US3361123A - Contact-less ignition system - Google Patents

Description

Jan. 2; 1968 RYOJI KASAMA ETAL 3,36

CONTACT-LESS IGNITION SYSTEM Filed Aug. 26, 1965' 3 Sheets-Sheet 1 2 F762 *5. F/G3 F/(i 4 F/G 5 F/6T6 F/G 7 3 6 mp1 5 a ,4 a 5 4' 5 INVENTORS 03i Kasa Sai Suda.

ATTORNEY Jan. 2; 1968 RYOJI KASAMA ETAL 3,

CONTACT-LESS IGNITION SYSTEM Filed Aug. 26, 1965 3 Sheets-Sheet 2 v 56 34 58 C 56 C C 570) .i 560 566' INVENTOR5 R3035 Kesama, 613i Sudcs.

ATTORNEY Jan. 2, 1968 mo. KASAMA ETAL 3,3 3

CONTACT-LESS IGNITION SYSTEM 3 Sheets-Sheet Filed Aug. 26, 1965 Ang/e 0f rofaf/bn INVENTORS R c M 5&3! 3

PCLMKQ, an.

ATTORNEY United States Patent 3,361,123 CONTACT-LESS IGNITION SYSTEM Ryoji Kasama and Seiji Suda, Hitachi-shi, Japan, assigmors to Hitachi, Ltd., Tokyo, Japan Filed Aug. 26, 1965, Ser. No. 482,768 Claims priority, application Japan, Aug. 28, 1964, 39/ 48,416 4 Claims. (Cl. 123-148) ABSTRACT OF THE DISCLOSURE This invention relates to a contact-less ignition apparatus for the ignition coil of an internal combustion engine and comprises an ignition point detecting device formed of a U-shaped supporting member of insulating material. First and second air coupled coils are secured to opposite inner surfaces of the supporting member and are electromagnetically coupled to each other only through a relatively large air gap. A high frequency source of oscillations is connected to one of the coils and a pulse shaping circuit is connected to the remaining coil. A rotary screening member driven by the engine is interposed between the first and second coupling coils for periodically screening between the coils and substantially reducing the high frequency energy transmitted from the first coupling coil to the second coupling coil by means of absorption of the high frequency energy in the rotary screening member.

The present invention relates to contact-less ignition systems.

With the rate of revolution of engines for automobiles becoming increasingly higher these days, the ignition systems of the type wherein the primary current of an ignition coil is interrupted by the action of the contact of a contact breaker are being replaced progressively by ignition systems of the contact-less type using transistors. In such contact-less ignition systems, a small-sized A.C. generator or phototransistor, which is adapted to operate in association with the rotation of an engine, is used for detecting the ignition point, and the primary current of an ignition coil is current interrupted by interrupting transistors connected to the ignition coil. Proper timing of the point of interruption is achieved by means of the output of said generator or phototransistor.

Ignition systems using a small-sized A.C. generator, however, have the drawback that the output of the generator is not stabilized until the rate of revolution of the engine rises to a certain level, because such systems are operated utilizing an electromotive force e, that is proportional to and the value of d s dt increases in proportion to the rate of revolution of the rotor of the generator. Furthermore, the waveform of the output varies greatly between the operations at a low speed and at a high speed, therefore when the rate of revolution of the generator is low, the output voltage thereof is extremely low, making it ditficult to use for the detection of the ignition point. In addition to the above, the phase of the output current drawn from the generator lags with respect to that of the output voltage generated in the generator, because the generator comprises an inductive component. Such a lag in phase becomes progressively greater with increasing frequency of the current generated, which in turn will cause delay in ignition time of the ignition system, and thus makes the detection and adjustment of the ignition point diflicult.

Turning now to the ignition system wherein a phototransistor is used as means for detecting the ignition point, while it is possible to obtain a substantially constant output with respect to the ignition point of engine, independently of the number of rotations and hence of engine speed, there is the drawback that, when the ignition system is used for automobiles, it is virtually impossible to obtain a long lasting light source whose intensity does not vary greatly with age, which is required for properly controlling the phototransistor.

The present invention has been achieved with a view to obviating the foregoing drawbacks, and an object of the present invention, therefore, is to provide an ignition systern wherein a constant interrupted current is supplied to an ignition coil, independently of the rpm. of engines. This is achieved in the present invention by introducing the output from means for generating high frequency current independently of the rate of rotation of the engine to a first coupling coil for controlling the inductive voltage of a second coupling coil. The second coupling coil is dis posed opposite to said first coupling coil, and its output is controlled by means of a rotary plate adapted to operate in association with the rotation of the engine and to cross the interspace between said first and second coupling coils at a predetermined interval of angle of rotation. The form of the signal voltage of the second coil then is shaped into a pulse wave through a waveform shaping circuit, and amplified to control the primary current of the ignition coil.

