US3650260A

US3650260A - Breakerless ignition system for an internal combustion engine

Info

Publication number: US3650260A
Application number: US879084A
Authority: US
Inventors: Raffacle Vittorio Silvera
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-11-24
Filing date: 1969-11-24
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21

Abstract

In a distributor device for an internal combustion engine having spark plug means for initiating combustion, an ignition signal generating unit for supplying the ignition pulses to the plug means comprising a first plate having at least one electrically conductive surface, a second plate rotatably supported with respect to the first plate with a predetermined gap therebetween for allowing a capacitive action to take place between the plates, the second plate having a configuration permitting variation of the capacitive effect between a maximum and a minimum value, whereby an input voltage to the unit is amplitude modulated as an output voltage.

Description

United States Patent Silvera [451 Mar. 21, 1972 [54] BREAKERLESS IGNITION SYSTEM FOR AN INTERNAL COMBUSTION Primary Examiner-Mark M. Newman Assistant Examiner-Cort Flint ENGINE Attomey-Bierman & Bierman, Harry C. Bierman and Jordan [72] Inventor: Raflaele Vittorio Silvcn, 2046 Ocean 8. Bierman Parkway, Brooklyn, N.Y. 01223 [22] Filed: Nov. 24, 1969 [57] CT In a distributor device for an internal combustion en ine hav- [211 Appl' 8794,84 ing spark plug means for initiating combustion, an ignition signal generating unit for supplying the ignition pulses to the 52 us. Cl. ..123/14s E, 315/209 T P 'l; means P 8 a fim Plate having least cleari- [51] km 9| F02 U00 cally conductive surface, a second plate rotatably supported 58 Field of Search ..l23/l48 E; 315/209 re5Pact first Pate Predetemmncd SaP therebetween for allowing a capacitive action to take place [56] References cued between the plates, the second plate having a configuration permitting variation of the capacitive effect between a max- UNITED ST PATENTS imum and a minimum value, whereby an input voltage to the unit is amplitude modulated as an output voltage. 3,217,216 11/1965 Dotto ..123/l48 E 3,473,061 10/1969 Soehner et a1 "123/148 E X 17 Claims, 5 Drawing Figures A B C D E CAPACITIVE SHAPING IGNITION 'g' i MODULATOR MODULATOR AMPLIFIER g'figfi Col w out PAIENTEDIIARZI I972 3,650,260

SHEET 2 or 2 SIGNAL AT POINT A (AMPLITUDE) TIME SIGNAL AT POINT B AMPLITUDE) DEGREES SIGNAL AT POINTC A A (AMPLITUDE) T "5"? DEGREES SIGNAL AT POINT D (AMPLITUDE) -DEGREES SIGNAL AT SCALE I INVIIIAV'UH. F/G. 4 RAFFAELE VITTORIO SILVERA BREAKERLESS IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE The present invention relates to a breakerless ignition system and, more particularly, to a breakerless distributor for use with an internal combustion engine.

In most types of internal combustion engines each cylinder is provided with a spark plug and electrical impulses must be delivered to the spark plugs of each cylinder in accurately timed relation with the movement of the pistons in the respective cylinders in order to provide for proper ignition of the fuel. The device for accomplishing this result is called a distributor. It usually comprises an arm rotatable with the crank shaft of the engine and movable into sequential electrical connection with a series of stationary terminals each of which is connected to the spark plug of a different cylinder. The rotary arm is in turn connected to a source of relatively high voltage, usually the secondary winding of an induction coil. An intermittent current is fed to the primary winding of the induction coil in synchronism with the movement of the rotor arm so that relatively high voltage surges are induced in the secondary winding in timed relation to the engagement of the rotor arm with each one of the stationary terminals. ,7

The conventional way to achieve this intermittent inducing current in the primary winding of the induction coil is by means of a switch connected between the primary winding and the battery, which switch is opened and closed intimed relation to the movement of the distributor rotor. The switch is opened and closed once for each individual cylinder firing, and the electrical circuit controlled thereby is made and broken at a precise time relative to the movement of the piston of the firing cylinder.

These distributors of the prior art have suffered from many disadvantages. The operation of the engine is directlydependent upon the gap between the switch contacts when they are fully separated. There is an unavoidable tendency for arcs to develop between the contacts as they are being separated. Even though resistors and condensers may be incorporated into the ignition circuit in an attempt to suppress this arcing, as a practical matter they succeed only in reducing the arcing but not in eliminating it entirely. The arcing causes rapid deterioration of the contact surfaces and the forming of pits in one surface and craters in the opposite surface. This greatly accelerates the wear of the contacts, causes appreciable changes in the length of the gap between the contacts, makes for point engagement between the contacts rather than engagement over an appreciable expanse of surface, and greatly increases contact resistance when the contacts are closed, thereby reducing the amount of current passing through the primary coil and thus reducing the power delivered to the spark plugs. Cleaning of the contacts, or points," as they are often called, and adjustment of the length of the gap between them, are common and frequently required maintenance operations with gasoline engines.

