Patent Publication Number: US-3877453-A

Title: Ignition system for internal combustion engines

Description:
United States Patent 11 1 [111 3,877,453  
 [22] Filed: Jan. 19, 1973 Brungsberg Apr. 15, 1975 IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES [56] References Cited [75] Inventor: Heinrich-Josef Brungsberg, UNITED STATES PATENTS Ludenscheid, Germany 3,173,410 3/1965 McLaughlin 123/179 3,293,492 7/1963 Wald 315/180 [73] ASSlgl&#39;lCBZ BIOWI&#39;I, Rover! 81. C1e A.G., 3 709 20 H1973 123 14 E Mannheim, Germany 3,731,144 5/1973 McKeown 315/209 T Primary Examiner-Manuel A. Antonakas [21] App]. No.: 324,945 Assistant Examiner-James W. Cranson Attorney, Agent, or FirmErwin Saltzer [30] Foreign Application Priority Data ABSTRACT Jan. 28, 1972 Germany 2203938 The p y winding of the ignition system includes [52] U S Cl 123/148 315/209 T two serially connected sections which are energized [51] F02) 3/02 sequentially and form an effective means for storing [58] Field of Search 123/148, 179; 315/180, energy magnet: fOrm- 315/209 T 4 Claims, 2 Drawing Figures PATENTEBAPR 1 5i9?5 SHEET 1 OF 2 PATENTEDAFR I 519. 5  
 SEZEU 2 BF 2 IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION Among the various ignition systems for internal com bustion engines the conventional transformer coil system is still used most extensively. This system is predicated on the storage of energy in magnetic form but, as presently applied, has still three serious limitations:  
  1. Assuming that the life of the contact points of the interrupter is supposed to be in the order of, and not less than, about 6000 to 7000 miles, this imposes a limitation on the current of the coil to the order of about 4 Amps;  
  2. a limitation on the magnetically stored energy to the order of 30 to 50 milliwatts sec.; and  
  3. a limitation of the time constant of the primary winding to a maximum value of about 6 milliseconds.  
  The inductivity of the primary winding is determined by the stored energy and the maximum valve of the energizing current. In conventional designs the inductivity of the primary winding is in the order of4 to 10 millihenrys. The voltage of the d-c power supply or battery and the maximal admissible current determine the resistance of the primary winding. Considering a d-c power supply or battery having a voltage of 6 volts and considering the maximum permissible energizing current to be 4 Amps, then the resistance of the primary winding is 1.5 Ohms. In the case that the voltage of the do power supplies exceeds 6 volts a resistor is generally connected in series with the primary winding. The time constant of such an arrangement determined by the inductivity of the primary winding and its resistance are in the order of.2 to 6 milliseconds.  
  To fully charge an inductance requires about three times the time constant. The charging time for standard ignition coils is, therefore, 3 X 2 to 3 X 6 milliseconds, or 6 to 18 milliseconds. Considering that the charging period of the ignition coil is limited to the time during which the contact points of the interrupter are separated which time is at most 50% of the total cycle time for four cylinder engines leads to the conclusion that the full power of the ignition coil can only be obtained up to an ignition or spark frequency of 80 Hertz.  
  A four cylinder internal combustion engine requires the above spark frequency of 80 Hertz at 2500 rpm. At higher numbers of revolution the ignition energy decreases because there is not sufficient time available to fully charge the inductance ofthe ignition system. Considering a four cylinder internal combustion engine operating at full load at about 5500 rpm which is quite common, the magnetic energy which is then stored, or can be stored, in the coil system is about one-third of its possible or nominal value. The times during which the contact points of the interrupter are closed and open, respectively, are even shorter considering six cylinder engines and eight cylinder engines rather than four cylinder engines and, therefore, the energy available for ignition purposes is relatively smaller as far as the former are concerned.  
  The above figures are based on the assumption that the voltage of the d-c power supply or battery is constant. This is, however, not always the case. There are instances, particularly the starting period of an internal combustion engine, when the voltage of the d-c power supply or battery is below normal. It must be kept in mind that the energy which is available for ignition decreases when the voltage of the d-c power source decreases.  