Another object of the present invention is to provide an ignition system which com-prises an ignition point detecting device having a first coupling coil connected to the output end of means for generating high frequency current and a second coupling coil disposed opposite to said first coupling coil with a rotary plate intervening therebetween. The rotary plate is adapted to rotate in association with the rotation of engine and the second coupling coil is connected to a waveform shaping circuit, and a constant voltage source, the output-voltage thereof being altered according to the rpm. of the engine. This ar rangement is connected to the terminal of a power source whereby change in the inductive voltage of said second coupling coil is controlled in accordance with the increase in rate of revolution of the engine, thus advancing the ignition point automatically.

A still further object of the present invention is to provide an ignition system comprising an ignition point detecting device having a first coupling coil connected to the output end of means for generating high frequency current and a second coupling coil disposed opposite to said first coupling coil with a rotary plate intervening therebetween. The rotary plate is adapted to rotate in association with the rotation of the engine and the inductive voltage of the second coupling coil is introduced to an ignition coil through a waveform shaping circuit and an amplifying circuit. In this arrangement the width of the rotary plate is varied to adjust the voltage generated in said second coupling coil, whereby the angle of flowing the primary current through the primary winding of said ignition coil is controlled.

The present invention will be illustrated in further detail hereinafter by way of an embodiment shown in the drawings, in which FIG. 1 is a block diagram of an ignition point detecting device;

FIGS. 2 through 4 show waveforms at various portions of the ignition point detecting device;

FIG. 5 is a front elevational view of said detecting device;

FIG. 6 is a plan view of the same;

FIG. 7 is a plan view of a rotary plate as rotated at 45 degrees;

FIG. 8 is a characteristic chart illustrating the change in signal voltage of the ignition point detecting device of FIG. 4;

FIG. 9 is a plan view of a modification in shape of the rotary plate;

FIG. 10 is another block diagram showing an embodiment of the present invention;

FIG. 11 is the electrical connection drawing of the device of FIG. 10;

FIG. 12 is the electrical connection drawing of another embodiment of the constant voltage source shown in FIG. 11; and

FIG. 13 shows voltage waveforms at various portions of the circuit shown in FIGURE 12.

Referring to FIG. 1, reference numeral 1 indicates an ignition point detecting device which comprises high frequency generating means 2 having a constant frequency and a constant amplitude independently of the rotation of the engine, a first coupling coil 3 connected to the output end of said high frequency generating means 2 and a second coupling coil 4. The voltage induced in said second coupling coil 4 is amplified in a suitable amplifier of conventional construction and used as an output signal.

The coupling coils 3 and 4, as shown in FIGS. 5 to 7, are mounted on an insulating member 5 in opposed relation to each other, and a rotary plate 6 is disposed between said coils so as to cross the interspace between the coils at a predetermined time interval.

As shown in FIGURE the output of such an ignition point detecting device 1 is connected to a waveform shaping circuit '7 which is energized in common with device 1 from a constant voltage source means 8. The output from wave shaping circuit 7 is amplified through an amplifying circuit 9 and connected to the primary coil of an ignition coil 10.

The waveform shaping circuit 7 serves to shape the form of output signal of the detecting device 1 into a rectangular waveform or a pulse waveform having a short rise and fall time, and is composed of Schmitt trigger circuit or a monostable multivibrator circuit.

The constant voltage source means 8 serves to maintain the voltage applied to ,said waveform shaping circuit 7 and the ignition point detecting device 1 constant.

The amplifying circuit 9 amplifies the output of the waveform shaping circuit 7 to introduce it into the ignition coil 10 and is composed of a DO. amplifying circuit or an amplifying circuit of the condenser-discharge type wherein a voltage raised by a D.C.-D.C. converter is led into a condenser to charge the same and the electric charge thereof is utilized.

The present invention having such a construction as described above will be further explained with reference to the electrical connection diagram shown in FIG. 11.

Reference numeral 1 indicates the ignition point detecting device comprising the high frequency generating means 2 having the first coupling coil 3, and the second coupling coil 4. The first coupling coil 3 of the high frequency generating device 2 has its one end connected to a terminal A of a battery or power source 12 through the collector 38c-emitter 382 of a transistor 38 and the other end to a terminal B of the power source through a collector 13cemitter 136 of a transistor 13 and a resistor 14. A resistor 15 and a condenser 16 arranged in parallel thereto are connected between a base 13b of transistor 13 and one end of the coupling coil 3. Furthermore, between the emitter 13e-collector 130 there is connected a condenser 17. A resistor 18 having its one end connected to the terminal B of the power source is connected to said resistor 15 in series. A condenser 19 has one end connected to the emitter 13s, with the other end connected to one end of the coupling coil 3.

