil portion 20. Thereafter, when a signal is applied at the R-terminal of the flip-flop circuit 70, it has a zero voltage generated at the Q-terminal thereof so that the transistor 50 becomes non-conductibe to thereby interrupt the primary current through the ignition coil 10, with the result that a high voltage is established across the secondary coil portion 30 of the ignition coil 10 so that the corresponding ignition plug 40 is sparked for ignition of the cylinder in which the plug 40 is contained. The flip-flop circuits 72 and 74 operate the associated ignition circuits 62 and 64 in a similar manner.

A signal generator 8 is provided which may comprise an inductor type rotor 89 having a pole 86a integral with the rotor 86 and a stator including three generating elements 80, 82 and 84 angularly spaced by the equal distance adjacent to the periphery of the rotor. One of the generating elements 80 is particularly illustrated in FIG. 1A, which may comprise an eternal magnet 81 magnetised as shown two core pieces 83 and 83' mounted on the magnet at both ends thereof with the axes of the core pieces 83 and 83' normal to the axis of the magnet and a signal coil 85 wound around one of the core pieces 83. The core pieces are so shaped that when the rotor pole 86a of the rotor 86 faces them, they are equally spaced from the rotor pole. The rotor is so connected to a crank shaft 88 of the engine that the former rotates in time with the engine (FIG. 1). Thus, when the rotor of the generator 8 rotates in a direction indicated by an arrow of FIG. 1 one complete revolution, the generating element 80 first generates a signal, then the generating element 82 and last the generating element 84 generate signals, respectively. The signal generator 8 may be alternatively of any other type which can generate signals in synchronism with the revolution of the engine. It will be understood that the signal generator may be disposed in a magneto constituting the power source E so that the magnetic filed of the magneto can be also employed commonly for the signal generator. The signal coils of the generating elements 80, 82 and 84 have the respective outputs connected to inputs of respective amplifying and wave-modifying circuits 90, 92 and 94 which may be of any suitable type. The amplifying and wave-modifying circuit 90 has the output connected both to the R-terminal of the flip-flop circuit 70 and to the S-terminal of the flip-flop circuit 72. Similarly, the amplifying and wave-modifying circuit 92 has the output connected both to the R-terminal of the flip-flop circuit 72 and to the S-terminal of the flip-flop coicuit 74 and the amplifying and wave-modifying circuit 94 has the output connected both to the R-terminal of the flip-flop circuit 74 and to the S-terminal of the flip-flop circuit 70.

In operation, upon rotation of the rotor 86 of the signal generator 8 in the direction indicated by the arrow in FIG. 1, the voltage generated by the signal coil in the generating element 80 is applied to the amplifying and wave-modifying circuit 90 which in turn outputs the voltage having the wave-form as shown in FIG. 3A. Such output voltage from the circuit 90 is applied to the R-terminal of the flip-flop circuit 70 and therefore, the Q-terminal of the flip-flop circuit 70 supplies no voltage to the base of the transistor 50. Thus, the primary current as shown in FIG. 2D flowing through the ignition coil 10 is then cut off whereby the ignition coil 10 establishes a high voltage across the secondary coil portion 30 so that the plug 40 can be sparked for ignition of the cylinder in which the plug 40 is contained. Meantime, the output voltage from the amplifying and wave-modifying circuit 90 is also applied to the S-terminal of the flip-flop circuit 72 and therefore, the Q-terminal of the flip-flop circuit 72 has the output voltage applied to the base of the transistor 52. Thus, the transistor 52 becomes so conductive that the primary current starts to flow through the primary coil portion 22 of the ignition coil 12 and through the transistor 52 as shown in FIG. 2E. At that time, since the generating elements 82 and 84 have no signals generated therefrom the remaining transistors 74 and 70 remain still non-conductive to thereby flow no primary current therethrough.