Attempts have been made to eliminate the above-described shortcomings by replacing the points" by a corresponding number of magnetic relays known as reed switches which are opened or closed by a permanent magnet rotated in times relation by the engine.

Another prior solution to the problems associated with conventional distributors offers to replace the points by a con ducting surface and a plurality of brushes coming into wiping relationship with the conducting surface.

A further prior solution proposes to obtain the timing pulses by interrupting a light beam hitting a photocell by a rotating mask inside the distributor. This system is susceptible to light leakage and light source burn out. In addition it requires a specially designed distributor. l

A still further prior solution proposes to produce timing pulses for the spark plugs by affecting the reluctance of a magnetic circuit by making teeth-like pole-pieces on a stator with correspondingly shaped pole-pieces on a rotor. This system requires a large magnet precisely shaped.

In addition, the above-described systems require a large number of moving elements which are expensive to make and which require the replacement of the entire distribution system by a new one; therefore, their application to existing car models becomes impossible.

It is, therefore, an object of the present invention to provide a novel breakerless ignition system and a novel breakerless distributor for use with internal combustion engines which is inexpensive and simple to manufacture.

It is a further object of the present invention to provide a novel breakerless ignition system which can be installed on existing distributors without or with only minor modifications to the distributor.

In accordance with the invention a unit called hereinafter the capacitive modulator replaces the conventional breaker point and capacitor in a distributor. This modulator comprises two or more conducting surfaces isolated from each other and having at least one surface moving with respect to another. One of the electrically conducting surfaces will rotate in synchronism with the cam of the distributor while the other surface will move in synchronism with the breaker plate of the distributor. The conducting surfaces have a geometrical shape such that when the two surfaces are rotated with respect to each other, the electrical capacitance between the two surfaces undergoes changes. This change in capacitance is converted to a corresponding change in electrical voltage and used to generate the timing pulse.

The invention further provides the use of an AC voltage which is applied to and modulated by the distributor, then demodulated, shaped and applied to the ignition coil.

The invention will become more readily apparent from the following description of preferred embodiments thereof shown, by Way of example, in the accompanying drawings, in which:

FIG. la is a top view of one of the plates of the capacitive modulator according to the invention;

FIG. lb is a top view of the other of the plates of the capacitive modulator according to the invention;

FIG. 2 is a circuit diagram representing the equivalent circuit of the capacitive modulator according to the present invention;

FIG. 3 is a block diagram of the breakerless ignition system according to the present invention; and

FIG. 4 illustrates the voltage waves at difi'erent points within the system of FIG. 3.

With reference to FIGS. la and lb it is seen that the capacitive modulator of the present invention comprises a stationary multi-surface member 10, preferably a plate having in the preferred embodiment three surfaces l1, l2 and 13. Plate 10, wh'en the capacitive modulator of the present invention is applied to an existing distributor, is mounted to the breaker plate of such distributor, preferably by means of an insulating plate. Other mounting is, however, conceivable if the breaker plate is to be eliminated or not present. Even if the breaker plate is used to mount plate 10, it can be considered as being stationary, since the breaker plate undergoes only a small movement during the vacuum process.

The capacitive modulator of the present invention further includes a member 20 having a single electrically conductive surface and mounted for rotation on the cam (not shown) of a distributor by means of an insulating sleeve at 26 and is adapted to rotate in a predetermined relationship with respect to the movements of the pistons in the engine. It is to be noted that the cam can be eliminated completely and plate 20 can be mounted directly on the shaft (not shown) driving the cam (not shown).

Plates 10 and 20'are mounted parallel with a predetermined gap between them to allow for the well known capacitive effect therebetween. It is noted that

members

10 and 20 may take the form of cylindrically or conically shaped members nestled within each other and supported for rotation as described above in connection with the preferred embodiment.

The rotating plate 20 has several lobes 21-24, one lobe for each cylinder the distributor drives, the present embodiment illustrating a plate for use with a four-cylinder engine. It is noted that there is no change in the number of areas 11 to 13 in the event that a six-lobe plate 20 is used. Areas 11-13 will be narrower to compensate for the reduced width of the lobes of a six-lobe plate as compared with those of a four-lobe plate. The areas of one lobe of rotating plate 25 and the areas of surfaces 11 and 12 are shown to be equal, while the area of surface 13 is twice the size of a lobe. This is shown for ease of illustration; however, this relationship is variable and dependent on the electrical circuit used.