One end of the second coupling coil 4, arranged opposite to said first coupling coil 3 is connected to a base 2% of a transistor 23, with the other end connected to the terminal B of the power source through a resistor 21 and a condenser 22 arranged in parallel thereto. An emitter 20a of the transistor 20 is connected to the terminal B of the power source, while a collector 290 of the same is connected to the terminal A of the power source through a resistor 23, a condenser 24 and the collector 38cemitter 382 of the transistor 38.

Reference numeral 7 indicates the wave form shaping circuit for shaping the waveform of induced voltage in the coupling coil 4 into a pulse waveform, said shaping circuit comprising transistors 25 and 26 having respective emitters 25c and 26e connected to the terminal B of the power source through a common resistor 27. A base 25b of the transistor 25 is connected to the collector 200 of transistor 2t of said ignition point detecting device 1 through a resistor 28, while a collector 250 is connected to the terminal A of the power source through a resistor 29 and the collector 38c-emitter 38a of the transistor 38. On the other hand, a base 26b of the other transistor 26 is connected to the collector 250 of said transistor 25 through a resistor 30 and a condenser 31, and at the same time it is connected to the terminal B of the power source through a resistor 32, and a collector 260 is connected to the terminal A of the power source through a resistor 33 and the collector 38c--ernitter 38c of the transistor 38.

The constant voltage source means 8 has a resistor 34 which is connected between the collector 380 of the transistor 33 and the terminal B of the power source. An emitter 36c of a transistor 36, whose base 36b is connected to an intermediate terminal of the resistance 34, is connected to the collector 380 of transistor 38, whose emitter 38c-collector 380 are connected in series to the power source, through a Zener diode 37. The emitter 36@ of the transistor 36 also is connected to the terminal B of the power source through a resistor 39, while the collector 36c of the transistor 36 is connected to the base 381) of the transistor 38.

Reference numeral 9 is the amplifying circuit which comprises a Zener diode 39 having one end connected to the output terminal of said waveform shaping circuit 7, i.e., to the collector 260 of transistor 26 and with the other end connected to a base 41b of a first transistor 41 through a resistor 40. The collector 410 of the transistor 41 is connected to the terminal A of the power source through a resistor 42. Reference numeral 43 indicates a transistor 43 of the second stage, whose base 43b is connected to the emitter 41a of transistor 41 of the previous stage and at the same time connected to the terminal B of the power source through a resistor 44. The collector 43c of transistor 43 is connected to the terminal A of the power source through a resistor 45. A transistor 45 which is connected in series to the primary coil 11 of an ignition coil 10, has its base 461; connected to emitter 43a of transistor 43 of the previous stage and to the terminal B of the power source through a resistor 47, while its collector 46c is connected to the terminal A of the power source through primary coil 11 and a resistor 48. A secondary coil 49 of the ignition coil 10 is connected at one end to the primary coil 11 and at the other end to the terminal B of the power source through an ignition plug Stl.

In one embodiment of the system of the present invention having such a construction as described above, a high frequency current having a constant amplitude as shown in FIG. 2 is introduced into the first coupling coil 3 which is coupled to the second coupling coil through only an air path. First coil 3 is connected to the output end of the high frequency generating means 2 of the ignition point detecting device 1 and the voltage induced in the second coupling coil 4 by the high frequency electromagnetic energy of the first coupling coil 3 is amplified for use as an output signal. The coupling coils 3 and 4 are mounted on the member 5 of insulating material in opposed relation to each other and the rotary plate 6 is provided between these coils, which crosses the interspace between said coils at a constant interval of angle of rotation so as to screen the high frequency electromagnetic energy of the first coupling coil 3, as shown in FIGS. 5 through 7. Hence, when the rotary plate 6 is in the position shown in FIG. 7, a constant induced voltage as determined by the shape and position of the coupling coils 3 and 4 is induced in the second coupling coil 4. Next, when the rotary plate 6 comes to the position as shown in FIG. 6 relative to the coupling coils 3 and 4, the high frequency electromagnetic energy of the coupling coil 3 is attenuated or disappears by being screened by the rotary plate 6 and thus the induced voltage of the second coupling coil 4 is reduced.

