DE3925224A1 - Ignition method for IC engine esp. in lawn-mower or chain saw - Google Patents

Abstract

The energy storage element (C1) is discharged by a switching element (Thy) across the prim. coil (L2) of an ignition transformer (L2,L3). The switching element (Thy) is operated, if the rising flank of the first half wave (I) within each revolution (T) reaches a trigger threshold. At least one of the half waves following the first half wave (I) is blocked in response to the operation of the switching element (Thy). A flat is provided which is set with the last half wave within each revolution, such that it signals the release of the ignition (9), and the flag is reset with the smallest second half wave of each revolution (T), for the purpose of blocking the ignition (9).

Description

The invention relates to an ignition method for internal combustion engines machines, especially in lawn mowers or chainsaws which a magnet generator for each machine revolution one Most of them are continuous and alternating polar induced voltage half-waves, by means of which a Energy storage element charged and by a switching element discharged through the primary coil of an ignition transformer becomes. The invention further relates to a capacitor ignition System for internal combustion engines, with a speed-dependent AC voltage inducing magnetic generator and one the alternating voltage trigger device for Actuate the one via the primary coil of a Ignition transformer discharging switch; this arrangement is particularly to carry out the aforementioned procedure rens designed.

In known ignition systems such as the type mentioned (cf. US Pat. No. 31,837) is the inner leg of a three leg, ferromagnetic iron core from a coil surrounding arrangement. It creates one with the rotating one Machine shaft coupled magnet wheel, which in peripheral Place a tangentially aligned permanent magnet indicates a sequence of alternating voltage half-waves. The former are used to charge an energy storage device used and only the last half-wave is used for Activation of the capacitor via the ignition transformer ending thyristor. In practice, however, one poses found that with this approach with increasing rotation  Pay the ignition later and later regarding the absolute angle position of the magnetic pole wheel is triggered. Explanations for this phenomenon could be found in the eddy current and Hysteresis losses during the previous trigger triggering Magnetic reversal of the iron core and in the stress of the entire ignition system through capacities and Low pass characteristics are.

In contrast, the invention is based on the object minimal effort to advance the ignition range, which increases with increasing speeds. To the solution is used in an ignition process with the aforementioned Features proposed according to the invention that the switching link (always) is actuated when the within each Revolution first induced half-wave a trigger threshold reached.

Basically, with increasing machine speed or Magnetic generator angular velocity the slopes of the induced voltage half-waves getting bigger. During the second, third, fourth etc. half-wave however ma laziness and other dynamic inadequacies ten of the overall system, including due to the above Circumstances (hysteresis, eddy current losses, capacities, Low pass behavior), noticeable; in any case, one can increasing widening of the half-waves mentioned the first half-wave occurring within one revolution observe. Nevertheless, so far this has always been timed stretched half-waves triggered the ignition because before the first half-wave for charging the ignition capacitor has been serviced and exploited. In contrast, according to the  Invention followed the unorthodox path, like the one with ver every first half-wave for ignition triggering regardless of the state of charge of the ignition capacitor tors. As a result, at the first machine revolution no ignition triggered due to lack of energy in the capacitor. Only with the first half-wave induction within the two th revolution of the machine, the switching element becomes a discharge tion of the energy storage element, which previously was charged by the half-waves of the first revolution. This process is repeated for the further revolutions corresponding.

The rising part or the is expediently rising edge of the first half wave to actuate the Switching element and used for ignition. In further training of the method according to the invention, at least one of the with respect to the first half-wave following half-waves the actuation of the switching element blocked. This allows make sure that triggering of the ignition is no longer once within one machine revolution.

Since magnet generators known per se are usually one Induce sequence of multiple voltage half-waves, that will control problem raised, the triggering the ignition just goes to the first one turn Let the half wave respond. This is fiction countered by providing a flag which set with the last half wave of each revolution is that it signals the release of the ignition. The Flag represents a special sign that the occurrence of a certain event, namely here  End of the last half-wave of the current revolution or the coming first half-wave of the next revolution. This invention training can be particularly easily Implement microprocessors because they are mostly internal Have registers for flag or status bits. With The flag becomes at least an advantage after the ignition is triggered reset with the second half-wave of each revolution, which means locking the ignition. So that is achieved that even then no ignition at the wrong time is triggered when the electromagnetic field of a Sparking the electronically implemented flag in the (Microprocessor) circuit has changed unintentionally.

