Booster Circuit For Ignition Systems

Abstract

A booster circuit is employed with an ignition system for an internal combustion engine to assure that sufficient energy is supplied to engine ignition means for igniting fuel in the engine at predetermined engine speeds.

Description

The present invention relates to a booster circuit for use with an ignition system employed with an internal combustion engine, and, particularly, to an improved booster circuit for an ignition system to provide suitable energy to engine ignition means for assuring the igniting of fuel in the engine at predetermined engine speeds.

In one type of conventional ignition system, combustible fuel is ignited during sequentially timed intervals synchronized with the phase of engine operation by means of breaker and associated breaker points employed with a battery, together with a mechanical rotating distributor in a well-known manner. Another type of conventional ignition system employs a magnetogenerator as a source of power which is employed with a breaker and associated breaker points, together with a mechanical rotating distributor, as is well known in the art. In recent years, ignition systems have been designed in which the breaker apparatus is replaced by electronic circuitry for performing similar functions in response to electrical timing pulses produced in synchronism with engine operation. Many of these systems have employed electronic switches and a trigger generator to actuate the switches to a conductive state for connecting voltage pulses to engine ignition means, which includes a spark plug for each cylinder of the engine.

Difficulties have been experienced with the conventional and more recent ignition systems during cranking or starting of the engine and at low engine speeds. This is due to the failure of the ignition system to provide sufficient energy to the ignition means to enable proper combustion in the engine cylinders while starting the engines and at low engine speeds. With battery-powered ignition systems, for example, in cold weather, the voltage of the battery is decreased and the parasitic load on the engine is increased caused by such factors as less efficient operation of oil and other pumps and of the starter mechanism. Furthermore, in ignition systems employing a magnetogenerator as a main source of power, at starting and low engine speeds, these generators have not provided sufficient energy for easy starting of the engine and proper performance at low engine speeds. In ignition systems employing magnetogenerators, these problems arise since the generator has its rotor geared to the engine crankshaft and the ignition system is designed to operate at optimum performance at normal engine-operating speeds. Thus, a sacrifice in performance is made at low engine speeds, such as encountered during starting of the engine.

To compensate for unsatisfactory performance of the ignition system during starting and at low engine speeds, it is desirable to provide energy booster apparatus to increase the energy delivered to the spark plugs for igniting the fuel mixture in the engine cylinders.

In the prior art, energy booster apparatus has been designed for use with ignition systems to provide increased energy delivered to the spark plugs during starting and at low engine speeds to assure appropriate firing of the fuel for easy starting and better engine performance. For the most part, these energy booster systems have employed a source of voltage and circuits with movable parts, such as a solenoid or coil operating a vibrating contact switch or breaker contacts connected in the circuit with the source of voltage, to provide increased energy in the ignition system. These energy booster systems have not been as compact and inexpensive as desirable and have not had a long operating life without malfunction. Particularly, such systems employing vibrating or breaker contacts are undesirable and cause problems since the contacts frequently burn, pit and corrode and require periodic setting. Also, since arcing occurs at the contacts during operation, the apparatus must be shielded to prevent unwanted radio frequency interference.

In accordance with the present invention, a new and improved booster circuit with novel features is provided which cooperates to provide a compact, economical and reliable arrangement for improving the firing of the engine ignition means to ignite fuel in the cylinders at predetermined engine speeds, such as when starting the engine and at low engine speeds. The present booster circuit is provided for use with an ignition system for an internal combustion engine. The ignition system may include voltage means for developing voltage pulses and for applying the pulses to ignition means in synchronism with engine operation to ignite fuel in the engine. The booster circuit preferably comprises pulse-generating means having electronic circuitry for generating pulses of energy and for applying the pulses to the ignition system for providing suitable pulses to the ignition means for igniting fuel in the engine at predetermined engine speeds.

The pulse-generating means of the booster circuit preferably includes a source of voltage, oscillator means responsive to the source of voltage for generating a series of pulses and coupling means responsive to the series of pulses for applying the pulses of energy to the ignition system. The source of voltage in the booster circuit may be provided by a battery and means may be provided for alternatively connecting the battery to the oscillator means or to the output of the voltage means of the ignition system for applying voltage of one polarity to the battery for charging the battery after the engine is operating at normal engine-operating speeds.

The booster circuit of the present invention is particularly suited for use with capacity-discharge ignition systems, which usually comprise a voltage source provided by a magnetogenerator charging a capacitor, controllable switch means for selectively completing a circuit with the capacitor and the engine fuel ignition means. The controllable switch means usually has a control terminal responsive to a suitable control signal to actuate the switch means to complete the circuit and trigger means is provided for producing the control signal applied to the control terminal for actuating the controllable switch means. One such capacity-discharge ignition system is shown and described in U.S. Pat. No. 3,311,783, of Gibbs et al. and of common assignee herewith. In such capacity-discharge ignition systems, the booster circuit is preferably connected to the capacitor to increase the energy stored by the capacitor for providing sufficient energy when the capacitor is discharged to properly ignite the fuel in the engine for easy starting and good performance of the engine.

Furthermore, the booster circuit of the present invention may be coupled to the trigger means of ignition systems that employ trigger means to generate a control signal to actuate electronic switches which complete circuits from a voltage source to the engine fuel ignition means, as described above. The trigger means in such ignition systems are usually provided by magnetogenerators which have their rotors geared to the engine crankshaft. In this arrangement, the booster circuit aids in providing a suitable signal from the trigger pulse-generating means for assuring proper actuation of the electronic switches upon starting of the engine and at low engine speeds. Preferably, the booster circuit with this type of ignition system provides pulses of energy in the magnetic circuit of the trigger-generating means to assure that a suitable control signal is generated by the trigger-generating means to actuate the electronic switch.

For a better understanding of these and other features and advantages of the present invention, reference is made to the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating an overall ignition system and booster circuit in accordance with one form of the present invention;

FIG. 2 is a block diagram illustrating another overall ignition system and booster circuit in accordance with another form of the invention;

FIG. 3 is an electrical schematic diagram illustrating an ignition system employed with one embodiment of the booster circuit in accordance with the form of the present invention shown in FIG. 1;

FIG. 3a is an electrical schematic diagram illustrating an alternative form for a portion of the circuit of FIG. 3;

FIG. 4 is a schematic diagram illustrating another overall ignition system employed with the booster circuit in accordance with the form of the present invention shown in FIG. 10;

FIG. 5 is an electrical schematic diagram illustrating another overall ignition system and booster circuit in accordance with the form of the invention shown in FIG. 2;

FIG. 6 is a planned view of an apertured plate trigger pulse-generating apparatus preferably employed with the ignition system of FIG. 5;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 6; and

FIG. 8 is a schematic diagram illustrating still another overall ignition system employed with the booster circuit in accordance with the form of the present invention shown in FIG. 2.

Referring now to the embodiment of the invention illustrated by way of example in FIG. 1, there is represented therein an ignition system and booster circuit in use in conjunction with an engine 10 which may be a conventional gasoline engine. For purposes of illustration, it will be assumed that the engine 10 has four cylinders, each with an associated spark plug for igniting combustible fuel in the corresponding cylinder, and that the engine is of the usual four cylinder type. The proper timing relation for firing fuel in the engine cylinders is provided by engine ignition means 12, which will ordinarily comprise circuitry including four spark plugs, one for each cylinder of engine 10. The ignition system is provided with voltage means 14 which is connected to engine ignition means 12. The function of the voltage means is to provide voltage pulses to the engine ignition means in sequence with engine operation so that each voltage pulse fires an appropriate spark plug at the proper time.

