US3683881A

US3683881A - Battery powered ignition circuit for internal combustion engines

Info

Publication number: US3683881A
Application number: US65187A
Authority: US
Inventors: Mitukuni Tutui; Hiroshi Watanabe
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1969-08-22
Filing date: 1970-08-19
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15
Also published as: GB1304083A; DE2041695A1; JPS4824564B1

Abstract

A battery powered ignition circuit for internal combustion engines comprises an additional inductance, whose induced voltage at the instant of ignition of a spark plug in each cylinder is superimposed on the induced voltage of the primary winding of the ignition circuit inductance coil to cause a restrike of the arc between the breaker points to prevent the growth of a projection on the surface of the points of the breaker and, accordingly, to increase the durability thereof.

Description

United States Patent Tutuiet al.

[54] BATTERY POWERED IGNITION CIRCUIT FOR INTERNAL COMBUSTION ENGINES [72] Inventors: Mitukuni Tutui; Hiroshi Watanabe,

both of Hitachi, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Aug. 19, 1970 [21] Appl. No.: 65,187

[30] Foreign Application Priority Data Aug. 22, 1969 Japan ..44/66023 [52] U.S. Cl... ..l23/148 DC, 123/148 D [51] Int. Cl ..F02p 3/02 [58] Field of Search...l23/l48 AC, 148 B, 148 c, 148 D, 123/148 DC, 148 P; 315/209,212

[56] References Cited UNITED STATES PATENTS 3,025,430 3/1962 Leppala ..3l5/212 X [151 3,683,881 [451 Aug. 15, 1972 1,929,651 10/1933 Ringwald ..l23/l48DC 1,440,528 l/1923 Buchenberg ..123/148D 1,693,210 11/1928 bepel ..123/14soc Primary Examiner-Laurence M Goodridge Atto'mey-Craig, Antonel1i and Hill [57 ABSTRACT A battery powered ignition circuit for internal combustion engines comprises an additional inductance,

I whose induced voltage at the instant of ignition of a spark plug in each cylinder is superimposed on the induced voltage of the primary winding of the ignition circuit inductance coil to cause a restrike of the arc between the breaker points to prevent the growth of a projection on the surface of the points of the breaker and, accordingly, to increase the durability thereof.

' s Clains, 3 Drawing Figures PATENTEDAUGIS I912 3.683.881

SECCNDARY VOLTAGE '20'00'40'00'60'00' 8000 (RPM) ROTATIONAL SPEED OF ENGINE HEIGHT OF PROJECTION O 5 lb 15 one km) RUNNING DISTANCE INVENTORS m'ruxum Tuu'm k mRosr-u wn-munse BY 01%, QM,

saw a; LU;

HTTORNEYS BATTERY POWERED IGNITION CIRCUIT FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to an improvement in battery powered ignition circuits for internal combustion engines.

In general, a battery powered ignition circuit for internal combustion engines comprises a battery as a source of electrical energy to the ignition circuit, an inductance coil for transforming the energy to a high voltage, breaker points or contacts which interrupt the primary circuit of the induction coil to permit transformation of the voltage and operate as a timer for correlating the generation of the spark with the rotation cycle of the engine, a distributor for applying the high voltage discharge in succession to the cylinders in the proper sequence and a spark plug in each cylinder to provide a fixed insulated gap across which the igniting spark is generated.

Recently, the compression ratio within the cylinder and the operating speed of the engine have been significantly increased to obtain much higher power outputs from the engine. These requirements have necessitated some changes in the ignition circuit, one being an increase in the secondary voltage which is applied to the spark plug to break down the gap between spark plug electrodes and the other being a decrease in the inductance value of the primary winding of the induction coil to increase the performance characteristics of the ignition circuit during the high speed operation of the engine.

On the other hand, maintenance-free operation of the internal combustion engine has always been a prime objective. To attain such operation in the ignition circuit, many proposals have been made to increase the durability of the contacts or points of the breaker in the ignition circuit by improving both the I materials and the design of these contacts.

Since the breaker repeats sudden interruptions of the primary current of the ignition circuit to induce a high voltage in the secondary winding of the induction coil,

become melted during the operation of the ignition cir- 0 nected in series with the primary winding of the inductance coil of the ignition circuit, with the mutual inductance between the additional inductance and the induction coil being substantially zero, i.e., the additional inductance is effectively inductively isolated from the ignition coil. The induced voltage of the additional inductance at the instant of ignition of the spark plug is superimposed on the induced primary winding voltage to increase the applied voltage between the electrodes of the breaker. Secondary arcing or restriking between the electrodes of the breaker is caused by the increased applied voltage generated by the large inductance in series with the contacts, which serves to remove the surface material on the contact surface dispersed from the opposite electrode by the first arcing during the initial separation of the contacts, to thereby prevent the growth of the projection.