A capacitor ignition arrangement with the aforementioned Features which are particularly important for the implementation of the explanat tert method is suitable according to the invention with egg nem bistable toggle switch, which due to the last AC half wave within each measurement machine rotation in a state to release the actuator the discharge switch during the first half-wave of next rotation is tilted. Conveniently, the last part of the last half-wave, i.e. its sequence or End used to switch the toggle switch in the release stood to sit.

Digital switchgear like flip-flops are sensitive to electromagnetic interference, which leads to falsification of the switching state can lead. This problem is solved with encountered an embodiment of the invention, according to which the tilt rear derailleur within each revolution due to the second and possibly other subsequent half-waves polarity to its original initial state  is tilted back while pressing the switch locks. Only with the last half-wave of the current revolution hung which polarity opposite polarity has, the toggle switch for ignition release like the set. This prevents misfires.

This periodic reset of the toggle switch is especially advantageous if - after another out education of the invention - this as a single-edge trigger tes toggle flip-flop is formed within each Revolution due to the second and possibly following Half waves of the same polarity is reset, and on whose dynamic clock input is the first and possibly following half-waves of the same opposite polarity act. Toggle flip-flops are known to invert theirs Initial state with every e.g. positive clock edge (cf. Tietze-Schenk "Semiconductor Circuit Technology", 8th edition, Springer-Verlag, p. 237). Is caused by an external fault can cause the flip-flop to tip over this is due to the precautionary reset mentioned, especially if this is before the last half wave of one turn hung occurs, do not result in a misfire.

The toggle switch with a short-circuit Switch connected in such a way that it tipped back Initial state the short circuit switch for suppression controlled by induced trigger half-waves. The resulting avoidance of additional, superfluous ignition, especially when the machine is in one unsuitable rotary position does not need to be explained in more detail. In practice it has proven to be  Proven to be the output of the toggle and a delay element at the input of the short-circuit switch, e.g. interconnect in the form of an RC low pass. There through is lagging the closing or opening of the Short-circuit switch reached to undesirable effects to compensate by delayed, induced half-waves sieren.

For easier realization of the Zündsy according to the invention stems (procedure, arrangement), the Ma gnet generator the lowest possible number of voltages half-wave induced, since only the first voltage anyway half wave is used for ignition triggering and the following Half waves for setting and / or resetting the flag or Toggle switch must be used. It serves that if the system according to the invention with a known Ma gnetgenerator (see. DE-DS 36 08 740) is combined, the a magnetic pole wheel coupled with the machine revolution with tangentially staggered poles and a co-operation with them kende, stationary arranged coil arrangement with ferroma has a magnetic iron core. It is particularly advantageous the idea concretizes that the iron core two has legs facing the pole wheel, of which single Lich one is surrounded by the coil arrangement, which before al lem a charging coil for the ignition capacitor and a trig gerspule for deriving pulses triggering the ignition includes. With this magnet generator training per rotation a first positive, a second negative and one third positive trigger half wave induced. The supra beneficial effect in connection with the previously Outlined system of invention is based on the beginning and that  End of each half-wave cycle with a positive one Half wave: the first half wave can - from the second time Line rotation - always on those still in the iron core build up the residual magnetization after the last one Half wave of the same polarity is still left; this he gives a particularly steep starting flank for the first Half wave, since there is no more magnetic reversal in the iron core necessary is. Practical tests have shown that here with an early adjustment of the ignition between 400 rpm and 12,000 rpm up to 30 ° is possible. The middle, second Half wave of opposite polarity can already be Assign mentioned safety function, namely malfunctions of the flag or toggle switch by resetting it compensate.

Another embodiment of the invention that is related with the minimum number of induced half-waves is an advantage is that the power supply of the toggle switch work of the first and possibly following half-world le depends. With three half-waves per revolution according to the above example, this means that the toggle switch inactivated during most of the machine revolution and consequently do not cause false ignitions can.