There is shown employed with the ignition system of FIG. 1 a booster circuit 16 which is connected to voltage means 14. Preferably, when the engine 10 is being started and until it reaches a predetermined speed, the booster circuit generates pulses of energy, which may be pulses of voltage or current, and applies them to the voltage means for providing suitable pulses to the ignition means for assuring the proper ignition of the fuel in the engine. Depending on the particular type of the voltage means employed, the booster circuit 16 may be connected directly to the line between voltage means 14 and engine ignition means 12 to apply pulses directly to the engine ignition means for assuring ignition of the fuel in the engine cylinders. In this manner, the booster circuit assures easy starting of the engine and proper operation of the engine at predetermined engine speeds. Since most ignition systems are developed to operate for optimum performance of the engine at normal engine-operating speeds, the predetermined engine speeds at which it is desirable to employ the booster circuit are governed by the particular operation of the engine and the normal range of engine-operating speeds, the booster circuit being particularly useful at speeds below the range of normal engine-operating speeds, as when starting the engine and at low engine speeds.

FIG. 2 illustrates another form of an overall ignition system which may be employed with the booster circuit of the present invention. The ignition system is shown in use with an engine 20, which may be a conventional gasoline engine having six cylinders, for example. The proper timing relation for firing the fuel in the engine cylinders is provided by ignition means 22 which includes circuitry having a spark plug for each cylinder of engine 20. The function of the remainder of the ignition system of FIG. 2 is to provide the appropriate voltage pulses to engine ignition means 22 in sequence so that each voltage pulse fires the proper spark plug at the proper time. To provide the proper voltage pulses, a voltage source 24 is employed which may be a conventional DC battery or a voltage generator which is driven from engine crankshaft 26 by way of appropriate gearing 28, as shown in FIG. 2, so as to produce at output terminal 30 of the voltage source a train of pulses in synchronism with rotation of the crankshaft 26. The gearing 28 is such as to provide the desired integral multiple relationship between the frequency of rotation of crankshaft 26 and the frequency of recurrence of pulses at output 30 of voltage source 24.

The voltage output from voltage source 24 is supplied to controllable switch means 32. The switch means 32 has, in this example, six output connections 34, 36, 38, 40, 42 and 44, each of which is effective to connect the output voltage from voltage source 24 to a different particular one of the spark plugs in the engine ignition means 12, depending upon which of input lines 46, 48, 50, 52, 54 and 56 is supplied with a trigger control signal for triggering a particular switch means connection. More specifically, input lines 46, 48, 50, 52, 54 and 56 conduct trigger control signals from trigger means 58 to different ones of six solid-state-switching circuits in the switch means, for example, to actuate a particular one of the solid-state-switching circuits to connect the output voltage of voltage source 24 to fire one of the six spark plugs connected to one of the output lines 34, 36, 38, 40, 42 and 44. The six solid-state-switching circuits are preferably provided by six silicon-controlled rectifiers. Therefore, to produce firing in any one of the six cylinders associated with engine ignition means 22, it is only necessary to apply a trigger control signal to the appropriate one of the trigger input lines 46-56 to render conductive the appropriate one of the solid-state-switching circuits in switch means 32, thereby permitting current to flow from the voltage source to the appropriate one of the spark plugs in the engine ignition means.

To generate the necessary trigger control signals at the desired times in relation to the phase of engine operation for which fuel combustion is desired, trigger means 58 having output leads 46-56 is provided, as previously stated. The trigger means preferably comprises a magnetogenerator having a number of conductors equal to the number of cylinders of the engine, spaced from each other circumferentially around the center, and a rotor having flux-generating means, which is rotatable about its center so as to induce pulses sequentially in the several conductors, as will be explained more fully hereinafter in connection with detail schematic circuit diagrams. The rotor of the trigger generator may be geared to crankshaft 26 of engine 20 by way of gearing 28 so that trigger control signals are produced by the generator at a rate in sequence with engine operation to actuate the switch means to connect the voltage source to fire the appropriate spark plug. The trigger means is arranged so that trigger control signals are produced at its output lines on the proper lines for effecting the desired sequence of the spark plug firing, this sequence being selected in appropriate fashion for the particular engine application according to principles well known in the art.

In other embodiments of the invention, as will be explained in regard to the detailed schematic diagrams, a distributor may be provided in the engine ignition means. In this instance, the ignition means will have the output terminals of the distributor connected to different ones of the spark plugs. Also, in a system employing a distributor, the switch means need include only one switching device connected to the voltage source and adapted to connect the voltage source to the single input terminal of the distributor. More specifically, the switching device, which preferably is provided by silicon-controlled rectifier, would be effective to connect the output voltage of voltage source 24 to the input terminal of distributor in engine ignition means 22. In this system, only one input line would be employed to conduct control signals from trigger means 58 to the switching device in switch means 32. The trigger means 58 in this arrangement would preferably comprise circuit means including a coil supported by a stator and a rotor having magnetic flux-generating means, which is rotated about its center so as to have its magnetic field generate control signals in the coil for triggering the switch means 32. The rotor of the trigger means would be geared to the crankshaft of the engine by way of gearing so that the trigger control signals are produced by the trigger means at a rate in sequence with engine operation to actuate the switch means to connect the voltage source to the distributor, which has its rotor geared to the engine crankshaft.

Ignition systems of the types schematically represented in FIG. 2 are preferably employed with a booster circuit generally designated 60, which preferably comprises pulse-generating means having electronic circuitry for generating pulses of energy and for applying the pulses to the voltage source or the trigger means or both, as indicated in FIG. 2. The ignition booster circuit is provided to apply pulses of energy, which may be current or voltage pulses or pulses of magnetic energy, to the ignition system for assuring igniting of fuel in the engine for optimum performance of the engine. Preferably, the booster circuit provides voltage pulses to the voltage source to assure that the output pulses on line 30 are of sufficient magnitude to fire the spark plugs of the engine at low engine speeds. As shown in FIG. 2, the booster circuit is coupled to the trigger means, which, as previously described, preferably includes a magnetogenerator having a magnetic circuit. In this arrangement, the booster circuit preferably includes a coil to which pulses are applied to generate magnetic energy for increasing the magnetic energy in the magnetic circuit of the trigger generator, thereby assuring the production of suitable signals by the trigger means applied to the control switch means to properly actuate the switch means to permit the voltage source to be connected to the ignition means.

Referring to FIG. 3, a detailed schematic diagram of a conventional battery-type ignition system is shown employed with one form of a booster circuit, generally designated 70, in accordance with the present invention. The ignition system of FIG. 3 is of the general type represented in FIG. 1. In FIG. 3 the ignition system includes a storage battery 72 having its negative terminal connected to electrical ground and its positive terminal connected to an ignition switch 74. The ignition switch 74 connects one side of the battery to one side of a timer circuit 76, which includes the usual cam 78 and breaker points 80. A condenser 84 is normally connected across the breaker points 80 to absorb reflected primary energy and to suppress breaker contact arcing. The other side of breaker points 80 is connected to primary winding 88 of an ignition transformer 90. Secondary winding 92 of ignition transformer 90 is magnetically coupled to the primary winding 88 and is connected with the primary winding at terminal 94. The other side of the secondary winding is connected in a conventional fashion through a distributor, generally designated 96. Distributor contact arm 98 is geared to rotate in synchronism with engine operation to sequentially connect the voltage pulses from the secondary winding to the output terminals 100, 102, 104 and 106 of the distributor to fire each spark plug, generally designated 108, four spark plugs being shown by way of example, one spark plug being connected to each of the output terminals of the distributor in a conventional manner.

