SE445847B - PROCEDURE FOR ELECTRONIC IGNITION SYSTEM OF MULTIPLE-SPARK TYPE IMPROVE THE IGNITION EQUIPMENT FOR ASTAD COMMANDING OF THE PROCEDURE - Google Patents

Description

In this way, with the method and the device according to the invention, spark energy can be applied many times higher than with ordinary "mechanical" ignition with a switch tip. This gives a very significant improvement in the engine's willingness to start in difficult conditions, whereby the need for shock is reduced or disappears completely. Furthermore, fuel consumption is reduced through the warmer, more energy-rich sparks and wear on the starter motor, battery and spark plug, as well as, where applicable, switch tip, is reduced.

Particularly in the case of "exhaust-purified" cars, the method and device according to the invention are attractive, since in relatively low revs and cold engines, relatively lean fuel mixtures are still sought.

The invention is useful in ignition systems with contactless, electronic sensors as well as in conventional "mechanical" ignition systems with switch tips.

The device according to the invention is suitably designed so that during the starting process a spark burst is generated, the first spark being longer and more powerful than the subsequent ones and coming at exactly the right ignition angle, while the other sparks come at a fast pace while the piston moves the first fifth of its stroke down. At idle, a triple spark is generated that provides smooth running and no risk of theft, even though the fuel mixture is often uneven. At high engine speeds, the turbulence is so strong that the fuel mixture becomes fairly homogeneous, which is why a single spark, as with a normal ignition system, is sufficient.

The multiple ignition at start-up normally automatically changes to triple ignition at idle and single ignition at high revs, as the switch tip or electronic contactor opens and closes faster at higher engine speeds so that fewer and fewer pulses or sparks can be accommodated per ignition period with similar engine speeds and constant spark frequency.

The device according to the invention can be switchable between a multiple spark mode, a single spark mode (may be desirable in areas with difficult radio reception conditions, and during ignition setting), and to, where applicable, "mechanical" ignition in an emergency if the transistor ignition should break .

An exemplary embodiment of the device according to the invention applied to an ignition system with switch tip will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a diagram of an electronic ignition system with the device according to the invention, Figs. 2 and 3 8305584 -0 diagram for illustration of the function of the system and fig. 4 a diagram for illustration of a possible mode of operation of the logic circuit at the device according to the invention.

The device according to the invention is shown in Fig. 1 built up of three parts, namely a part A for producing the different durations of the multiple sparks, the switch tip part B and a power output stage E.

For a description of the operation of the device, reference is made to Figs. 2 and 3.

The circle in Fig. 2 illustrates the crankshaft revolution of the engine, where a point on the circle in height corresponds to the position of the piston in the cylinder bore (sine curve).

The cam that controls the switch tip BR, see Fig. 1, is so adapted that the switch tip BR is closed below typically 58 ° (dwell number is 58 °) and open below 90 - 58 = 32 °. The crankshaft moves twice as fast as the cam curve and the switch tip BR is closed during the time corresponding to the circular arc x in Fig. 2, which thus occupies an arc of 2. 58 = 1160. During this period, magnetic energy is stored in the ignition coil 2.

At point y in Fig. 2, the switch tip BR opens, igniting the spark and the switch tip BR is open for a time corresponding to the arc z in Fig. 2. The point y is on a suitable ignition, e.g. 10 ° at idle.

It takes a relatively long time to charge full magnetic energy in the ignition coil 2, so the period x should be relatively long. At point y, maximum energy is stored in the ignition coil 2 and at this ignition angle the ignition is desired. However, the gas-fuel mixture is often inhomogeneous and when the ignition spark hits a layer with an inappropriate mixing ratio, the combustion is absent, which is a common phenomenon in today's cars and contributes to harmful emissions and gives higher fuel consumption. It is therefore a desire of the present invention to allow the high energy first spark to burn for as long as possible. The duration can be of the order of> 1 ms and the magnitude of the spark current becomes at the first moment of the order of 50 mA, whereupon the current decreases substantially linearly with time, cf. also Fig. 3.

Should this powerful, first ignition spark fail to ignite the gas-fuel mixture, a number of subsequent ignition sparks are generated during period z, which always leads to safe ignition of the gas fuel mixture. This corresponds to the time period during which the switch tip BR is open, see Fig. 3.