The present invention will be better understood and its various objects and advantages will be more fully appreciated from the following description taken in conjunction with the accompanying drawing.

cuit. Thus, a part of the surface material of one contact tends to move towards the opposite contact by a dispensing and transferring action, and a projection is thereby formed on one surface of one contact, usually the stationary contact. The projection grows during the operation, causes variation of the ignition timing and the closing duration of the points, which has a great effect upon the performance of the engine, and reduces the durability of the points, especially for high engine speeds.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION O THE DRAWING FIG. 1 is a circuit diagram of the present invention.

FIG. 2 is a graphical'illustration showing the relafionship between the secondary voltage and the rotational speed of engine obtained by experiment.

FIG. 3 is a graphical illustration showing the relationship between the height of the projection on the contact surface, which grows during the operation of the circuit, and the running distance of the engine for comparing both the ignition circuit of the present invention and the conventional ignition circuit.

DESCRIPTION or THE PREFERRED a EMBODIMENT By detailed investigation of the growth of the projection on the surface of the points or contacts of the breaker, it has'been found that at the instant of separation of the contacts, arcing first occurs and surface material on the anode surface moves or disperses towards the cathode surface because of the superheating of the anode surface by electrons, which have an important efiect at this first arcing period, while the separation distance between the cathode electrode and anode electrode is small. After the extinguishing of the first arc, if secondary arcing or restriking at the instant of the igniting of the spark plug fails to occur, a projection on the cathode surface is: formed and grows gradually during the repetition of the interrupting operation. On the other hand, if restriking occurs at the instant of igniting of the spark plug, when a surge voltage occurs in the secondary circuit of the ignition coil and induces a very high voltage in the primary winding of the induction coil and the outer inductance in the primary circuit, the displaced material will be dissipated. During this secondary arcing period, since the separation distance of the electrodes is larger compared to the above-mentioned first arcing period and the duration of the arc is longer due to the much higher voltage available, positive ions are generated in very much larger numbers as compared to the first arcing period, which ions collide with the cathode surface to superhe'at and melt the surface, and the surface material of the cathode is removed or dispersed toward the anode surface to prevent the formation of the projection.

At first it was generally considered desirable to increase the inductance value of the primary winding of the coil to increase the voltage applied between the contacts of the breaker at the instant of ignition of the spark plug in hopes of obtaining a restriking of the arc; however, this method necessitates an increase in the turns ratio of the secondary winding to the primary winding to maintain the required high secondary voltage, and what is worse still, it decreases the secondary voltage particularly during high speed operation of the engine even with an increase in the turns ratio.

In FIG. 1, the ignition circuit is provided with a battery 10, whose output voltage in this embodiment is 12 V, in series with an ignition switch 12, which is closed during the operation of the ignition circuit. An induction coil 14 is provided which comprises primary winding 142, secondary winding 144 and laminated iron core 146, the turns ratio (a) between the primary winding and secondary winding being 100 in this embodiment and the inductance value of the primary winding (L being mH. A breaker 16 which comprises a stationary contact and a movable contact for interrupting the primary circuit current in the range from 2 to 5 A is connected between one side of battery 1 and the induction coil 14. A condenser 18 which absorbs the surge, reduces the arcing and reverses the direction of current flow in the primary circuit, thus aiding the rapidity of collapse of the magnetic field in and around the core 146, is connected across the points 16. The condenser 18 correspondingly increases the voltage induced in the secondary winding 144. A resistance unit 20 is provided in series with battery 1 to adjust the primary circuit current and a distributor 22 for connecting the high voltage discharge to the successive cylinders in the proper sequence is connected in the conventional manner between the secondary of the induction coil 14 and

spark plugs

24, 26, 28 and 30, which are positioned in respective engine cylinders. An additional inductance unit 32 is connected in series with the primary winding 142 of the coil 14 so that the mutual inductance with the induction coil 14 is substantially zero. Thus, the induced voltage at the instant of igniting of each of the