The invention also provides that surfaces 11 and 12 can be placed on one member or plate, while surface 13 is placed on another member spaced therefrom with rotor 20 moving therebetween.

As a further modification, element 13 can be made in the form of a ring Within the arc of elements 11 and 12 while being beneath rotor 20.

Lobes 21-24 of plate 20 alternate with recessed portions 25 for providing the variable capacitance effect as hereinafter described.

Each of the three

surfaces

11, 12 and 13 form an electrical capacitance with respect to the surface of plate 20. The three capacitances formed by

plates

11, 12 and 13 are identified by C1, C2 and C3, respectively.

The electrical equivalent of the capacitive modulator unit shown in FIG. 2 comprises three capacitances connected in a T-circuit 30. It is noted that Cl and C2 vary while C3 is constant since during rotation plate 20 covers always equal areas of plate 13. The variation of Cl and C2 is such that the total capacitance of Cl and C2 together remains constant. How ever, Cl varies from a maximum to zero as one of the rotating lobes 21-24 is covering it or is moving away from it.

The operation of the capacitive modulator equivalent circuit is as follows:

An input voltage E which can be a DC or AC voltage, applied between Cl and C2, that is, between surfaces 11 and 12, appears across C2 attenuated (or amplitude modulated) as seen at point B of FIG. 4, the attenuation being proportional to the magnitude of C1. At this point, the modulated voltage across C2 can be picked off by a wiping contact on plate 20. C3, in the absence of a wiper, can be connected to couple the modulated voltage from C2, that is, from plate 20, thereby the necessity for a wiping contact on plate 20 is eliminated.

An AC (or pulsed) input voltage E will be amplitude modulated by the capacitive modulator and the amplitude of the pulse after modulation as E becomes a function of the position of the rotating plate 20 with respect to the stationary plate 10. This amplitude modulated output voltage E is then demodulated, sliced, and amplified by standard electronic circuits to form the high voltage timing pulse E at the secondary of the ignition coil, the steps being shown in the block diagram of FIG. 3. The wave diagrams of FIG. 4 illustrating the different waveshapes at points A-E of F l0. 3 have an initial point at at which one lobe of plate 20 is centered over surface 12. The waveshapes of FIG. 4 represent the waves generated during a 180 rotation of a four-lobe plate 20.

The novelty of using an AC input voltage modulated by the variable capacitances C1 and C2 in the distributor pennits the use of small capacitances and, therefore, small areas for surfaces 1 1-13 and 2l24.

A DC reference voltage can also be used. However, the required capacitances would be large and a multi-layer unit would be required to increase the area of the surfaces, that is, several plates and 20 mounted alternatively on a central aXlS.'

If E is a DC signal, it becomes amplitude modulated and, therefore, converted to an AC signal by the capacitive modulator of the present invention; therefore, the capacitive modulator according to the present invention is suggested for use as DC to AC electrical signal converter.

The invention provides, irrespective of whether an AC or DC reference is used, that the envelope of the modulated voltage wave E has a frequency directly related to the frequency (or speed) of the relative movement of the conducting

plates

10 and 20. Therefore, the capacitive modulator will be useful as frequency (or speed) sensor in addition to being a position sensor of two mechanical members moving with respect to each other.

It will be noted that the four surface capacitive modulator" unit can be reduced to a two-surface unit by eliminating surfaces 11 and 13. The rotating plate 20 can then be electrically grounded through the cam and a fixed capacitor added outside the capacitive modulator unit to form with C2 is capacitive attenuator.

It is noted that the use of the capacitive modulator in a new or in an existing distributor eliminates the need for points" which have been the most sensitive parts in a combustion engine directly affecting its performance.

While the invention has been explained and described with the aid of a particular embodiment thereof, it will be understood that the invention is not limited thereby and that many modifications utilizing the spirit thereof without departing essentially therefrom will occur to those skilled in the art in applying the invention to specific operating environments and conditions. It is therefore contemplated by the appended claims to cover all such modifications as fall within the scope and spirit of the invention.

What is claimed is:

1. In a distributor for an internal combustion engine having ignition means for initiating combustion, the improvement which comprises an ignition signal generating unit for supplying ignition pulses to said ignition means comprising a first member having at least two electrically conductive surfaces, an electrically conductive second member rotatable with respect to said first member with a predetermined gap therebetween for allowing a capacitive action to take place between said members, said second member having a configuration permitting variation of the capacitive effect between said second member and either of said electrically conductive surfaces, the sum of the capacitance between each of said two conductive surfaces and said second member remaining constant, whereby an input voltage to said unit is amplitude modulated as an output voltage.

2. A device according to claim 1, wherein said first and second members are plate means, said second plate means comprising a plurality of lobe means alternating with recessed portions, said ignition means comprising a plurality of ignition devices, said lobe means corresponding in number to the number of the ignition devices of said engine.