This disappearance or attenuation of the high frequency energy is not due to any shunt effect of the rotary plate 6 but due to absorption of the high frequency energy in the rotary plate 6. This can be better understood from an examination of FIG. 5 through FIG. 7. When a part of the rotary plate 6 which is of conductive material is interposed between the coupling coils 3 and 4, eddy currents are produced therein that produce magnetic fluxes that counteract the high frequency magnetic energy of coil 3. Consequently, transmission of the high frequency energy to coil 4 is screened or interrupted and there ap pears an output signal in the second coupling coil 4 as shown in FIG. 3.

In this case, the magnitude of the induced voltage of the coupling coil 4 is not in proportion to the rpm. of the engine, as in the case of the A.C. generator, but it is determined by the oscillation frequency of the high frequency generating means 2. Furthermore, since the oscillation frequency is so high and constant that the maximum amplitude of said induced voltage is not influenced by the rate of the rotation of rotary plate 6, it is possible to make the voltage a modulated amplitude as shown in FIG. 3. Therefore, the signal voltage as shown in FIG. 4 can be obtained by detecting and amplifying the induced voltage. This signal voltage is led into the waveform shaping circuit 7, comprising the transistors 25 and 26, to convertthe same into a rectangular pulse signal, whereby the'trans'istors '41 and 43 in the amplifying circuit 9 as well as the transistor 46 connected in series to the primary coil 11 of the ignition coil 10 are controlled to interrupt the collector current of the transistor 46 and to interrupt the primary current in the ignition coil 10, and a high voltage thus induced in the secondary winding is fed to the ignition plug 50 to cause a spark discharge.

According to the contact-less ignition system as has been described hereinbefore, a high frequency electromagnetic energy is caused to be transmitted from the coil 3 to the coil 4 opposing each other in the ignition point detecting device and a signal voltage is obtained by screening the transmission of high frequency electromagnetic energy by the rotary plate which crosses the interspace between said coupling coils at a predetermined time interval. There are advantages, therefore, that the ignition time is not substantially retarded and that, since the induced voltage generated in the second coupling coil 4 always produces a constant magnitude voltage without being influenced by the rate of rotation of the rotary plate 6, the ignition of an engine can be effected in a stabilized manner.

It is also possible, by the use of a constant voltage source, shown in FIG. 12, in place of the constant voltage source 8, shown in FIG. 11, to advance the ignition time electrically in accordance with the rpm. of the engine. This is achieved by connecting terminals a, b and c to the terminals a, b and c in FIG. 11 respectively, while connecting d, e and f to d, e and 1 respectively, whereupon an emitter 51a of a transistor 51 is connected to the collector 38c of the transistor 38, a collector 51c to the terminal B of the power source through a resistor 52, and a base 51b is connected to the collector 26c of transistor 26, which constitutes the output end of the waveform shaping circuit 7, through a resistor 53 and also connected to a diode 54. The diode 54 has one end connected to the output end of the waveform shaping circuit 7, with the other end connected to the terminal B of the power source through a variable resistor 55 and a base 56b-emitter 56e of a transistor 56. Reference numeral 57 indicates a transistor whose base 57b is connected to the collector 510 of transistor 51 through a resistor 58, while its emitter 57e is connected to the terminal B of the power source and a collector 570 to the cathode of the diode 54 through a resistor 59. A condenser 60 is connected between the emitter 57a of said transistor 57 and the cathode of diode 54. A collector 56c of the transistor 56 is connected to the terminal A of the power source through a resistor 61 and the transistor 38 and also to a base 63b of a transistor 63 through a variable resistor 62. Between an emitter 63c and a collector 63c of the transistor 63, there is connected a Zener diode 37. A resistor 34, connected between the terminal B of the power source and the collector 380 of the transistor 38 has the base 36b of transistor 36 connected thereto at the intermediate terminal 35. The transistor 36 has its emitter 362 connected to the collector 38a of transistor 38 through said Zener diode 37, and also to the terminal B of the power source through the resistor 39. The collector 360 of the transistor 36 is connected to the base 38b of said transistor 38, and the output end of the waveform shaping circuit 7 is connected directly to the terminal e to which the amplifying circuit 9 is connected.

In the system of the present invention above described, the output end of the waveform shaping circuit 7 is connected to the transistor 51 and diode 54. The transistor 51, when the primary current of ignition coil 10 is interrupted, serves to short both ends of the condenser 60 with the transistor 57 and to convert the polarity of the output wave of waveform shaping circuit 7, providing for the next charging period.