spark plugs

24, 26, 28 and 30 is applied between the electrodes of the breaker 16 on which is superimposed the induced voltage of the primary winding 142 of the induction coil 14, thereby causing a secondary arcing or restriking between the electrodes of the breaker 16 to displace the surface material on the cathode towards the anode and prevent the formation of the projection on that contact. A short-circuiting switch 34 is connected in parallel with the additional inductance unit 32 and is operated during the starting period of the engine. Since the engine is cranked by a motor driven by energy from the battery 10, it is advisable to short out the additional inductance 32 at this time to prevent the heavy drain on the battery 10 which may drop its voltage; and further,'the slow velocity of the interrupting speed of the breaker 16 may cause a failure of the interruption of the primary circuit under such conditions.

As a result of experiments on the ignition circuit explained above, it was found that the applied voltage between the electrodes of the breaker 16 at the instant of ignition of the spark plug, when operating in the range of primary circuit current from 2 to 5 A, should be determined between 190 and 250 V, particularly around 200 V, to cause a restriking having an appropriate arcing energy. lf a higher induced voltage is applied between the electrodes, too much dispersion of the surface material occurs to reduce the durability of the breaker l6.

Chart A provides experimental results showing the difference between the applied voltage at the instant of ignition of the spark plug between electrodes of the breakers of three ignition circuits having different circuit conditions, one of which is one embodiment of the present invention. In the experiment upon the three ignition circuits, both the primary circuit current which is to be interrupted by the breaker and the secondary induced voltage are set at 3.5 A and 8.0 KV, respectively.

In ignition circuit No. 1, which is one conventional ignition circuit, the inductance value of the primary winding of the induction coil (L is 5 mH and the turns ratio (a) is 100 with no external or additional inductance unit being added.

In ignition circuit No. 2, which is one embodiment of the present invention, the inductance value of the primary winding (L and the turns ratio (a) are the same as those of circuit No. 1, however, the external or additional inductance unit 32 having an inductance value of l mH is added as shown in FIG. 1.

In ignition circuit No. 3, which has been described as one original suggestion for obtaining an increased applied voltage between the electrodes of the breaker, the inductance value of the primary winding (L is 10 mH and the turns ratio (a) is 100 with no external or additional inductance being added.

It should be understood from chart A that the interrupting voltage of the primary circuit of circuit No. 2 is higher than the others and also that the method of increasing the primary inductance value itself in order to increase the interrupting voltage of the primary circuit necessitates an extreme increase in the primary inductance value before effective results are achieved.

FIG. 2 is a graph of experimental results showing the relationship between the secondary voltage and the rotational speed of engine, for the above-described experimental ignition circuits No. 1, No. 2 and No. 3, each equipped on a four cylinder internal combustion engine. The abscissa in this figure represents secondary voltage and the ordinate represents rotational engine speed. The curve 50 shows the results from the ignition circuit No. 1, curve 60 shows the results from the ignition circuit No. 2 and curve 70 shows the results from the ignition circuit No. 3. It can be seen from FIG. 2 that the secondary voltage represented by curve 60, which relates to one embodiment of the present invention is higher than that of curve 50 over the whole range of rotational speeds of the engine, and it is also seen that the secondary voltage represented by curve 70 is decreased to an extreme extent in the high rotational speed range of the engine.

FIG. 3 is a graph of the experimental results showing the relationship between the height of the projection growing on one surface of either contact of the breaker during the operation of the engine and the running distance of the automobiles equipped with the ignition circuits No. 1 and No. 2, respectively. The abscissa represents the height of the projection and the ordinate represents the running distance of the automobiles.

The curve 61 provides the minimum projection height of the breaker contact of the ignition circuit No. 2 over a corresponding running distance, and curve 62 provides the maximum projection height of circuit No.

2. The curve 51 represents the minimum projection height of circuit No. l, and curve 52 represents the maximum projection height of circuit No. 1. It would be understood that the projection height of the breaker contact of the automobile equipped with ignition circuit No. 2 is extremely reduced compared to that of circuit No. 1. Accordingly, the durability of the contacts or points of the breaker of ignition circuit No. 2 is dramatically increased.

While we have shown and described one embodiment in accordance with the present invention it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.