The ignition system thus far described conforms to a conventional battery-type ignition system employed in automobiles. In operation, when the ignition switch 74 and breaker points 80 are closed, current flows through the primary winding 88 of ignition transformer 90. This current developes a magnetic field about both induction transformer windings. When the breaker points 80 are opened by cam 78, current flow is interrupted in primary winding 88 and the established magnetic field suddenly collapses. The collapsing magnetic field induces a high-voltage pulse in secondary winding 92 which is conducted through distributor 96 to fire the appropriate one of the spark plugs 108.

In battery ignition systems of the type described above, these systems function satisfactorily over normal working speeds of the engine. However, difficulties have been experienced with these systems in producing adequate ignition at relatively slow starting speeds of the engine and, particularly, under unfavorable conditions, such as cold weather which may cause partial deplete of the battery charge and increased parasitic loads on the engine. In order to provide increased energy for adequate ignition to start the engine and to insure dependable operation of the engine at low speeds, the booster circuit 70 is provided.

The booster circuit 70 in FIG. 3 comprises a battery 120, which has its positive terminal connected to electrical ground and its negative terminal connected to one terminal 122a of switch 122. The other terminal 122b of switch 122 is electrically connected to a transformer oscillator circuit, generally designated 124, which is adapted to provide high-voltage output pulses to coupling circuit 126. The coupling circuit 126 in response to the pulses from the oscillator circuit applies pulses of energy to the ignition system to increase the energy delivered to the distributor 96 by the voltage means of the ignition system. The coupling circuit 126 includes a rectifier circuit means, as will be explained more fully hereinafter. The output of the coupling circuit is connected by electrical line 128 to the ignition system between breaker points 80 and ignition transformer 90, as shown in FIG. 3.

The transformer oscillator circuit 124 comprises a transformer, generally designated 134, having a primary winding 136 and two secondary windings 138 and 140. Primary winding 136 has one end connected to terminal 122b of switch 122 and its other end connected to the collector of transistor 142, which has its emitter connected to electrical ground. Also, there is connected between terminal 122b of switch 122 and electrical ground a voltage divider circuit comprising resistors 144 and 146. One end of secondary winding 138 is connected between resistors 144 and 146, and the other end of secondary winding 138 is connected to the base of transistor 142. Secondary winding 140 of the transformer has one end connected to electrical ground and its other end connected to the coupling circuit 126. A zener diode 148 is connected between the collector and emitter of transistor 142 to protect the transistor from high transient voltages.

The coupling circuit comprises a diode 127 having its anode connected to the output of secondary winding 140 of transformer 134 and having its cathode connected to the anode of silicon-controlled rectifier 129, which has its cathode connected to output line 128. The coupling circuit also includes a capacitor 130 which has one plate connected to the cathode of diode 127 and its other plate connected to electrical ground. Control terminal 129a of silicon-controlled rectifier 129, which is responsive to a control signal for actuating the rectifier to its conductive state, is connected through biasing resistor 131 and zener diode 132 to the cathode of diode 127 and capacitor 130, as shown in FIG. 3. The zener diode 132 is so poled that it is normally nonconductive until capacitor 130 is charged to a predetermined potential by the output of transformer oscillator 124. Preferably, a resistor 133 is connected between the control terminal and cathode of silicon-controlled rectifier 129. Resistor 133 provides a desensitizing resistance to make the rectifier less susceptible to transient voltages which might turn on the silicon-controlled rectifier at undesired times. The desensitizing of the silicon-controlled rectifier may be provided internally so that resistor 133 may be unnecessary.

In operation of booster circuit 70 of FIG. 3, when switch 122 is closed, energizing the booster circuit to produce pulses for the ignition system, transistor 142 is initially biased to its conductive state by the potential applied to its base through resistor 144 and secondary winding 138. With the transistor in its conductive state, current flows through primary winding 136 and the transistor and this results in a voltage pulse being induced in secondary windings 138 and 140. The voltage pulse induced in secondary winding 138 causes the transistor 142 to become nonconductive. The transformer 134 steps up the voltage of battery 120 and the voltage is applied to the coupling circuit, which applies pulses to the ignition system for assuring an ignition pulse of adequate energy applied to the ignition transformer for causing firing of the spark plugs. When the voltage induced in secondary winding 138 by primary winding 136 drops below the potential required to bias the transistor to its nonconductive state, then the transistor returns to its conductive state to permit current to flow through primary winding 136 and the transistor, repeating the cycle to produce another high-voltage pulse in secondary winding 140.

The high-voltage positive pulses induced in secondary winding 140 are conducted through diode 127 to charge capacitor 130. When the voltage stored in capacitor 130 has reached a predetermined value sufficient to cause breakdown of zener diode 132 rendering it conductive, the control terminal 129a of silicon-controlled rectifier 129 will have a positive potential applied thereto from capacitor 130 so that rectifier 129 is actuated to its conductive state to pass current. When silicon-controlled rectifier 129 is actuated to its conductive state, capacitor 130 is suddenly discharged through rectifier 129 and line 128 producing a pulse applied to primary winding 88 of ignition transformer 90. The high-voltage pulses thereby induced in secondary winding 92 are applied to the appropriate one of the spark plugs through the distributor to assure adequate firing of the spark plugs.

The arrangement of the booster circuit and ignition system of FIG. 3 comes within the overall block diagram arrangement shown in FIG. 1. Although the booster circuit is not connected to the voltage means for the ignition system directly, it is connected between the voltage means, which is provided by battery 72 and timer 76, and the ignition transformer 90 so that the pulses from the booster circuit are applied directly to the ignition transformer for firing the appropriate spark plug through the distributor. The frequency at which the oscillator in the booster circuit operates is preferably sufficient to permit the occurrence of several oscillations or pulses across each spark plug during the appropriate firing interval for each particular spark plug. Thus, the booster circuit with the ignition system of FIG. 3 provides multiple sparks to the spark plug to assure easy starting of the engine and optimum performance of the engine at low speeds. If a good air-fuel mixture is not available at the time of the first firing of the spark plug, there is now an opportunity for a second or third spark to ignite a fresh portion of the charge in the engine cylinder, thereby assuring complete combustion and easy starting of the engine. The transformer oscillator 124 of the booster circuit oscillates at a frequency, which preferably is on the order of 3,000 cycles per second, to provide the multiple pulses to each spark plug during each combustion stroke in the engine cylinders. Of course, the pulse produced by the battery 72 and timer circuit 76 of the ignition system is still supplied to the spark plug. After the pulse created by the ignition system occurs, when breaker points 80 are opened, pulses are still conducted to the ignition transformer from the booster circuit.

The switch 122 in booster circuit 70 may be provided by a switch which is adapted to be operated manually so that upon starting the engine and up to a desired engine speed, the operator can close switch 122 to have the booster circuit provide multiple sparks to the spark plugs. After the engine reaches a desired or predetermined speed, or after the engine has had an opportunity to warm up, the booster circuit can be deenergized by opening switch 122. Of course, switch 122 could be adapted to be opened and closed automatically by a speed-sensitive coupling arrangement, for example, so that switch 122 would be closed wherever the engine is operating at a speed below a predetermined engine speed.

FIG. 3a illustrates an alternative form for a portion of the booster circuit of FIG. 3. In the modified arrangement of FIG. 3a, parts similar to those in the structure of FIG. 3 are identified by the same number designator with the addition of primes thereto. The primary difference between the circuits of FIGS. 3 and 3a lies in the use of the battery of the ignition system to provide the power for the booster circuit, rather than employing a separate battery in the booster circuit. As shown in FIG. 3a, a separate battery for the booster circuit has been eliminated and the battery 72' of the ignition system is connected across the voltage divider circuit, which comprises resistors 144' and 146'. Battery 72' has its negative terminal connected by lead 160 to the grounded terminal of resistor 146' in the booster circuit and has its positive terminal connected by lead 162 to terminal 122a' of switch 122'. In this arrangement, transistor 142' must be of the NPN type as shown in FIG. 3a, rather than the PNP type as shown in FIG. 3, but the oscillator circuit of FIG. 3a operates in the same manner as described in regard to the oscillator circuit of FIG. 3. This arrangement saves the use of a separate battery in the booster circuit, and, otherwise, the booster circuit and ignition system operate in the same manner as described in regard to the booster circuit and ignition system of FIG. 3.