When the rotor 86 of the signal generator 8 continues to rotate until it faces the generating element 82, then the latter generates a signal to apply it to the amplifying and wave-modifying circuit 92 which in turn generates the output voltage as shown in FIG. 2B. The output voltage from the amplifying and wave-modifying circuit 92 is applied to the R-terminal of the flip-flop circuit 72 and therefore, the Q-terminal of the flip-flop circuit 72 applies no voltage to the base of the transistor 52. Thus, the primary current as shown in FIG. 2E flowing through the ignition coil 12 is then cut off whereby the ignition coil establishes a high voltage across the secondary coil portion 32 so that the plug 42 can be sparked for ignition of the cylinder in which the plug 42 is contained. Meantime, the output voltage from the amplifying and wave-modifying circuit 92 is also applied to the S-terminal of the flip-flop circuit 74 and therefore, the Q-terminal of the flip-flop circuit 74 has the output voltage applied to the base of the transistor 54. Thus, the transistor 54 becomes so conductive that the primary current starts to flow through the primary coil portion 24 of the ignition coil 14 and through the transistor 54 as shown in FIG. 2F. When the rotor 86 of the signal generator 8 continues to rotate until the pole 86a faces the generating element 84, then the signal coil in the generating element 84 generates a signal which is applied to the amplifying and wave-modifying circuit 94 to thereby output the voltage as shown in FIG. 2C therefrom. The output from the circuit 94 causes the flip-flop circuit 74 to operate the transistor 54 to cut off the primary current through the primary coil portion 24 of the ignition coil 14 which establishes a high voltage across the secondary coil portion 34 of the ignition coil 14 for ignition of the cylinder in which the plug 44 is contained, just as described in connection with the operation of the flip-flop circuits 70 and 72. Also, the output voltage from the circuit 94 causes the flip-flop circuit 70 to operate the transistor 50 to allow the primary current as shown in FIG. 2F to flow through the primary coil portion of the ignition coil 10 for preparation for the next operation thereof. As understood from FIGS. 2D to 2F, the primary currents through the ignition coils 10 to 14 never flow at the same time, with the result that the entire consumed current by the ignition system 1 can be considerably decreased. It will be also understood that the resistance 2 can be commonly employed for all of the ignition coils 10 to 14 because the primary current flows through any one of the ignition coils.

FIG. 3 shows another embodiment of the breakerless ignition system 100 for three cylinder engine in accordance with the present invention, wherein the same numerals designate the same components as those of FIG. 1. The ignition system 100 of FIG. 2 is substantially similar to that of FIG. 1, except that the outputs of the amplifying and wave-modifying circuits 90, 92 and 94 are connected only to the R-terminals of the respective flip-flop circuits 70, 72 and 74 with the Q-terminals connected to the S-terminals of the respective flip-flop circuits 72, 74 and 70. With this arrangement, when the amplifying and wave-modifying circuit 90 outputs the voltage, the flip-flop circuit 70 operates the transistor 50 to conduct so that the primary current starts to flow the ignition coil 10 and provide the output voltage at the Q-terminal of the flip-flop circuit to apply it to the S-terminal of the adjacent flip-flop circuit 72 which in turn controls the transistor 52 to cut off the primary current flowing through the ignition coil whereby a high voltage is established across the secondary coil portion 32 so that the plug 42 is sparked in the corresponding cylinder. It will be understood that the remaining flip-flop circuits 72 and 74 operate in the same manner as described in connection with the flip-flop circuit 70.