  Other important factors to be considered are the rate of rise of the ignition voltage, and the breakdown value thereof. The rate of rise of the ignition voltage may be in the order of 350 volt/u sec. and the breakdown voltage may be in the order of 10 to 15 kV. In cases where the insulation level of the spark plugs is not sufficiently high, significant losses may occur during the entire rise time of the ignition voltage, thus decreasing the energy which is available for the purpose of ignition.  
  Transistorized coil ignition systems show a considerable improvement over the conventional, prior art or non-transistorizedignition systems which have been considered above. The former as well &#39;as the latter are predicated on magnetic energy storage. The possibility offered by transistors of switching relatively large currents without contact erosion by means of relatively small control currents resulted in an increase of the life of the contact points of the interrupter. Their life is at present in excess of 30,000 miles. The advent of the transistor made it also possible to substitute solid state circuitry for prior art mechanical switch means includ ing cam-operated contact points. Transistorized ignition systems make it possible to increase the primary energizing currents of the coil system. This, in turn, results in a decrease of the time constant and an increase of the limit frequency up to which the entire energy capable of being stored is stored in the coil system. These changes result in a decrease of sensitivity in regard to changes of the voltage of the source of d-c power. Application of transistors further results in a decrease of switching times and eliminates the problems of contact bounce, and transistorized ignition systems for internal combustion engines do not require the shunt capacitors which form an integral part of more conventional ignition systems. The former make it also possible to increase the rate of rise of the ignition voltage to about 600 volts/pt sec. and this, in turn, decreases the effect of shunt current path parallel to the spark gaps of the spark plugs. Transistorized ignition systems are, however, more expensive than more conventional coil ignition systems.  
  Another relatively novel and unconventional ignition system for internal combustion engines involves the use of electric energy stored in a capacitor rather than of magnetic energy stored in a coil system. The output of a battery is supplied to an appropriate converter whose output voltage is much higher than its input voltage, e.g. 350 Volts. A storage capacitor of about 1 ,u Farad is charged at the aforementioned elevated voltage and stores about 60 milliwatt-seconds. At the time of ignition, the aforementioned storage capacitor is discharged by the intermediary of a thyristor into the primary winding of an ignition transformer or ignition coil. The high capacitor discharge current results in a very rapid rate of rise of the ignition voltage, e.g. at 8 kV/u sec. This has the beneficial effect of producing an acceptable ignition even if the spark plugs are not clean and have a relatively low insulating level, which is particularly important in regard to starting performance at cold days. A serious drawback of the aforementioned capacitor storage ignition systems resides in the fact that the duration of the spark discharge is relatively short in comparison to the duration of the discharge in conventional ignition systems. The duration of the high-voltage discharge in conventional ignition systems is in the order of 1000 to 2000 u sec., but the duration of the high voltage discharge in the aforementioned ignition systems involving electrical storage in a storage capacitor is but 50 to 250 1.1. sec.  
  An up-dated novel ignition system for internal combustion engines would have to meet with the following requirements:  
  l. The contact points of the interrupter should have a life corresponding to a mileage of at least about 30,000 miles. showing no significant deterioration or erosion at this time. The system should be further able to allow substitution of the conventional interrupter by a solid state device, thus eliminating entirely relatively movable contacts.  
  2. Even if the voltage of the d-c power supply declines as much as 50%, the value of the ignition energy should remain substantially unaffected or unaltered.  
  3. The ignition energy should not deviate more than i from its normal value for the entire rpm range of the internal combustion engine.  
  4. The peak ignition voltage should be equal to, or larger than. 25 kV(1&#39;i 25 kV) and should have a rate of rise equal to, or in excess of, 1 kV/ p. sec.  
 I 5. The igniting sparks should have a duration equal to, or in excess of, 500 p. sec.  
 6. The cost of the system should not significantly exceed those of a conventional coil ignition system.  
  It is the object of the present invention to provide an ignition system which meets substantially with, or exceeds. the above requirements.  