Further details, features and advantages of the invention result from the following description of an off exemplary embodiment of the invention and with reference to the drawing. In it show:  

Fig. 1 shows an advantageous embodiment of the invention the magnetic generator partially geschnit tener in axial view,

Fig. 2 shows a circuit implementation of the invention,

Fig. 3 voltage-time diagrams with respect to the magnetic generator induced voltage half-waves and input and output signals of a toggle switch used according to the Invention.

The magnet generator shown in FIG. 1 has a magnet wheel 1 , which is rotated counterclockwise by the machine (not shown) in the direction of rotation 2 . On its outer circumference, a permanent magnet 3 with tangentially offset poles N, S is arranged, which magnetize correspondingly arranged pole pieces. This magnet assembly 3 , 4 is moved during rotation 2 past a ferromagnetic iron core 5 with a U-profile, the first leg 6 of which is surrounded by a coil arrangement L 1 , L 2 , L 3 , L 4 , and the second leg 7 free of coils is. The coil arrangement consists of four coils L 1 to L 4 arranged concentrically with the first leg 6 .

Their function can be seen from the circuit arrangement shown in FIG. 2: The first charging coil L 1 charges an ignition capacitor C 1 via a full-wave rectifier G 1 in, for example, a Graetz circuit. The second coil L 2 or third coil L 3 together form the primary or secondary winding of an ignition transformer 8 . The primary coil L 2 is in series with the ignition capacitor C 1 , when it is discharged via a switch Thy made in the example as a thyristor at the output of the ignition transformer 8, a high-voltage ignition signal 9 is produced. The control or actuation input 10 of the switch Thy is connected to the output of a (indicated by dashed lines) trigger device 11 , which is assigned a fourth coil L 4 as a trigger coil. Furthermore, a protective resistor R 10 and a protective diode D 5 are each connected in parallel to ground at the control input 10 of the switch Thy. In the coil arrangement L 1 to L 4 , continuously coherent and alternately polarized voltage half-waves are generated in a manner known per se, as shown in FIG. 3, diagram a. The trigger coil L 4 is an off switch 12 connected in parallel to ground, which short-circuits the trigger coil L 4 when actuated. Between the trigger coil L 4 and the control input 10 of the switch Thy a only positive half-wave passing diode D 2 and a current limiting resistor R 1 are arranged in series. Between this diode D 2 and the current limiting resistor R 1 , a parallel circuit consisting of the resistor R 9 , the polarized capacitor C 2 and the Zener diode D 3 is connected to ground. This network, which is connected in parallel, serves on the one hand to smooth pulses originating from the trigger coil L 4 and, on the other hand, to stabilize the voltage.

At the output of the trigger coil L 4 are also - connected in parallel to the input 13 of the trigger device 11 - two a gears 14 , 15 of a toggle switch 16th Its core is an integrated circuit data flip-flop 17 with a positive edge-triggered clock input C 1 , which is operated as a toggle element due to the feedback of its inverting output Q to its data input D. The voltage supply at the input U _{B of} the flip-flop 17 is derived from the first input 14 of the toggle switch 16 as follows: a polarized capacitor C 3 is charged to ground via only the positive voltage half-waves from the trigger coil L 4 through diode D 4 ; this then provides the supply voltage U _B for the flip-flop 17 . At its clock input C 1 there is the output of an inverting switching element formed from an npn transistor T 2 in an emitter circuit, the collector of which is connected to the power supply potential of the flip-flop 17 or of the power supply capacitor C 3 via the collector resistor R 5 . The control or base signal of the transistor T 2 is supplied to the trigger device 11 via a voltage divider R 3 , R 4 connected between the ground and the Zener diode D 3 .

The reset input R of the flip-flop 17 is connected to the output of a further inverting switching element from the pnp transistor T 1 in an emitter circuit with a collector resistor R 7 connected to ground. The control or Ba siseingang this pnp transistor T 1 is controlled by a voltage divider R 2 , R 6 , which at one end with the output of the trigger coil L 4 and at its end with the power supply from the power supply capacitor C 3 is connected. Whose power supply potential is supplied to the emitter of the pnp transistor T 1 .

The inverting output Q of the flip-flop 17 controls a short-circuit switch implemented by a transistor T 3 in emitter circuit via a delaying RC low-pass filter R 8 , C 4 , which then short-circuits the output or control input 10 of the switch Thy to ground.