We claim:

1. A battery powered ignition circuit for plural cylinder internal combustion engines comprising:

a battery for supplying electrical energy to said ignition circuit;

an induction coil for transforming said electrical energy to a high voltage; said induction coil having a primary winding inductively coupled to a secondary winding, said primary winding being connected in series with said battery, said secondary winding being selectively connectable through a distributor to a spark plug in each cylinder of said internal combustion engine;

a breaker connected in series with said battery and said induction coil and having contacts for interrupting the series connection of said primary winding to said battery; a condenser connected in parallel with said breaker to absorb voltage surges generated by said breaker when interrupting the connection of said primary winding to said battery;

m ri s for effecting a secondary arcing of the breaker contacts comprising only an additional inductance connected in series with said primary winding between said battery and said primary winding, the mutual inductance between said additional inductance, saidprimary winding and said secondary winding being substantially zero.

2. A battery powered ignition circuit for internal combustion engines according to claim 1, wherein the inductance value of said additional inductance is determined so that the induced voltage of said additional inductance at the instant of ignition of each of said spark plugs is superimposed on the induced voltage of said primary winding to restrike the are between the contacts of said breaker.

3. A battery powered ignition circuit for internal combustion engines according to claim 1, wherein the inductance value of said additional inductance is such that the sum of the induced voltage of said additional inductance and said primary winding at the instant of ignition of each of said spark plugs applied between the contacts of said breaker is between 200 to 250 V, when the interrupting current of said breaker is in the range from 2 to 5 A.

4. A battery powered ignition circuit. for internal combustion engines according to claim 1, wherein short circuiting means is connected to said additional inductance for short-circuiting said additional inductance during the starting period of said internal combustion engine. V

5. In a battery powered ignition circuit for internal combustion engines including an autotransformer having a primary winding in series with a battery and a pair of. breaker contacts, means for effecting a secondary arcing of the breaker contacts including only an additional inductance connected in series with said primary winding between said battery and :said primary winding for increasing theinductance in series with said breaker contacts, said additional inductance being inductively isolated from said autotransforrner so as to preserve the turns ratio thereof.

6. A battery powered ignition circuit as defined in claim 5, wherein said autotransformer includes a secondary winding selectively connected by distributor means in sequence to a plurality of spark plugs.

7. A battery powered ignition circuit for internal combustion engines according to claim 6, wherein the inductance value of said additional inductance is such that the sum of the induced voltage of said additional inductance and said primary winding at the instant of ignition of each of said spark plugs applied between the contacts of said breaker is between 200 to 250 V, when the interrupting current of said breaker is in the range from 2 to 5 A.

8. A battery powered ignition circuit for internal combustion engines according to claim 7, wherein short circuiting means is connected to said additional inductance for short-circuiting said additional in ductance during the starting period of said internal combustion engine.

Claims

1. A battery powered ignition circuit for plural cylinder internal combustion engines comprising: a battery for supplying electrical energy to said ignition circuit; an induction coil for transforming said electrical energy to a high voltage; said induction coil having a primary winding inductively coupled to a secondary winding, said primary winding being connected in series with said battery, said secondary winding being selectively connectable through a distributor to a spark plug in each cylinder of said internal combustion engine; a breaker connected in series with said battery and said induction coil and having contacts for interrupting the series connection of said primary winding to said battery; a condenser connected in parallel with said breaker to absorb voltage surges generated by said breaker when interrupting the connection of said primary winding to said battery; and means for effecting a secondary arcing of the breaker contacts comprising only an additional inductance connected in series with said primary winding between said battery and said primary winding, the mutual inductance between said additional inductance, said primary winding and said secondary winding being substantially zero.

2. A battery powered ignition circuit for internal combustion engines according to claim 1, wherein the inductance value of said additional inductance is determined so that the induced voltage of said additional inductance at the instant of ignition of each of said spark plugs is superimposed on the induced voltage of said primary winding to restrike the arc between the contacts of said breaker.

4. A battery powered ignition circuit for internal combustion engines according to claim 1, wherein short circuiting means is connected to said additional inductance for short-circuiting said additional inductance during the starting period of said internal combustion engine.

5. In a battery powered ignition circuit for internal combustion engines including an autotransformer having a primary winding in series with a battery and a pair of breaker contacts, means for effecting a secondary arcing of the breaker contacts including only an additional inductance connected in series with said primary winding between said battery and said primary winding for increasing the inductance in series with said breaker contacts, said additional inductance being inductively isolated from said autotransformer so as to preserve the turns ratio thereof.

8. A battery powered ignition circuit for internal combustion engines according to claim 7, wherein short circuiting means is connected to said additional inductance for short-circuiting said additional inductance during the starting period of said internal combustion engine.