Ignition system

Abstract

An ignition system of a combustion engine has a start-up adjustment curve with a maximum rotational speed, an operating adjustment curve and a switch-over device for switching between curves. The start-up adjustment curve is selected in the case of a start-up of the combustion engine. A rotational speed curve is divided into adjacent cycles. The start of the first cycle is the point in time of the second ignition after the start-up and the start of the subsequent cycles is in each case the point in time of ignition at which the rotational speed is less than in the case of the subsequent point in time of ignition. The criterion for switching to the operating adjustment curve is whether the average of the rotational speeds of successive cycles differs by less than a first tolerance value.

Claims

1. An ignition system of a combustion engine, the ignition system comprising: a start-up adjustment curve including a maximum rotational speed, an operating adjustment curve, and a switch-over device for switching over between the start-up adjustment curve and the operating adjustment curve, and wherein: the start-up adjustment curve is selected on occasion of a start-up of the combustion engine; a rotational speed curve of the combustion engine is divided into adjacent cycles, including a first cycle and subsequent cycles; a start of the first cycle is a second point in time of ignition after the start-up of the combustion engine and a start of subsequent cycles is in each case a point in time of ignition at which the rotational speed is less than at a following point in time of ignition; and a criterion for switching over into the operating adjustment curve is whether a difference between the averages of the rotational speeds of successive cycles is less than a first tolerance value.

2. The ignition system according to claim 1, wherein the combustion engine is specifically configured for a portable working device.

3. The ignition system according to claim 1, wherein a switch-over process is blocked if the rotational speed in the case of the second point in time of ignition of the first cycle is less than at the immediately following point in time of ignition.

4. The ignition system according to claim 3, wherein, after a blocking of the switch-over process, the operating adjustment curve is selected if a difference between the rotational speeds is negative for two successive points in time of ignition.

5. The ignition system according to claim 1, wherein after a blocking of the switch-over procedure the operating adjustment curve is selected if a ratio between a number of successive points in time of ignition at which the rotational speed increases and a number of successive points in time of ignition at which the rotational speed decreases of two successive cycles is less than a limit ratio.

6. The ignition system according to claim 1, wherein a switch-over process is blocked if an average of the rotational speeds is greater than a maximum rotational speed of the start-up adjustment curve minus a first tolerance value.

7. The ignition system according to claim 1, wherein the operating adjustment curve is selected after a blocking of the switch-over process if a difference between the averages of the rotational speeds of successive cycles is less than a limit value and/or the average of the rotational speeds differs from an idling rotational speed by less than a second tolerance value.

8. A method of operating an ignition system of a combustion engine, the ignition system having a start-up adjustment curve defining a maximum rotational speed of the combustion engine and an operating adjustment curve, and the method comprises: selecting the start-up adjustment curve in case of a start-up of the combustion engine; ascertaining a rotational speed curve of the combustion engine after the start-up; as a first condition, performing a check, while the engine is operated using the start-up adjustment curve, as to whether the rotational speed continuously increases within a first number of points of time of ignition of the combustion engine; blocking a switch-over to the operating adjustment curve if the first condition is positive; only if the first condition is negative, as a second condition, performing a check as to whether the rotational speed continuously decreases within a second number of points in time of ignition of the combustion engine, and selecting the operating adjustment curve if the second condition is positive.

9. The method according to claim 8, wherein the method is configured for operating a portable working device.

10. The method according to claim 8, which comprises: dividing the rotational speed curve of the combustion engine into adjacent cycles; selecting the second point in time of ignition after the start-up as a start of the first cycle and in each case selecting a point in time of ignition as the start of subsequent cycles in which the rotational speed is less than in the case of the point in time of ignition that follows on therefrom; if the second condition is negative, establishing a third condition by performing a check as to whether a ratio between a number of successive points in time of ignition at which the rotational speed increases and a number of successive points in time of ignition at which the rotational speed decreases of two successive cycles is less than a limit ratio; blocking a switch-over to the operating adjustment curve if the third condition is negative; and selecting the operating adjustment curve if the third condition is positive, and/or cancelling the blocking of the switch-over and selecting the operating adjustment curve if the difference between the averages of the rotational speeds of successive cycles is less than a limit value.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) One embodiment of the invention is explained in detail hereinunder with reference to a drawing, in which:

(2) FIG. 1 illustrates schematically a portable working device with a combustion motor that comprises an ignition system,

(3) FIG. 2 illustrates an axial plan view of a magnetic generator of the ignition system,

(4) FIGS. 3a-3d illustrate the progressions with respect to time of the voltages prevailing in the coils of the magnetic generator and magnetic fluxes with respect to one another in respective different scalings in the respective same time section and time scale,

(5) FIG. 4 illustrates a schematic block diagram for the ignition system in accordance with the invention,

(6) FIG. 5 illustrates a start-up adjustment curve and an operating adjustment curve that are stored in the ignition system,

(7) FIG. 6 illustrates a first rotational speed progression,

(8) FIG. 7 illustrates a second rotational speed progression,

(9) FIG. 8 illustrates a first method for operating the ignition system, and

(10) FIG. 9 illustrates a further method for operating the ignition system.

(11) Parts that correspond with one another are provided with like reference numerals in all the figures.

DESCRIPTION OF THE INVENTION

(12) FIG. 1 is a schematic simplified illustration of a portable working device 2 in the form of a chain saw. The chain saw 2 comprises a tool 4 having a saw chain 6 that is coupled to a centrifugal clutch 8. The centrifugal clutch 8 has a clutch rotational speed 9 (FIG. 5) of 4,500 RPM. Consequently, the saw chain 6 is only driven if on the input side the centrifugal clutch has a rotational speed n (FIG. 6 and FIG. 7) that is greater than or equal to 4,500 U/min. The centrifugal clutch 8 is coupled on the input side to a single cylinder combustion motor 10 that operates in accordance with the two stroke method. The combustion motor 10 comprises a throttle flap having a throttle flap locking arrangement 12. In the case of the throttle flap locking arrangement 12 being activated, the throttle flap is held in a half-throttle position by means of the throttle flap locking arrangement 12 in order to feed into a combustion chamber of the combustion motor 10 a comparatively large amount of air-fuel mixture that is created by means of a carburetor 13. Moreover, the combustion motor 10 comprises a manually operated starter cable 14 by means of which a crank shaft, not illustrated in detail, of the combustion engine 10 is set in motion. Moreover, the combustion motor 10 comprises an ignition system 16 (FIG. 4).

(13) In accordance with FIG. 2, a pole wheel 18 is arranged and coupled to a crankshaft [not illustrated] of the combustion motor 10 in such a way that the pole wheel 18 rotates in a synchronous manner with the crankshaft of the combustion motor. A permanent magnet 20 is structurally integrated in the peripheral region of the pole wheel 18 in order to attach magnetically conductive pole shoes S, N around the pole regions of said pole wheel. The mentioned parts 18, 20, S, N form together a magnetic generator 22 that is rotated by the crankshaft by way of example in a direction of rotation D in an anti-clockwise manner. The magnetic poles or rather pole shoes S (south pole), N (north pole) are moved in their mentioned sequence past a soft iron magnetic yoke core 24 in each case initially past the first limb 26 of said yoke core and subsequently past the second limb 28 of said yoke core. The two limbs 26, 28 are mutually connected by way of a middle part 30 of the yoke core 24 forming a U-shape. A respective magnetic flux Ba or Bb flows periodically through an air gap 32 in the yoke core 24 or rather its limbs 26, 28 during a rotational movement in the direction D. The limb 26 through which said magnetic flux flows first in the direction of rotation D is encompassed by a charging coil U1, wherein a voltage is induced as a result of the changes in the direction of flow of the magnetic flux that occur during the rotation process.