3. A device according to claim 2, wherein said first plate means comprises at least three conductive surfaces, two of such conducting surfaces having each an area substantially equal to each other, the area of the third one of said surfaces having an area substantially corresponding to the area of two lobe means.

4. A device according to claim 3, wherein each of said conductive surfaces of said first plate means substantially corresponds in area to the area of one of said lobe means.

5. A device according to claim 3, wherein said first and second surfaces of said first plate means form a first and a second capacitance with said second plate means, said third surface of said first plate means forms a third capacitance with said second plate means, said first and second capacitances being in series and said input voltage is applied between said first surface and said second surface and said second plate means.

6. A device according to claim 1, wherein said input voltage is an alternating voltage.

7. A device according to claim 2, wherein said first plate means comprises a pair of conductive surfaces having substantially equal areas, a third member having a conductive surface with an area substantially corresponding to the area of two lobe means, said second plate means being mounted for rotation between said first and third members.

8. A device according to claim 2, wherein said first plate means comprises at least three conductive surfaces, two of said conducting surfaces having substantially equal areas, the area of the third of said surfaces having an area substantially corresponding to the area of two lobe means, said first and second surfaces of said first plate means forming a first and second capacitance with said second plate means, said third surface of said first plate means forming a third capacitance with said second plate means, said first and second capacitances being in series and said input voltage being applied between said first surface and said second plate means, said third surface picking up said output voltage from said second surface.

9. In an internal combustion engine having ignition means for initiating combustion, the improvement comprising a signal generating unit, an alternating current carrier signal input to said unit, said unit having a plurality of sequentially operative capacitive means for amplitude modulating said alternating current carrier input.

10. The device according to claim 9 further comprising means for deriving a timing pulse from said unit, said means for deriving a timing pulse comprising, a demodulator for demodulating the amplitude modulated signal, shaping means for converting said demodulated signal into a square wave form, an ignition coil, and means for applying said square wave form to said ignition coil.

11. The device according to claim 10 wherein said ignition signal generating unit comprises a first member having at least one electrically conductive surface, an electrically conductive second member relatively rotatable with respect to said first member, said second member being spaced from said first member to permit a capacitive action to take place between said members, said second member having a configuration permitting variation of said capacitive action between a maximum and a minimum value whereby an input voltage to said generator is amplitude modulated as an output voltage having an amplitude, modulation and frequency directly related to the relative position and speed of the two said members.

12. The device according to claim 9 comprising a first member having a plurality of electrically conductive surfaces, an electrically conductive second member rotatably supported with respect to said first member with a predetermined gap therebetween for allowing said capacitive action to take place between said members, said second member having a configuration permitting controlled variation of the capacitive effect between a maximum and a minimum value, whereby the alternating current input carrier signal to said unit is amplitude modulated.

13. The method of conditioning an alternating input current carrier signal to an ignition coil in an internal combustion engine by use of a plurality of capacitors at least one of which is variable, comprising the steps of applying said carrier signal to said capacitors, varying the capacitance of at least one of said capacitors to attenuate and amplitude modulate said carrier signal, demodulating said amplitude modulated carrier signal, shaping said demodulated carrier signal to give it a fast rise characteristic to operate said coil.

14. The method specified in claim 13 wherein the step of modulating said input signal comprises the steps of applying said input signal to at least one plate, placing a second plate adjacent said first plate and spaced therefrom to create a capacitance between said plates, relatively moving said plates to create a varying capacitance between said plates, and then picking off the output of the said two plates.

15. The method according to claim 14 wherein the input signal is applied to two plates, one of said plates being electrically common, spacing said two plates from each other a predetermined distance whereby the sum of the capacitances of said two plates as created by relative movement of said second plate is constant.

16. The method according to claim 15 further including the step of providing a third plate adjacent said two plates, moving said second plate over said third plate to generate a capacitance therebetween, and picking off the signal from between the said third plate and the said electrically common l j In an internal combustion engine having ignition means for initiating combustion, the improvement comprising means for providing an alternating current carrier signal, a signal generating unit to which said carrier signal is applied as an input signal, said unit having a plurality of capacitors at least one of which is variable to amplitude modulate said carrier signal as an output.

Claims

16. The method according to claim 15 further including the step of providing a third plate adjacent said two plates, moving said second plate over said third plate to generate a capacitance therebetween, and picking off the signal from between the said third plate and the said electrically common plate.

17. In an internal combustion engine having ignition means for initiating combustion, the improvement comprising means for providing an alternating current carrier signal, a signal generating unit to which said carrier signal is applied as an input signal, said unit having a plurality of capacitors at least one of which is variable to amplitude modulate said carrier signal as an output.