If, after the powerful, first ignition spark, the ignition coil 2 is to be charged to maximum energy, this takes so long that no additional spark has time to be generated during period z. If, on the other hand, one tries to extract a very large number of sparks during this period z , each spark becomes so low in energy that it cannot ignite the gas fuel mixture. Between these extreme cases, however, there is an optimal spark frequency which, under prevailing conditions, provides maximum ignition energy to the spark plug. The optimal way to drive the ignition coil means that the burning time of the subsequent sparks is made shorter to enable longer magnetic charging of the ignition coil 2 between each spark, see Fig. 3. The time it takes to charge magnetic energy in the ignition coil 2 depends on the driving voltage and the primary inductance. There are special high-speed sports coils with a very fast charging time, but the principle described above also applies to these, whereby, however, the subsequent sparks can be emitted with a higher frequency.

In the case of previously known so-called SCR (Silicon controlled rectifier) or thyristor ignition systems of the multiple spark type, the energy is stored in a capacitor, which with SCR is connected in parallel across the ignition coil, the ignition coil only serving as a transformer. In this way, however, sparks of relatively short duration can only be obtained, as a result of which the combustion often seems insufficient with high emissions as a result. In the present invention, the energy in the form of magnetic energy is stored in the core of the ignition coil, whereby the duration of each spark becomes a factor of 10 longer. The magnetic ignition principle is now increasingly prescribed in professional circuits.

The ignition coil 2 is driven by the transistor TR3, which in turn is controlled from a logic circuit 4.

The logic circuit 4 outputs a pulse train through the resistor R6 and the transistor TR1 to the base of the transistor TR3 in such a way that the transistor TR3 is controlled in the desired manner, i.e. it opens during a series of intervals, the length t2 of the first interval being greater than the subsequent intervals t4, during the period when the switch tip BR is open, see Fig. 3. During each opening interval of the transistor TR3, an ignition spark is generated.

The logic circuit 4 for controlling the transistor TR3 can be a customized monolithic circuit with, for example, the following function.

When the switch tip BR is opened and the first spark is generated, a voltage U4 arises across the capacitor C4 which rises from an output level U0 during the duration of the spark by charging the capacitor C4, see below. During the rising part of the voltage U4, the logic circuit emits at its output 6 an output pulse with the voltage Uoué. When U4 reaches a predetermined threshold value U1, the logic circuit is switched so that the output voltage Uout goes to 0.

After the U4 has reached the level U1, U4 begins to fall and when it reaches a second, predetermined threshold value U2, the logic circuit switches again so that the output 6 becomes high, whereupon the input voltage starts to grow again due to charging of the capacitor C4, whereupon its switch tip BR closes. 8303584-0 Because C4 starts from an output level U0 that is lower than the start level U2 for the subsequent pulses, the first pulse in the burst of pulses becomes longer than the subsequent ones. The pulse times are determined by C4 and an internal current generator in the monolith circuit 4 and by suitable dimensioning of time constants the distance t3 between the pulses can be made considerably longer than the pulses themselves t4 to enable optimal re-storage of energy in the ignition coil 2.

The value of the capacitor CS determines the longest time that multiple sparks can be emitted at a statically open circuit breaker. In this case, you can maximize the number of sparks in a spark burst to approximately 30 pcs. This limitation occurs when the engine is stationary with the ignition on, or when the engine is moving very slowly during start-up. This function is important, because otherwise the motor could run completely without bmmmmß (mæwm fl L The pulses from the logic circuit are routed, as mentioned above, to the base of the transistor TR3 for triggering it, the transistor TR1 serving to amplify the pulses from the logic circuit 4 R7 serves as current limiter in the event of a short circuit in the ignition coil 2.

The transistor TR3 serves as a very fast switch and the ignition capacitor C6 can therefore be made considerably smaller than with a "mechanical" ignition system. The capacitance of the capacitor C6 can be reduced by typically a factor of 10, which means that this component "steals" 10 times less energy from the primary pulse, which gives higher voltage on the ignition spark and more energy-rich spark.

In the present invention, the process can be suitably adapted so that the first spark becomes stronger than with "mechanical" ignition, while the subsequent multiple sparks become as strong as with a "mechanical" ignition.

When an ignition spark occurs, a voltage spike is obtained across the transistor TR3.