Referring to FIG. 4, there is shown a conventional magneto-type ignition system with which a booster circuit, generally designated 200, is employed. The ignition system of FIG. 4 is of the general type represented in FIG. 1 and includes a magnetoinduction generator generally designated 202 for providing the pulses of voltage to fire the spark plugs of the engine. The magnetoinduction generator is of the conventional type having a rotor 204 with a permanent magnet having north and south poles, the rotor being driven through appropriate gearing by the engine crankshaft. The magnetogenerator also includes two coils forming a transformer having a primary winding 206 and a secondary winding 208. The primary winding at one end is connected to electrical ground and at its other end is connected to electrical ground through breaker points 210, which are actuated open at appropriate times by cam 212, which is geared to the engine crankshaft, in a conventional manner. A condenser 214 is connected across the breaker points to absorb reflected primary energy and to suppress contact arcing at the breaker points. Secondary winding 208 has one end connected to electrical ground and its other end connected to a distributor, generally designated 216. The distributor 216 is of the usual type having a rotatable contact arm 220 geared to rotate in synchronism with engine operation and adapted to sequentially contact its four output terminals 222, 224, 226 and 228. A spark plug is connected to each of the output terminals of the distributor, each spark plug being designated 230.

In operation of the ignition system of FIG. 4, as the permanent magnet rotor 204 rotates, an alternating magnetic flux is created causing a buildup and collapse of flux lines within primary winding 206, resulting in an induced voltage within the primary winding. At the point where flux reversal occurs in primary winding 206, the maximum voltage is induced in the primary winding of the magneto. At that instant, the breaker contacts 210 are actuated open by cam 212 and current flow is interrupted in primary winding 206. When this occurs, the fast collapse of the magnetic field in the primary winding 206 will induce a high voltage in secondary winding 208. The voltage induced in secondary winding produces current which is conducted through distributor contact arm 220 to fire the appropriate one of the spark plugs in a conventional manner.

Usually, with a magneto-type ignition system as shown in FIG. 4, the starter motor or cranking means is adapted under optimum conditions to turn the engine, and hence the rotor 204 of the magneto, at a speed sufficient to produce voltage pulses to fire the spark plugs. However, under unfavorable conditions, such as during cold weather when the parasitic load on the engine being increased, the rate of turning the engine crankshaft may be greatly reduced. Thus, it may be difficult to provide adequate ignition at the relatively low starting speeds and until the engine reaches normal operating speeds. Thus, it is desirable to employ the booster circuit of the present invention with magnetoignition system to provide additional energy to the spark plugs when starting the engine.

The booster circuit 200 of FIG. 4 is schematically shown in a block form and is preferably identical to the booster circuit 70 shown in FIG. 3. Since the booster circuit 200 is preferably the same as booster circuit 70 of FIG. 3, its operation will not be described again in detail. As shown in FIG. 4 the booster circuit is electrically connected to the ignition system between the breaker points 210 and the primary winding 206 of the magnetogenerator. The booster circuit 200 operates independent of the engine to provide pulses of energy, voltage pulses, to the engine spark plugs. When the breaker points 210 of the ignition system of FIG. 4 are closed, the pulses generated by the booster circuit are connected directly to ground. When the breaker points are opened by cam 212 and one of the spark plugs is ready to be fired, the series of pulses from the booster circuit is applied to primary winding 206, and, as a result, a series of pulses is induced in the secondary winding and conducted to the appropriate spark plug to be fired through the distributor. When the breaker points are closed, the booster circuit is again connected to electrical ground through the breaker points 210. After the engine has started and reached a desired speed or operating condition, the booster circuit can be deenergized by opening the switch in the booster circuit, as explained in regard to the booster circuit 70 in FIG. 3.

The ignition system shown in FIG. 4 is known in the art as a high-tension ignition system. In high-tension ignition systems, the high voltage sufficient to fire the spark plug is generated in a secondary winding of the magneto and is conducted directly to the spark plug. It should be appreciated that the booster circuit of the present invention will work equally well with a low-tension type of magnetoignition system, which has a voltage step-up transformer located near the spark plug. In the low-tension type of the magnetoignition system, the booster circuit would preferably be connected to the winding of the magnetogenerator.

FIG. 5 is a schematic circuit diagram illustrating a capacity-discharge ignition system with which a preferred embodiment of a booster circuit 300 is employed in accordance with the present invention. The capacity-discharge ignition system shown in FIG. 5 is of the type shown in block diagram form in FIG. 2. The ignition system portion of the circuit of FIG. 5 is of the type shown and described in detail in U.S. Pat. No. 3,311,783, entitled "Ignition System With Electronic Distribution and Control," of Gibbs et al. and of common assignee herewith. To provide an understanding of the ignition system with which the booster circuit may be employed, the following brief description of the ignition system is set forth. In the capacity-discharge ignition system of FIG. 5, the engine spark plugs are divided into two sets, a first set 302, 304, 306, 308, 310 and 312 and a second set 314, 316, 318, 320, 322 and 324, each set being fired from two capacitor pulsing circuits. Of course, the number of spark plugs may vary and a capacity-discharge ignition system with only one capacitor can be employed, as described in U.S. Pat. No. 3,311,783, with the booster circuit. It should be appreciated that each of the 12 spark plugs shown in FIG. 5 is associated with a different cylinder of the engine, and each responds to a voltage pulse applied across it during the combustion stroke in the cylinder to ignite the fuel therein. In FIG. 5, the pulses to fire the spark plugs are generated in output winding, generally designated 325. The pulses from output winding 325 are stored in capacitive means 328 and capacitive means 330, the polarities of the voltages developed across the respective capacitive means preferably being the same polarity with respect to a reference potential, as will be explained more fully hereinafter. The capacitive means 328 and 330 are discharged through individual spark plugs of the associated first and second sets in synchronism with engine operation.

More specifically, spark plug 302, for example, has one of its terminals grounded and its other terminal connected to one terminal of secondary winding 332 of a voltage step-up transformer 334, the other terminal of the secondary winding being connected to electrical ground. Primary winding 336 of transformer 334 is connected between electrical ground and the cathode of silicon-controlled rectifier 338. A trigger coil 340a of a trigger pulse generator (which will be described hereinafter) is connected in series with diode 342 between the control terminal and the cathode of silicon-controlled rectifier 338. The polarity of diode 342 is such that only the positive-going portion of a trigger control signal generated in trigger coil 340a is applied to the control terminal and this positive pulse serves to actuate the silicon-controlled rectifier to its conductive state. A resistor 344 is connected between the cathode and control terminals of the silicon-controlled rectifier and serves to maintain a relatively low impedance between these terminals to stabilize the silicon-controlled rectifier.

Capacitive means 330 is connected to the anode of silicon-controlled rectifier 338 in ignition circuit 346 and each of the anodes of the silicon-controlled rectifiers associated with spark plugs 304, 306, 308, 310 and 312, as shown in FIG. 5. The corresponding anode of each of the silicon-controlled rectifiers associated with spark plugs 314, 316, 318, 320, 322 and 324 are similarly directly connected to capacitive means 328. Each of the 11 other ignition circuits has the same construction and operation as ignition circuit 346, and therefore only ignition circuit 346 is described in detail.