Because of the mode of operation of this exemplary embodiment of an ignition system according to the invention, reference is made to the signal-time diagrams a) to e) in FIG. 3:

According to diagram a) of the north pole N of the permanent magnet 3 of the U-iron core induced on the first with the coil arrangement, a finally the trigger coil L4 wound legs 6 5 among other things in the trigger coil L 4 is a clamping voltage half-wave-I positive polarity on moving past. After Ver leave the first leg 6 , the north pole N moves due to the rotation 2 of the magnet wheel 1 past the second not wound leg 7 , while the south pole S is moved past the first leg 6 . This leads to a complete magnetic reversal of the iron core 5 , whereupon the second voltage half-wave II of opposite polarity and higher amplitude arises. Leaves the north pole N with further rotation 2 the area of the second leg 7 , which then magnetizes the south pole S of the permanent magnet 3 accordingly, again causes a change in the magnetic flux through the coil arrangement; a further voltage half-wave III is thus induced, the polarity of which is opposite to that of the second voltage half-wave II. Device also due to the rotation 2 of the south pole S outside the areas of the legs 6 , 7 of the U core 5 , remains in this because of the magnetization hysteresis residual magnetization positive polarity. After a complete rotation of the magnet wheel 1 , the voltage half-wave cycle I-II-III described with the period T is repeated again. As stated at the outset, the dynamic characteristic of the ignition system leads to a broadening of the second half-wave II and the third half-wave III, which manifests itself in a late passage through the trigger threshold U _Tr with the delay s due to the starting edge of the third half-wave III.

According to the present exemplary embodiment, the trigger coil L 4 delivers an ignition pulse via the diode D 2 and the output resistor R 1 to the control input 10 of the switch Thy with the rising edge of the first half-wave I when the trigger threshold U _{Tr is passed} . If it is the first rotation of the magnet wheel 1 , the ignition capacitor C 1 is not yet charged, and thus when the magnet wheel 1 passes the coil arrangement for the first time, no spark is triggered, but only the ignition capacitor C 1 and the power supply capacitor C 3 are charged (see diagram b). The subsequent second half-wave II of negative polarity from the trigger coil L 4 switches through the opposing stand R 2 of the voltage divider R 2 , R 6 through the pnp transistor T 1 , so that the flip-flop 17 is reset (see diagram c in Fig . 3). As a result, the inverting output Q of the flip-flop 17 reaches a positive potential, so that the short-circuit switch with the transistor T 3 is switched through (see diagram e) due to the second half-wave II. In this switching state, the switch Thy is activated Ignition 9 excluded, in particular the subsequent third half-wave III from the trigger coil L 4 can not trigger an ignition. However, the third half-wave III actuates the inverting switching element with the npn transistor T 2 via the pass-through diode D 2 and the input voltage divider R 3 , R 4 , the clock input C 1 of the flip having previously risen to positive potential with the second voltage half-wave II -Flops 17 is tial to ground potential. With the falling edge of the third half-wave III, the drive voltage set by the voltage divider R 3 , R 4 for the switching element T 2 is undershot, which then blocks. As a result, positive potential is applied to the clock input C 1 of the flip-flop 17 via the collector resistor R 5 of the switching element or transistor T 2 , and consequently a rising edge is generated (see diagram d) for the signal curve at the clock input C 1 ) . Due to the rising clock edge, the inverting output Q of the flip-flop 17 changes its previously positive level after a low potential. As a result, the short-circuit switch T 3 is interrupted with respect to ground, and the first half-wave I within the next revolution is not short-circuited, but reaches the control input 10 of the switch Thy. This means that the ignition 9 is triggered with the rising edge of the first half-wave I, and the ignition capacitor C 1 is discharged via the primary coil L 2 of the ignition transformer 8 . The spark that arises on the spark plug (not shown) could undesirably tip the flip-flop 17 into another state. As already described, this is countered by the reset pulse at the input R of the flip-flop 17 due to the half-wave II immediately before the ignition release (cf. in particular diagrams a and c). By coupling the voltage supply for the toggle switch 16 with the occurrence of the three voltage half-waves I, II and III, this drops during the period of the last half-wave III and the first half-wave I following within the next revolution; this deactivates the toggle switch and cannot cause ignition for times outside of voltage waves I to III.