With a spark voltage of 30kV and a turnover in the ignition coil 2 of 1: 100, this voltage spike is about 300V. This pulse is conducted through the diode D1 and a direct voltage of the same magnitude will be stored in the capacitor C1, which is thereby charged by the multiple sparks to about 300 V.

In order not to load the ignition process, the capacitor C1 is connected across the switch tip BR via a large resistor R1.

Via the resistors R1 and R2, the capacitor C2 is charged up to the same voltage as the capacitor C1, and when the switch tip BR is closed, the capacitor C2 is rapidly discharged through the resistor R2, which has a low value. This results in a short current surge of the order of 30A, which penetrates oxide and dirt on the contact surfaces of the switch tip and provides a microscopic welding point. The capacitor C1 will then remain at a substantially constant level (300 V) due to the high-ohmic resistance R1. 8303584-0 Examples of suitable component values are Cl = 1 F Rl = 680 kohm R2 = 10 ohms After the switch tip BR has been effectively closed, a relatively large current from +12 V is supplied through the resistor R3 and the diode DZ and through the switch tip BR to ground.

Thus, by applying to the switch tip BR a high voltage of about 300 V and a high current of 30 A in an initial current surge and then 0.5 A, a safe contact function is obtained which can compete with electronic sensors.

The advantages of a mechanical contact are 1) low cost, 2) simple construction and high operational reliability, 3) insensitivity to high temperatures and 4) possibility of switching the ignition system to conventional "mechanical" ignition in the presence of fa1 in the electronics so that one for own machine can go to a workshop.

The ignition system, as described above, can be easily arranged switchable between a multi-ignition mode, a single-spark mode and ordinary "mechanical" ignition.

Claims (9)

8303584-0 Patent claims. A method for improving the ignition in a multiple spark type electronic ignition system, especially in difficult operating conditions, wherein the energy required for the spark generation is stored as magnetic energy in the core of the ignition coil (2), characterized in that the first spark is given longer duration and made stronger ( higher current) than subsequent sparks in each burst of sparks during an ignition period. 2. A method according to claim 1, characterized in that the length and mutual distance of said subsequent sparks are adapted to the speeds of the storage of the stored magnetic energy during the sparks and re-storage between them, so that total maximum ignition energy is supplied to the spark plug. Device in electronic ignition system for producing multiple sparks of different duration of magnetic energy stored in the magnetic core of the ignition coil (2), characterized in that a logic circuit (4) is arranged to control a transistor (TR3) for on and off at predetermined times, which transistor is connected in series with the primary winding of the ignition coil (2), whereby magnetic energy stored in the ignition coil magnetic core through the secondary winding secondary winding generates a spark during each open interval of the transistor, and that the logic circuit is arranged to keep the transistor open for a first period. interval (t2), which is longer than subsequent open intervals (t4), and the distance (t3) between said subsequent open intervals of the transistor is less than the time required to re-store in the ignition coil magnetic core all the spark energy discharged during the first open interval . Device according to claim 3, characterized in that the logic circuit (4) is arranged to generate an output pulse train (Uout) during each ignition period with the first pulse (t2) in the train longer than the subsequent ones (t4), which output pulse train is input to the base to the transistor (TR3) connected in series with the primary winding of the ignition coil (2), so that it will open during the pulses from the logic circuit. Device according to claim 3 or 4, characterized in that the logic circuit (4) is arranged to emit an output pulse during rising parts of a voltage (U4), and that said voltage is equal to a basic level (Uo) outside the ignition period and is eliminated. from this basic level (UO) at the beginning GV a tä fl dP @ Yl0d and then varies between two levels (UI) and (U2) 11115 the end of the ignition period (whereby U1> U2> UU) Device according to claim 3 or 4, characterized in that the logic circuit (4) has an overall time function which limits the number of sparks in a spark burst to an appropriate number, for example 30 pcs. Device according to any one of claims 3 to 6, characterized in that the logic circuit is a monolithic circuit. Device according to one of Claims 3 to 7, in which the ignition system is of a mechanical type with a switch tip (BR), characterized in that the input of the logic circuit (4) is indicated above the switch tip (BR), the ignition period beginning and s the opening and closing of the switch tip, respectively. Device according to any one of claims 3 - 8, characterized in that means (TR2; R7) are arranged to protect the transistor {TR3) connected in series with the ignition coil (2) in the event of a short circuit in the ignition coil.