The charging of capacitive means 328 and 330, which may be provided by ordinary capacitors, is provided by output winding 325, which is part of a conventional magnetoinduction generator (not shown). The generator may have a rotating magnet armature which is driven in rotation through appropriate gearing by the crankshaft of the engine in the usual manner. In this arrangement, there is produced across output winding 325 a voltage wave form of alternatingly opposite polarity. Opposite ends of output winding 325 are connected in a split-bridge rectifier circuit, generally designated 348. The split-bridge rectifier circuit comprises a first diode 350 having its anode grounded and its cathode connected to one end 325a of winding 325, a second diode 354 having its anode connected to end 325a of winding 325 and its cathode connected to capacitor 328, a third diode 356 having its anode grounded and its cathode connected to the other end 325b of winding 325 and a fourth diode 360 having its anode connected to end 325b of winding 325 and its cathode connected to capacitor 330. The function of the split-bridge rectifier circuit is to apply pulses to capacitors 328 and 330 to charge them alternatively to a positive voltage. Means is provided for limiting the maximum amplitude of pulses stored by each of the capacitors, comprising resistor 362 and zener diode 364 connected in parallel with capacitor 328, and resistor 366 and zener diode 368 connected in parallel with capacitor 330.

The trigger control pulses for actuating each of the silicon-controlled rectifiers to their conductive state for permitting discharge of the associated capacitor for firing the spark plugs in sequence are generated in the trigger coils 340a-340l, shown in FIG. 5. The twelve coils, one for each spark plug of the engine, are provided in a trigger pulse generator which has the twelve coils spaced circumferentially from one another about a center. FIGS. 6 and 7 show a suitable preferred physical form for a trigger pulse generator. In FIGS. 6 and 7 trigger pulse generator, generally designated 400, has a magnetic rotor assembly, generally designated 402, arranged to rotate about the axis of shaft 404 in response to engine operation, that is, shaft 404 of the rotor is geared to the crankshaft of the engine through appropriate gearing (not shown).

Each of the 12 trigger coils 340a-340l is wound on a bobbin which surrounds a core of magnetic material, such as coil 340a wound on bobbin 406 which surrounds a core 408, shown in FIG. 7. Each of the coil assemblies is supported by a U-shaped member of magnetic material, such as U-shaped members 410 and 412 around coils 340a and 340d, one U-shaped member being provided for each coil assembly, each of which members extends from an apertured plate 414 around the remote end of the coil assembly and back to the plate 414. Each such U-shaped member provides an individual, separate, short, low-reluctance path for magnetic flux from the core assembly back to the apertured plate 414, by way of the two opposite sides of the U-shaped member. Each of the coil and U-shaped member assemblies is supported by the circular apertured plate 414 of magnetic material. A circular aperture, such as aperture 416 for coil 340a and its assembly, is provided in plate 414 in alignment with each of the coil assemblies, each aperture preferably having a diameter somewhat greater than that of the corresponding core for each coil assembly.

As shown in FIGS. 6 and 7, the trigger coil assemblies, such as associated with coil 340a, are mounted in line with the apertures in the apertured plate 414 and electrical connection is provided by way of leads, such as leads 418 and 420 for coil 340a, which are connected in the ignition system circuit as shown in FIG. 5. The 12 apertures in apertured plate 414, one for each coil assembly, are divided into two sets of six each, each set being disposed along a circle of different radius. The shaft 404 provides an input drive shaft which is mechanically coupled to the crankshaft to provide rotating input for the rotor assembly 402. The rotor arm 422 is double-ended in that the rotor arm extends in opposite directions from the axis of rotation thereof, so as to provide two poles 424 and 426, pole 424 being positioned so as to pass closely over the outer circle of apertures and pole 426 being arranged to pass closely over the inner circle of apertures. The rotor assembly includes a disc-shaped magnet 428 surrounding the rotor shaft 404 and supported for rotation about the axis of the shaft and is located between the rotor arm 422 and aperture plate 414, as shown in FIG. 7. The disc-shaped permanent magnet is faced polarized as indicated thereon in FIG. 7. The two poles 424 and 426 of rotor arm 422 and the apertures in plate 414 are arranged so that they induce pulses alternatively in the coils placed behind the two sets of apertures, that is, first in a coil in the outer circle and then a coil in the inner circle. A more detailed description of the circuitry and construction of a trigger pulse generator as shown in FIGS. 6 and 7 is disclosed in detail in the above-mentioned patent of Gibbs et al.

In operation of the trigger pulse generator in FIGS. 6 and 7, when the rotor arm 422 is rotated so as to move the poles 424 and 426 over the region of the apertured plate 414 between successive apertures, the low magnetic reluctance of the plate 414 causes the magnetic flux generated by magnet 428 to pass substantially entirely from one pole, through plate 414 and back to a magnet 428 without substantial fringing of the magnetic flux through the coil assemblies aligned with the apertures. However, when the pole 424 reaches the edge of one of the apertures, magnetic flux formerly passing through the aperture plate begins to be transferred to a path extending through the core, such as core 408 and thence through the U-shaped member 410 back to the apertured plate and magnet 428. As the pole 424 rotates further toward exact alignment with the aperture, this flux through the core of the coil assembly increases rapidly and thereafter decreases rapidly as the pole passes from the center of the aperture to the trailing edge of the aperture. The result is the generation of a positive pulse and a negative pulse of voltage in sequence across the trigger coil.

When the positive and negative voltage waveform is produced across each trigger coil, such as trigger coil 340a, the positive pulse is applied to the control terminal of silicon-controlled rectifier 338, in this example, to render it conductive, thereby permitting the associated capacitor 330 to discharge through rectifier 338 and primary winding 336 of the ignition transformer to fire spark plug 302. The same action occurs in sequence in the 11 other ignition circuits to fire each of the other 11 spark plugs in synchronism with engine operation. Thus, the normal and desired order of events with respect to any spark plug and its associated ignition circuit is that first the associated capacitor should be charged to the full value of the charging pulse applied thereto, then a trigger pulse will render one of the silicon-controlled rectifiers connected to that capacitor conductive to permit the capacitor to discharge and fire the associated spark plug, and then the silicon-controlled rectifier will become nonconductive so that the next capacitor-charging pulse can be effective to charge the capacitor again.

This type of high-frequency ignition system, that is, the capacity-discharge ignition system, has proved to be very advantageous and it is desirable to use such ignition systems for replacement of conventional magnetoignition systems employing breaker point apparatus and distributors. Under optimum conditions the starting motor used to start the engine, with which the capacity-discharge ignition system is employed, will turn the engine at a rate to provide firing of the spark plugs. However, in cold weather, the rate of turning of the engine crankshaft is reduced so that the pulses produced in the magneto-output winding 325 may not be sufficient to provide proper firing of the spark plugs and the trigger pulses produced in the trigger coils may not be sufficient to properly actuate the silicon-controlled rectifiers. In order to provide easy starting of the engine and good operation up to normal engine operating speeds, booster circuit 300 is preferably employed, the booster circuit operating independent of engine speed to provide increased energy in the ignition system to produce adequate ignition even under unfavorable conditions.