The inventive concept goes beyond the special embodiment just described. Thus, the functions of the above trigger device 11 and / or the rocker switch 16 can be implemented with appropriate software, which runs in a microcomputer, in particular with flag registers or corresponding, reserved memory cells. The half-waves from the trigger coil could be detected by the microcomputer using an analog / digital converter. In addition, the magnet generator instead of a ro permanent magnet can be a stationary arranged vorgese hen, while a yoke wheel for magnetic inference with protruding toothed segments is used instead of the magnet wheel.

Claims (14)

1. Ignition method for internal combustion engines, especially in lawnmowers or chainsaws, in which a magnet generator for each machine revolution (T) induces a number of AC half-waves (I, II, III) by means of which an energy storage element (C 1 ) is charged and discharged from a switching element (Thy) via the primary coil (L 2 ) of an ignition transformer (L 2 , L 3 ), characterized in that the switching element (Thy) is actuated when the first half-wave (I ) a trigger threshold (U _Tr ) is reached. 2. Ignition method according to claim 1, characterized in that the rising edge of the first half-wave (I) for actuating the switching element (Thy) or for ignition ( 9 ) is used. 3. Ignition method according to claim 1 or 2, characterized records that at least one of the first half wave (I) subsequent half-waves (II, III) in relation locked on actuation of the switching element (Thy) becomes. 4. Ignition method according to one of the preceding claims, characterized by a flag which is set with the last half-wave (III) within each revolution (T) such that it signals the release of the ignition ( 9 ). 5. Ignition method according to claim 4, characterized in that the flag is reset with at least the second half-wave every revolution (T) for the purpose of locking the ignition ( 9 ). 6. capacitor ignition arrangement for internal combustion engines, with a speed-dependent alternating voltage-inducing magnet generator and the alternating voltages (I, II, III) scanning trigger device ( 11 ) for actuating one of the ignition capacitor (C 1 ) via the primary coil (L 2 ) of an ignition transformer (L 2 , L 3 ) discharging switch (Thy), in particular for carrying out the method according to one of the preceding claims, characterized by a bistable toggle switch ( 16 ) which, due to the last AC half-wave (III) within each machine revolution (T) is tilted to a state to release the operation of the switch (Thy) during the first half-wave (I) of the next revolution. 7. Ignition arrangement according to claim 6, characterized in that the toggle switch ( 16 ) with the expiry or the end flank of the last half-wave (III) is set in the release state. 8. Ignition arrangement according to claim 6 or 7, characterized in that the toggle switch ( 16 ) due to the within each revolution (T) second (II) and possibly following half-waves of the same polarity is tilted back into its original starting state and the actuation of the switch (Thy) locks. 9. Ignition arrangement according to one of claims 6 to 8, characterized in that the toggle switch ( 16 ) has a single-edge triggered toggle flip-flop ( 17 ) which within each revolution (T) due to the second (II) and possibly the following Half waves of the same polarity is reset, and on its clock input (C 1 ) the last (III) and possibly preceding half waves (i) of the same polarity act. 10. Ignition arrangement according to one of claims 6 to 9, characterized in that the power supply (U _B ) of the toggle switch ( 16 ) depends on the first and possibly following half-waves (I, II, III). 11. Ignition arrangement according to one of claims 6 to 10, characterized in that the toggle switch ( 16 ) controls a short-circuit switch (T 3 ) in the tilted-back initial state for suppressing induced trigger half-waves relative to the switch (Thy). 12. Ignition arrangement according to claim 11, characterized in that the toggle switch ( 16 ) and the short-circuit switch, a delay element (R 8 , C 4 ) is connected between. 13. Ignition arrangement according to one of claims 6 to 12, characterized in that the magnet generator has a magnet pole wheel ( 1 ) coupled to the machine revolution with tangentially offset poles (N, S) and a cooperating, stationary coil arrangement (L 1 to L 4 ) with ferromagnetic iron core ( 5 ). 14. Ignition arrangement according to claim 13, characterized in that the iron core ( 5 ) has two legs ( 6 , 7 ) directed towards the magnet wheel, one of which ( 6 ) from the coil arrangement (L 1 to L 4 ) including a charging and a trigger coil (L 1 , L 4 ) is surrounded.