The output of waveform shaping circuit 7 charges the condenser 60 through the diode, instantaneously as a current begins to flow in the primary coil 11 of the ignition coil 10. As the terminal voltage of the condenser 6t! rises and the transistor 56 is rendered. conductive with an elevated base electric potential, a voltage drop occurs at the resistor 61 to permit a base current of the transistor 63 to flow through the variable resistor 62, thereby rendering transistor 63 conductive. This means that the zener diode 37, which is used as a reference voltage source for the constant voltage source means 8, is shortened, and as a result, the electric potential of the emitter 36c of transistor 36 is elevated, with the collector current, i.e. the base current of the transistor 38, decreasing, which results in a greater internal resistance and greater voltage drop in the transistor 38.

The pulse duration of output waveform of the waveform shaping circuit 7 varies in accordance with the rpm. of engine, and is represented by change in electric charge in the condenser 60 or change in terminal voltage of the condenser 60. With the terminal voltage of condenser 60 fully saturated, a minimum voltage required for the operation of the point detecting device is set by the output voltage of the constant voltage source means 8. When the number of revolutions becomes high, the pulse duration of the output wave of waveform shaping circuit 7 becomes small, the terminal voltage of condenser 60 is lowered, the internal resistance of transistor 63 is increased, the electric potential of the emitter 36a of transistor 36 is lowered, the collector current is increased and the internal resistance of transistor 38 is reduced, and consequently the output voltage of the constant voltage source means 8 becomes high.

Hence, the output waveform of the point detecting device 1 varies as shown in FIG. 8 and such variation is demonstrated as an advance in the ignition time. Namely, as shown in FIG. 13, when the r.p.m. of engine increases from 11 to I1 and to 12 the pulse duration of the output waveform of waveform shaping circut '7 becomes smaller, with the terminal voltage of condenser 60 changing as shown at V and the output voltage of constant voltage source means 8 changing as shown at V In consequence, the output waveform of detecting device 1 changes as shown at V while the output waveform of waveform shaping circuit 7 changes as shown at V resulting in change in the interrupting point of the primary current of ignition coil 10. It is thus, possible to advance the ignition point.

As has been described above, in the system of the present invention, the output waveform of the ignition point detecting device is changed by changing the high frequency electromagnetic energy of the coupling coil of said device by means of the constant voltage source means by means of which output is changed corresponding to the rpm of engine. The pulse duration of the output wave of waveform shaping circuit is changed also in accordance with the r.p.m. of engine, and the pulse is introduced into the ignition coil through the amplifying circuit to control the primary current thereof. Since the ignition point is advanced electrically and automatically in accordance with the r.p.m. of engine, it is possible to eliminate unsatisfactory advancing of the ignition point due to friction or others as is encountered with a mechanical advancing device and also to effect automatic advancing of the ignition point simultaneously with the detection of the same.

Moreover, since the time of screening the high frequency electromagnetic energy of the first coupling coil can be changed by modifying the shape of rotary plate which crosses the interspace between the coupling coils, as shown in FIG. 9, it is possible to change the flow angle of the primary current flowing in the primary coil of ignition coil according to the shape of the rotary plate.

What is claimed is:

1. A contact-less ignition apparatus for the ignition coil of an internal combustion engine comprising:

an ignition point detecting device having a U-shaped supporting member of magnetically insulating material;

first and second coupling coils secured to the opposite inner surfaces of the supporting member and electroma-gnetically coupled to each other only through a relatively large air gap;

a high frequency generating means coupled to the first coupling coil for supplying therewith a high frequency current;

a rotatable screening means driven by the engine and disposed between the first and second coupling coils for periodically screening between the coils and substantially reducing the high frequency energy transmitted from the first coupling coil to the second coupling coil by means of absorption of the high frequency energy in the rotatable screening means; and pulse shaping circuit means coupled to the second coupling coil and the ignition coil for producing a pulse according to the output of the second coupling coil and controlling the primary current of the ignition coil in accordance with the pulse.

2. A contact-less ignition apparatus according to claim 1 further including means for supplying a constant energization voltage connected in common to said ignition point detecting device and to said pulse shaping circuit.

3. A contact-less ignition system according to claim 2 wherein means are provided for altering the output voltage of the means for supplying a constant energization voltage according to the r.p.m. of the engine so that the change in inductive voltage of said second coupling coil is controlled in accordance with the increase in r.p.m. of the engine to thereby advance the ignition point automatically.

4. A contact-less ignition system according to claim 2 wherein the pulsed output voltage generated in said second coupling coil is controlled by changing the width of said rotatable screening means whereby the current angle of the primary current flowing in the primary winding of the ignition coil is controlled.

References Cited UNITED STATES PATENTS LAURENCE M. GOODRIDGE, Primary Examiner.

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