The booster circuit 300 shown in FIG. 5 has some parts similar to those of the booster circuit of FIG. 3 but is provided with further circuitry to provide additional features. In the present instance, the booster circuit comprises a battery 480 which has its negative terminal connected to the common terminal of double-throw single-pole switch 482 and its positive terminal connected to the common terminal of double-pole single-throw switch 484. The switches 482 and 484 are mechanically ganged to operate together so that they connect the battery in the booster circuit, either as shown by the solid line positions of the switches or the dotted line positions of the switches in FIG. 5. In the solid line position of switch 482, the negative terminal of the battery is connected to one terminal 486a of switch 486, the other terminal 486b of switch 486 being electrically connected to a transformer oscillator circuit, generally designated 488. The transformer oscillator circuit is adapted to provide high-voltage pulses through diodes 490 and 492 to charge capacitors 330 and 328, respectively, of the ignition system. More specifically, diodes 490 and 492 are connected in parallel to the output of the transformer oscillator circuit to conduct positive pulses of voltage to the capacitors 330 and 328 in the ignition system circuit through lines 494 and 496, respectively.

The transformer oscillator circuit 488 comprises a transformer, generally designated 500, having a primary winding 502 and two secondary windings 504 and 506. The primary winding 502 has one end connected to terminal 486b of switch 486 and its other end connected to the collector of transistor 508, which has its emitter connected to electrical ground. Also, there is connected between terminal 486b of switch 486 and electrical ground, a voltage divider circuit comprising resistors 510 and 512. One end of secondary winding 504 is connected between resistors 510 and 512, and the other end of secondary winding 504 is connected to the base of transistor 508. Secondary winding 506 of the transformer has one end connected to electrical ground and its other end connected to the anodes of diodes 490 and 492, as shown in FIG. 5.

The operation of the transformer oscillator 488 is such that, when switch 486 is closed and switches 482 and 484 are connected as shown in solid lines in FIG. 5, transistor 508 is initially biased to its conductive state by the potential applied to its base through resistor 510 and secondary winding 504. With the transistor in its conductive state, current flows through primary winding 502 and the transistor and results in voltage pulses being induced in secondary windings 504 and 506. The voltage pulse induced in secondary winding 504 causes the transistor to become nonconductive. The high-voltage positive pulse induced in secondary winding 506 passes through diodes 490 and 492 and charges capacitors 330 and 328, respectively. The transformer 500 steps up the battery voltage to a desired level for charging capacitors 328 and 330. When the voltage induced in secondary winding 504 by primary winding 502 drops below the potential required to bias the transistor to its nonconductive state, then the transistor returns to its conductive state to permit current to flow through primary winding 502 and the transistor, repeating the cycle to produce another high-voltage pulse in secondary winding 506 for charging the capacitors 328 and 330 to a desired level.

The booster circuit 300 provides pulses supplied through lines 494 and 496 to charge capacitors 328 and 330 to a sufficient energy level to assure reliability of operation and optimum efficiency of the engine during starting and at idling or low operating speeds of the engine. The booster circuit thus provides pulses of energy, in this case voltage pulses, having sufficient potential to adequately charge the capacitors, independent of the operating condition of the engine, to assure reliable operation of the engine up to a desired or predetermined engine speed, at which time the booster circuit can be deenergized by opening switch 486 in the booster circuit.

In accordance with a further feature of the present booster circuit of FIG. 5, means is provided by the booster circuit for increasing the energy in the trigger pulse generator, which generates the pulses in the trigger coils 340a-340l to actuate the associated silicon-controlled rectifiers to their conductive state for permitting discharge of the associated capacitor therethrough to fire the associated spark plug. Thus, the booster circuit provides means for increasing the energy in the trigger pulse generator to assure the generation of a reliable trigger signal in the trigger coils for efficient and reliable operation of the ignition system.

The preferred means in the booster circuit for providing additional energy in the trigger pulse generator comprises a coupling or rectifier circuit, generally designated 520, and a booster coil 522 connected to the output of the coupling circuit. The coupling circuit 520 comprises a diode 524 having its anode connected to the output of secondary winding 506 of transformer 500 and having its cathode connected to the anode of silicon controlled rectifier 526, which has its cathode connected to output line 528. Output line 528 is connected to one side of booster coil 522, which has its other side connected to electrical ground. The pulse-forming circuit 520 also includes a capacitor 530 which has one plate connected to the cathode of diode 524 and its other plate connected to electrical ground. Control terminal 526a of silicon-controlled rectifier 526, which is responsive to a control signal for actuating the rectifier to its conductive state, is connected through biasing resistor 532 and zener diode 534 to the cathode of diode 524 and capacitor 530, as shown in FIG. 5. The zener diode 534 is so poled that it is normally nonconductive until capacitor 530 is charged to a predetermined potential by the output of transformer oscillator 488. Preferably, a resistor 531 is connected between the control terminal and cathode of silicon-controlled rectifier 526. Resistor 531 provides a desensitizing resistance to make the rectifier less susceptible to transient voltages which might turn on the silicon-controlled rectifier at undesired times.

In operation of the coupling circuit 520 and booster coil 522, the pulses which are generated in secondary winding 506 are conducted through diode 524 to charge capacitor 530. When the voltage stored in capacitor 530 has reached a predetermined value sufficient to cause breakdown of zener diode 534 rendering it conductive, the control terminal 526a of silicon-controlled rectifier 526 will have a positive potential applied thereto from capacitor 530 so that rectifier 526 is actuated to its conductive state to pass current. When silicon-controlled rectifier 526 is actuated to its conductive state, capacitor 530 is suddenly discharged through the silicon-controlled rectifier and booster coil 522. The pulse supplied to booster coil 522 creates a magnetic flux to provide additional energy in the trigger pulse generator, as will be explained more fully hereinafter. Capacitor 530 charges in response to positive pulses generated in secondary winding 506 of transformer 500 and discharges when a particular level of charge is reached determined by zener diode 534.

The booster coil 522 in FIG. 5 is shown in detail in the trigger pulse generator 400 of FIG. 7. In the trigger pulse generator of FIG. 7, booster coil 522 is wound on a bobbin 550 of nonmagnetic material, which encircles the permanent magnet 428 and is supported by apertured plate 414. The booster coil 522 is positioned between apertured plate 414 and rotor arm 422 and is wound on the bobbin in a direction such that the pulses from the pulse-forming circuit applied to the booster coil create a magnetic flux, which increases or boosts the magnetic flux of permanent magnet 428 passing through rotor arm 422 for inducing pulses in the trigger coils. As indicated in FIG. 7, one end of booster coil 522 is grounded and the other end is connected by line 528 to pulse-forming circuit 520, as schematically shown in FIG. 5. When the engine is started and the rotor arm 422 is rotated, pulses are preferably applied to booster coil 522 from the booster circuit to increase the magnetic flux from the permanent magnet passing through rotor arm 422, thereby increasing the magnetic energy-inducing pulses in the trigger coils.

In this arrangement, the magnitude of the control signals generated in the trigger coils is increased to assure that the associated silicon-controlled rectifier is reliably triggered for having the main storage capacitors of the ignition system discharged to fire the spark plugs in synchronism with engine operation. Thus, the booster coil provides pulses of energy to the magnetic circuit of the trigger pulse generator for increasing the magnetic energy in the magnetic circuit for assuring the production of a suitable signal by the appropriate trigger coil applied to the control terminal of its associated switch means when the engine is started and during engine operation to a desired speed. The transformer oscillator described in FIG. 5 oscillates at a frequency on the order of 3,000 cycles per second to provide the desired frequency of output pulses from the pulse-forming circuit applied to the booster coil.

It should be understood that the booster coil associated with the trigger pulse generator could be positioned in the generator at a number of different locations, as long as the magnetic flux created by current in the booster coil passes through the magnetic circuit of the trigger pulse generator to increase the magnetic flux created by the permanent magnet. Of course, in other arrangements of trigger pulse generators, the booster coil would be positioned differently but would perform the same function of providing additional flux in the magnetic circuit of the generator to increase the overall magnetic flux in the magnetic circuit.