 SUMMARY OF THE INVENTION tance section serially connected with said first section.  
 The system further includes means for sequentially energizing said first section and said second section of said primary winding from a d-c power source. To this end the ignition system includes switching means for initially connecting said first section and said second section serially to said d-c power source. The system further includes a shunt-circuit by-passing said second section to allow energization by said d-c power source of said first section only, which shunt-circuit includes a transistor for controlling the flow of current therein. A tertiary winding is inductively coupled with the primary winding and provides the control current for said transistor. In addition systems embodying this invention include a diode arranged to preclude current flow in said second section while said first section is being energized by a current flowing through said transistor.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a wiring diagram of a system embodying the present invention including one control transistor; and  
  FIG. 2 is a wiring diagram of a system embodying the present invention including two control transistors.  
 DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, numeral 10 has been applied to indicate a d-c power supply, or battery, to energize the ignition system. Reference numeral 7 has been applied to generally indicate an induction coil. The latter includes the secondary or high-voltage winding 5 and the primary or low-voltage winding 6. Windings 5 and 6 form an autotransformer. The low-voltage or primary winding 6 is subdivided into two serially connected sections 3 and 4. The first section 3 has a relatively small resistance and the second section 4 has a relatively high resistance. One electrode of each spark plug 9 is grounded and the other electrode of each spark plug 9 is connected by a lead to the upper end of high-voltage winding 5. The negative pole of battery 10 is grounded and connected by a lead to the upper end of winding section 3.  
  FIG. 1 shows in the right upper portion thereof four spark plugs 9 which may be periodically conductively connected to the upper end of high-voltage winding 5 by means of a rotating distributor shown at the left of the spark plugs 9. Switch 1 is operated by means of a cam mounted on the same shaft as the distributor for the four spark plugs 9. The system includes a tertiary winding 11 inductively coupled with the primary winding 6. The flow of current from the positive pole of battery 10 to the point intermediate winding sections 3,4 is controlled by switch 2 and by a solid state gate, preferably a transistor 12. Tertiary winding 11 supplies the base current for transistor 12, and thus controls the flow of current 13 from the positive pole of battery 10 to the point intermediate winding sections 3 and 4. The positive pole of battery 10 is further connected by a lead including cam-operated switch 1 and diode 8 to the bottom end of winding section 4.  
 The above circuitry or system operates as follows:  
  When interrupter contact 1 closes an initial current is allowed to flow from the positive pole of battery 10 through closed switches 2 and 1, diode 8, and winding sections 4 and 3 of primary winding 6 to the negative pole of the battery 10 which is grounded. This initial current induces a voltage in the tertiary winding 11, as a result of which a current i is caused to flow unblocking transistor 12. Hence a current path for the charging current i of winding section 3 is established. This current path extends from the positive pole of battery 10 through switch 2 and transistor 12 to the point intermediate winding sections 3 and 4 and then through winding section 3 to the negative pole of battery 10. The charging current rises linearily to a predetermined peak value which may be 12 Amps. When this value is reached, the common core of windings 5, 6 and 11 is saturated. As a result, the flow of gating current i ceases and transistor 12 returns from its conductive state to its current blocking state. During the charging period of winding section 3 a voltage was induced in winding section 4 but could not result in a current flow through winding section 4 on account of the presence of blocking or reversed biased diode 8. When the current flow through winding section 3 ceases the backvoltage in winding section decays to zero and a current flow is established from the positive pole ofbattery 10 through switch 1 and diode 8 then biased in forward direction and through the serially connected winding sections 4,3 to the negative pole of battery 10. This current which may be referred to as holding current i maintains the core of windings 5,6 and 11 in a state of saturation. Holding current i appears without time delay and the magnetic energy originally stored in the system remains unchanged.  
  Opening of switch 1 results in a conversion of the magnetic energy stored in the system into electric energy, i.e. a flow of current through the high-voltage circuit including high-voltage winding 5, the rotary distributor connecting the latter and the four spark plugs 9 and one of the four spark plugs 9. In the circuitry of FIG. 2 opening of switch 1 may result in arcing at this point. This tends to reduce the rate of rise of the highvoltage across the ends of high-voltage winding 5 as a result of the dissipation of a portion of the magnetic energy stored in the system in form of are energy. The circuitry of FIG. 2 is not subject to this limitation.  