FIG. 4 shows an embodiment of a breakerless ignition system 200 adapted to ignite a two cylinder internal combustion engine and which comprises two ignition circuits 60 and 62 including ignition coils 10 and 12, NPN type transistors 50 and 52, a resistance 2 and a power source E (not shown) which are arranged in a substantially similar manner as those of the ignition systems 1 and 100 of FIGS. 1 and 3. The ignition system 200 also comprises a set-reset type flip-flop circuit 70 with the Q-terminal connected to the base of the transistor 50 and with the Q-terminal connected to the base of the transistor 52. The flip-flop circuit 70 has the S-terminal connected to the output of amplifying and wave-modifying circuit 90 and the R-terminal connected to the output of the amplifying and wave-modifying circuit 92. When the amplifying and wave-modifying circuit 90 applies an output voltage to the S-terminal of the flip-flop circuit 70 which at the Q-terminal then applies the output voltage to the base of the transistor 50 to conduct it so that the primary current starts to flow through the primary coil portion of the ignition coil 10 and which at the Q-terminal stops applying the voltage to the base of the transistor 52 to cut off the primary current through the ignition coil 12 so that the ignition coil 12 establishes a high voltage across the secondary coil portion of the ignition coil 12 to thereby spark the plug 42 for ignition of the corresponding cylinder. Next, the amplifying and wave-modifying circuit 92 outputs the voltage which operates the flip-flop circuit 70 to control the transistor 50 to cut off the primary current through the ignition coil 10 and the transistor 52 to allow the primary current to flow through the ignition coil 12. Thus, the plug 40 is sparked so that the corresponding cylinder is ignited.

It will be understood that the ignition system 100 of FIG. 3 has the signal generator (not shown) including three signal generating elements connected to the amplifying and wave-modifying circuits 90 to 94, respectively and similarly the ignition system 200 of FIG. 4 has the signal generator also (not shown) including two signal generating elements connected to the amplifying and wave-modifying circuits 90 and 92, respectively.

Although some preferred embodiments of the present invention have been described with reference to the accompanying drawings, they are for the purpose of illustration and not intended to define the present invention. It will be understood that various changes and modifications in arrangement and construction might be made without departing from the spirit and scope of the present invention. For example, it will be understood that the present invention can be also applied to a breakerless ignition system for a four or six cylinder internal combustion engine in a similar manner. The present invention should be defined only by the appended claims.

Claims

What is claimed is:

1. A breakless ignition system for a multicylinder internal combustion engine comprising a plurality of ignition circuits each including an ignition coil and solid state switching means to control said ignition coil so as to allow a primary current to flow through said ignition coil and to cut off said primary current so that a high voltage is established across said ignition coil and a control circuit to control each of said solid state switching means of said ignition circuits, said control circuit associated with a signal generator rotating in time with a multicylinder internal combustion engine for generating signals to operate said control circuit, the improvement wherein said control circuit comprises a corresponding number of flip-flop circuits to that of said ignition circuits, said flip-flop circuits each having one of the output terminals connected to the control terminal of the corresponding solid state switching means so that it interrupts said solid state switching means with one of the adjacent flip-flop circuits signaling the other flip-flop circuit to cause conduction of the corresponding solid state switching means with said other flip-flop circuit when said one flip-flop circuit interrupts the corresponding solid state switching means, said signal generator including a corresponding number of signal coils to that of said ignition circuits, which control said flip-flop circuits.

2. A breakerless ignition system as set forth in claim 1, wherein each of said signal coils of said signal generator is connected to the corresponding one of said flip-flop circuits at one of the input terminals and also to the adjacent flip-flop circuit at the other input terminal.

3. A breakerless ignition system as set forth in claim 1, wherein said flip-flop circuits each has one of the output terminals connected to the control terminal of the corresponding solid state switching means and the other output terminal connected to one of the input terminals of the adjacent flip-flop circuit and wherein each of said signal coils of said signal generator is connected to the corresponding one of said flip-flop circuits at the other input terminal.

4. A breakerless ignition system for a two cylinder internal combustion engine comprising two ignition circuits each including an ignition coil and a solid state switching means to control said corresponding ignition coil so as to allow a primary current to flow through said corresponding ignition coil and to cut off said primary current so that a high voltage is established across said ignition coil and a control circuit to control each of said solid state switching means of said ignition circuits, said control circuit associated with a signal generator rotating in synchronism with a two cylinder internal combustion engine for generating signals to operate said control circuit, the improvement wherein said control circuit comprises a single flip-flop circuit having one of the output terminals connected to the control terminal of one of said solid state switching means and the other output terminal connected to the other solid state switching means so that when said flip-flop circuit interrupts one of said solid state switching means it causes conduction of the other solid state switching means, said signal generator including two signal coils connected to the input terminals of said flip-flop circuit, respectively.