In accordance with a further feature of the present invention, means is provided for charging the battery of the booster circuit from the ignition system, once the engine is operating satisfactorily within its range of normal operating speeds. More specifically, the charging circuit for the battery is provided by having terminal 484b of switch 484 connected by line 560 to line 496, which is connected to capacitor 328 and one side of output winding 325 through diode 354. The charging circuit is completed by having terminal 482b of switch 482 connected to electrical ground by way of the series circuit provided by diode 562, resistor 564 and zener diode 566. When the mechanically ganged switches 482 and 484 are placed in the dotted line, alternative positions of the poles as shown in FIG. 5, the charging circuit is completed for charging battery 480. In this arrangement, the pulses from the ignition system are supplied to the battery for charging the battery. The charging circuit for the battery is, of course, optional. The battery might be charged from any external DC source or a recharging circuit may be completely omitted. Further, the direct current source needed for the booster circuit could be provided by some other means than a battery, such as, a rectified AC source of power.

It should also be appreciated that it may not be necessary to have the booster circuit both charge the main storage capacitor of the ignition system and provide additional energy to the trigger pulse generator, as described in regard to FIG. 5. These features of the booster circuit can both be provided or they may be employed independently as required by the particular application and operation of the ignition system and engine. Furthermore, after the engine has been started and is operating as desired, the booster circuit can be deenergized by opening switch 486 or by moving the poles of switches 482 and 484 to the alternative position shown in FIG. 5 for charging the battery. Moreover, after the engine has been started and is operating as desired, the booster circuit can be physically removed by disconnecting the booster circuit from lines 494, 496 and 528 and the booster circuit can be employed in another location with another ignition system, as desired.

There is shown in FIG. 8 a schematic circuit diagram illustrating another overall ignition system with which a booster circuit in accordance with the present invention is employed. In this example of FIG. 8, the booster circuit employed is preferably generally the same as the booster circuit shown in FIG. 5 so that the booster circuit in FIG. 8 is shown in block diagram form. In FIG. 8, parts of the booster circuit, similar to those of the booster circuit of FIG. 5, are identified by the same number designators with the addition of primes thereto. The only difference between the booster circuit 300' employed in FIG. 8 and the booster circuit 300 of FIG. 5 is that the battery charging portion of the booster circuit of FIG. 5 is not needed in the FIG. 8 arrangement and that diode 492 and line 496 of FIG. 5 are not needed in the FIG. 8 arrangement since only one line (494' in FIG. 8) connecting the output of the transformer oscillator to the ignition system is required, as shown.

The overall ignition system represented in FIG. 8 is of the type shown and described in detail in U.S. Pat. No. 3,034,018 of M. I. Rosenberg, entitled "Transistorized Breakerless Ignition System," and of common assignee herewith. To provide an understanding of the ignition system of FIG. 8, the following brief description is set forth. The ignition system comprises a magnetic pulse generator, generally designated 600, having a rotor 602, which has a face-polarized permanent magnet positioned between plates 604 and 606. Each of the plates provide pole pieces having radially extending portions which provide pole faces of one polarity around the rotor, the pole faces of pole piece 604 being staggered around the rotor with the pole faces of pole piece 606 to provide pole faces of alternate polarity around the rotor, as shown in FIG. 8. The pole faces of alternate polarity are located in pairs around the rotor, one pair being provided for each cylinder of the engine.

The rotor of the pulse generator has associated therewith a distributor, generally designated 610, which has eight output terminals, designated 612a-612h, one for each cylinder of the engine. Each output terminal of the distributor is connected to one of the eight spark plugs 614-628. Distributor rotor arm 630 alternately contacts each of the output terminals to conduct pulses to the spark plugs to fire the spark plugs in synchronism with engine operation.

Adjacent the periphery of the magnetic rotor 602 there is provided a control coil 632 wound on the center leg of a generally E-shaped stator member 634 fixedly positioned in close proximity to the projections providing the pole faces of the rotor to complete a magnetic circuit for each of the pairs of alternate polarity poles once each revolution of the rotor. The spacing of the legs of the generally E-shaped stator generally corresponds to the spacing between each of the pairs of pole faces provided by the rotor.

The distributor contact arm which rotates with the rotor structure of magnetic pulse generator 600 is connected to secondary winding 636 of voltage step-up transformer 638, the primary winding 640 of the transformer being connected to a switching circuit, generally designated 642.

The ignition system further includes a source of voltage, which may be provided by a DC battery 644 having its negative terminal connected to electrical ground through ignition switch 646. The positive terminal of battery 644 is connected to the anode of diode 648 which has its cathode connected to the switching circuit 642.

The switching circuit 642 comprises a power transistor 650, which has its emitter connected to the cathode of diode 652, the anode of diode 652 being connected to the cathode of diode 648. The collector of transistor 650 is connected to primary winding 640 of voltage step-up transformer 638. Biasing resistor 654 is connected between the anode of diode 652 and the base of transistor 650 to stabilize the power transistor. The base of transistor 650 is connected to the emitter of triggering transistor 656, which has its collector connected to electrical ground. The base of triggering transistor 656 is connected to one side of control coil 632, the other side of control coil 632 being connected to the emitter of triggering transistor 656. A zener diode 658 is connected between the base and emitter of transistor 656.

In operation of the ignition system of FIG. 8, when ignition switch 646 is closed, the starting motor for the engine, with which the ignition system is employed, turns the engine crankshaft, which in turn rotates the pulse generator rotor 602. The rotating trigger rotor 602 induces a pulsating voltage in control coil 632. The voltage induced in control coil 632 causes trigger transistor 656 to rapidly switch to its conductive state, which, in turn, causes power transistor 650 to rapidly switch to its conductive state. With transistor 650 in its conductive state, a current transient is supplied to the primary winding 640 of transformer 638 from battery 644, the current transient causing a voltage transient in the primary of the transformer which induces a high voltage in secondary winding 636 which is conducted through distributor rotor arm 630 to the appropriate one of the spark plugs in synchronism with engine operation.

Upon starting the engine and at slow engine speeds, the ignition system of FIG. 8 may not initially provide adequate energy to fire the spark plugs under unfavorable conditions. In addition, the voltage generated in control coil 632 by the distributor rotor, which is geared to the engine crankshaft, may not be sufficient to reliably actuate the switching circuit. In order to provide sufficient energy in the ignition system of FIG. 8 for reliable operation upon starting the engine and at low engine speeds, the booster circuit 300' is preferably employed. As shown in FIG. 8, output line 494' from booster circuit 300' is connected in the ignition system between the cathode of diode 648 and the anode of diode 652. Diode 648 prevents the battery from absorbing the pulses of energy supplied from the booster circuit for firing the spark plug.

In this arrangement, when the switching circuit is conductive, that is transistor 650 is conductive, the pulses from the booster circuit are supplied to the primary winding of transformer 638 and to the spark plug of the engine through distributor rotor arm 630 for firing the spark plug. Since the output of the booster circuit 300' provides a series of high-frequency pulses, more than one pulse will be supplied to the spark plug during each firing interval so that a series of sparks is obtained at the spark plug for having better and reliable combustion in the engine cylinders for starting and operating the engine.