  In FIG. 2 the same reference characters as in FIGS. 1 have been applied to indicate like parts. Hence a description of FIG. 2 can be limited to the features distinguishing the circuitry of FIG. 2 from that of FIG. 1. The former includes an additional solid state gate or transistor 13 inserted into the lead from the positive pole of battery and switch 2 to the lower end of winding section 4 including diode 8. Switch 1 controls the gate current path or base current path of transistor 13 which current path includes resistor 14 and the Zener diode 15. Thus transistor 13 is arranged to carry the holding current i, or I and switch 1 controls but the gating or base current for transistor 13. The circuitry of FIG. 2 operates as follows:  
  Closing of switch 1 supplies transistor 13 with sufficient base current to allow the flow of an initial current i,=i from the positive pole of battery 10 through winding sections 4 and 3 in series to the negative pole of battery 10. This initial current causes energization of tertiary winding 11 and the resulting current unblocks transistor 12. This establishes a path for loading current i from the positive pole of battery 10 through transistor 12 to the point of intermediate winding sections 4 and 3 and through winding section 3 to the negative pole of battery 10. The current through winding section 3 increases linearily to, say, l2 Amps. when the core of windings 5 and 6 is saturated, tertiary winding 11 de-energized and transistor 12 returned to its blocking condition.  
  The charging current i of winding section 3 induces an emf in winding section 4 not resulting in a flow of current in winding section 4 on account of the blocking action of diode 8. Upon disappearance of said emf holding current 1&#39;. immediately, i.e. without time delay, maintains the energization of auto transformer 7 which remains in a state of saturation. Upon opening of switch 1 the magnetic energy stored in the system results in the flow of current in the circuit including winding 5 and one ofthe four spark plugs 9. The presence of transistor 13 makes it possible to minimize the currents to be switched by switch 1 and to substitute, if desired. a  
 non-mechanical or solid state switch for the mechanical switch 1. The inductance of winding 5 may be kept relatively small yet resulting in a rise of voltage larger than 1 kV/usec. and in a peak voltage larger than 25 kV. Changes in the voltage of battery 10 up to 50% and in the number of revolutions of the internal combustion engine have no effect upon the energy supplied for ignition purposes. Resistor l4 and Zener diode 15 limit the holding current I I claim as my invention:  
  1. An ignition system for internal combustion engines comprising a. means forming a high-voltage circuitry including spark plug means (9) and a secondary winding (5);  
 b. means forming a low voltage circuitry including a primary winding (6) inductively coupled with said secondary winding (5), said primary winding (6) having a first small resistance section (3) allowing rapid build-up of current therein and a second high resistance section (4) serially connected with said first section (3);  
 c. switching means (1) for initially connecting said first section (3) and said second section (4) serially to said d-c power source;  
 d. a shunt-circuit by-passing said second section (4) to allow energization by said d-c power source (10) of said first section (3) only, said shunt-circuit including a transistor (12) for controlling the flow of current therein;  
 e. a tertiary winding (11) inductively coupled with said primary winding (6) and providing the control current for said transistor (12); and  
 f. a diode (8) arranged to preclude current flow in said second section (4) while said first section (3) is energized by a current flowing through said transistor(l2).  
  2. An ignition system as specified in claim 1 wherein said switching means for initially serially connecting said first section (3) and said second section (4) to said d-c power supply include a second transistor(14).  
  3. An ignition system as specified in claim 2 wherein a resistor and a Zener diode are connected in series with said second transistor, and said first section (3) and said second section,(4) of said primary Winding (6).  
  4. An ignition system as specified in claim 1 wherein said primary winding (6) has a tap arranged between said first section (3) and said second section (4) thereof, wherein the emitter of said transistor (12) and one end of said tertiary winding (11) are connected to said tap, and wherein the other end of said tertiary winding (11) is connected to the base of said transistor (12).