Further, in accordance with the present booster circuit, output line 528' from the booster circuit, which is connected in the booster circuit to the output of the coupling circuit as described in regard to the booster circuit of FIG. 5, is connected to booster coil 522' wound on a bobbin supported by rotor 602, as shown in FIG. 8. More specifically, line 528' is connected to an insulated conductive ring 670 through an appropriate brush and ring 670 has one end of coil 522' connected thereto. Ring 670 is supported by plate 604. The other side of booster coil 522' is connected to insulated ring 672, which is supported by plate 604 and is connected through an appropriate brush to electrical ground as indicated in FIG. 8. Booster coil 522' is wound on a bobbin and positioned between the disc-shaped permanent magnet of the rotor and plate 604. The pulses from the booster circuit supplied to the booster coil, which is wound in an appropriate direction, produces in the booster coil a magnet flux to increase or boost the magnetic flux in the magnetic circuit of the pulse-generating rotor, thereby increasing the magnitude of the pulses induced in control coil 632 to assure switching of the switching circuit 642. Hence, booster coil 522' serves to improve the trigger signal induced in the control coil to assure reliable operation of the ignition system at desired predetermined engine speeds.

As indicated in regard to FIG. 3a, since the ignition system of FIG. 8 employs a battery, the battery 644 may be connected to the booster circuit in a manner similar to the battery in FIG. 3a for providing the power to the booster circuit, so that a separate power source would not be required in the booster circuit.

It should be appreciated that the booster circuit of the present invention can be employed with a wide variety of ignition systems to assure reliable operation of the ignition system. The present booster circuit can be employed to provide multiple sparks for firing the spark plugs of the engine cylinders and can boost the energy of a capacity-discharge ignition system for adequate firing of the engine spark plugs. Furthermore, the present invention can be employed to increase the energy in the magnetic circuit of a trigger pulse generator in ignition systems which employ such an arrangement. Furthermore, the booster circuit can be provided with means for permitting charging of the power source in the booster circuit, as illustrated in regard to the capacity-discharge ignition system of FIG. 5. The present booster circuit eliminates the conventional vibrator apparatus which is employed in previous booster systems to increase the energy in the ignition system. The booster circuit of the present invention is compact and reliable and employs a few simple circuit components providing an inexpensive system capable of trouble-free operation.

While the present invention has been described with particular reference to specific embodiments thereof in the interest of complete definiteness, it will be understood that it may be embodied in a large variety of forms diverse from those specifically shown and described without departing from the scope and spirit of the invention as defined by the appended claims.

Claims

We claim:

1. In a booster circuit for use with an ignition system for an internal combustion engine, the ignition system including a voltage source, ignition means for igniting fuel in the engine in synchronism with engine operation, controllable switch means for selectively completing a circuit with the voltage source and the ignition means to ignite fuel in the engine, the switch means having a control terminal responsive to a control signal to actuate the switch means to complete the circuit, and a trigger pulse generator for generating a control signal applied to the control terminal for actuating the switch means, the combination therewith of: a booster power circuit having electronic circuitry including at least two outputs for providing booster energy at the outputs, first means for connecting one of the outputs of the booster circuit power with the circuit completed by the controllable switch means to assure producing of a suitable voltage applied to the ignition means to ignite fuel in the engine, and second means for connecting another output of the booster power circuit with the trigger pulse generator to provide an increased intensity control signal to assure actuation of the switch means.

2. The booster circuit of claim 1 in which the trigger pulse generator includes a magnetogenerator having a magnetic circuit, and the second means for connecting another output of the booster power circuit with the trigger pulse generator includes a booster coil connected in the magnetogenerator to which the booster energy is applied for increasing the magnetic energy in the magnetic circuit to provide an increased intensity control signal.

3. The booster circuit of claim 2 in which the first means connects the booster power circuit with the circuit of the voltage source to increase the electrical energy from the voltage source applied to the ignition means.

4. The booster circuit of claim 3 in which the booster power circuit is connected with the voltage source and the trigger pulse generator upon starting the engine.

5. The booster circuit of claim 1 in which the voltage source includes capacitive means and a magnetogenerator for charging the capacitive means, the switch means completing the circuit with the capacitive means and the ignition means for discharging the capacitive means through the ignition means, and the first means connects the booster power circuit to the circuit to charge the capacitive means.

6. The booster circuit of claim 5 in which the trigger pulse generator includes a magnetogenerator having a magnetic circuit, and the second means for connecting another output of the booster power circuit with the trigger pulse generator includes a booster coil in the trigger pulse generator to which the booster energy is applied for increasing the magnetic energy in the magnetic circuit to provide an increased intensity control signal by the trigger pulse generator.

7. The booster circuit of claim 1 in which the second means connects the booster power circuit with the trigger pulse generator by circuitry in the trigger pulse generator which increases the intensity of the control signal to actuate the switch means.

8. The booster circuit of claim 7 in which the circuitry in the trigger pulse generator includes a booster coil responsive to the booster energy from the booster power circuit.

9. The booster circuit of claim 1 in which the trigger pulse generator includes a magnetic circuit with a magnet pole and a conductor rotated past each other in synchronism with engine operation to generate the control signal in the conductor, and the second means for connecting another output of the booster power circuit with the trigger pulse generator includes a booster coil which is interposed in the magnetic circuit of the trigger pulse generator for increasing the energy in the magnetic circuit to provide an increased intensity control signal in the conductor to actuate the switch means.

10. The booster circuit of claim 9 in which the voltage source comprises a magnetogenerator and the first means connects one of the outputs of the booster power circuit to the output of the magnetogenerator.

11. The booster circuit of claim 9 in which the magnet pole is rotated relative to the conductor, and the booster coil is positioned coaxial with the axis of rotation of the magnet pole.

12. The booster circuit of claim 9 in which the magnet pole is supported by and rotates with a shaft, and the booster coil encircles the shaft and creates a magnetic flux which increases the magnetic flux of the magnet pole.

13. The booster circuit of claim 12 in which the booster coil is supported by a nonrotatable structure.

14. The booster circuit of claim 1 in which the booster power circuit includes a source of voltage, oscillator means responsive to the source of voltage for generating a series of pulses and rectifier means for providing output pulses of one polarity.

15. The booster circuit of claim 14 in which the oscillator means comprises a blocking oscillator.

16. The booster circuit of claim 14 in which the rectifier means includes an electronic switch having a control element responsive to a predetermined voltage and means connected in the circuit of the control element for permitting passage of current to the control element in response to a voltage in excess of a predetermined level, and energy storage means responsive to the output of the oscillator means for charging to a voltage in excess of the predetermined level applied to the means connected in the circuit of the control element for actuating the electronic switch by the predetermined voltage to permit discharge of the energy storage means through the electronic switch to provide pulses of booster energy.

17. In a booster circuit for use with an ignition system for an internal combustion engine, the ignition system including a voltage source, ignition means for igniting fuel in the engine in synchronism with engine operation, controllable switch means for selectively completing a circuit with the voltage source and the ignition means to ignite fuel in the engine, the switch means having a control terminal responsive to a control signal to actuate the switch means to complete the circuit, and a trigger pulse generator for generating a control signal applied to the control terminals for actuating the switch means and including a magnetic circuit with a magnet pole and a conductor rotated past each other in synchronism with engine operation to generate the control signal in the conductor, the combination therewith of: a booster power circuit having electronic circuitry including at least one output for providing booster energy at the output, and means for connecting the output with the trigger pulse generator to increase the intensity of the control signal to assure actuation of the switch means, the means for connecting the output of the booster power circuit with the trigger pulse generator including a booster coil which is interposed in the magnetic circuit of the trigger pulse generator for increasing the energy in the magnetic circuit to provide an increased intensity control signal in the conductor to actuate the switch means.

18. The booster circuit of claim 17 in which the magnet pole is rotated relative to the conductor, and the booster coil is positioned coaxial with the axis of rotation of the magnet pole.

19. The booster circuit of claim 17 in which the magnet pole is supported by and rotates with a shaft, and the booster coil encircles the shaft and creates a magnetic flux which increases the magnetic flux of the magnet pole.