(14) In accordance with FIG. 4, an energy storage element U4 in the form of an ignition capacitor of the ignition system 16 is charged with this charge voltage by way of a rectifier U3. An ignition switch U9 that is connected to the input of the energy storage element U4 and can be connected to ground is controlled in a specific angular position, (point in time of ignition) by a trigger switch or rather controller U8, wherein the energy storage element U4 discharges by way of the primary coil Lp of an ignition transformer U5. The latter is arranged in accordance with FIG. 2 with its primary coil Lp and its secondary coil Ls about the yoke core limb 28 that occurs in the direction of rotation D as the second limb. Likewise, a voltage supply coil U2 surrounds the second yoke core limb 28 in the end region thereof that is adjacent to the air gap 32. In accordance with FIG. 4, the output 34 of the voltage supply coil U2 is connected to a voltage supply unit U10 that generates the operating voltage VDD for the controller U8, by way of example a programmable microcontroller. Furthermore, the controller U8 of the ignition system 16 is designed so that said controller requires only a small magnitude of energy from the coil U2. For this purpose, the charging coil U2 is wound with the thin wire of the secondary winding Ls of the ignition transformer U5, and it is possible in this manner to achieve advantages with respect to the manufacturing process and storage requirements.

(15) In accordance with FIG. 4, the controller U8 is provided internally with an analogue-digital converter ADC having at least the two analogue signal sensing inputs A1, A2. A signal level attenuation circuit U7 is connected upstream of said signal sensing inputs and can be adjusted by means of said signal sensing inputs via port connections P1 . . . P4 of the controller U8 and adapted to respective signal strengths of the coils. The attenuation circuit U7 is connected at the input side to the output 36 of the charging coil U1 and parallel to the output 34 of the voltage supply coil U2 in order to feed these signals, attenuated depending upon the conditions at the port connections P1 . . . P4, to the signal sensing inputs A1, A2 of the controller U8. It is possible with the aid of a clock pulse generator U6 that is connected externally to the controller U8 to form internally in the controller U8 a clock or time counter that in combination with the analogue-digital converter ADC with reference to the alternating current half-waves, which are ascertained by way of the attenuation circuit U7, from the charging coil U1 and the voltage supply coil U2 to measure the respective duration of different angular sections. The ignition switch U9 is subsequently actuated at the determined point in time of ignition Zzp by way of the control output 36 of the controller U8 in dependence upon the evaluation of the duration of the ascertained angular sections. The discharge side 38 of the ignition capacitor U4 is connected directly to the primary coil Lp of the ignition transformer U5 that encompasses the second yoke core limb 28. The secondary coil Ls that is designed so as to transform the voltage to a higher voltage and likewise encompasses the second yoke core limb 28 is connected to said primary coil Lp, the output of said secondary coil leading to the ignition spark gap FU.

(16) Furthermore, in accordance with FIG. 4, the ignition module is provided with a reset circuit U11 and the input side 40 of said reset circuit U11 is supplied with energy from the voltage supply unit U10. The reset circuit U11 is connected on the output side to the RESET input of the controller U8.

(17) FIG. 2 illustrates the radial lines of symmetry in different rotational positions 42, 44, 46, 48, 50 for the magnetic generator 22. These correspond to the magnetic flux changes 52, 54, 56, 58 in FIG. 3d and also 60, 62, 64, 66 in FIG. 3b and to the alternating current half-waves 68, 70, 42, 74 in FIGS. 3c and 76, 78, 80, 82 in FIG. 3a, wherein the illustrated time graphs for the magnetic fluxes Ba, Bb for the individual limbs and the coil voltages U1, U2 or U5 respectively are plotted in the same time scale and same time periods with respect to one another according to their respective synchronized occurrence. The voltages on the Y-axis are illustrated with different scalings depending upon the different number of coil windings. The occurrence of the rotational positions 42-50 are likewise indicated in FIGS. 3a to 3d in order to further clarify the physical relationships. As is also evident from FIG. 3a, the voltage supply unit U10 is first supplied within one rotation or half-wave sequence with energy from the positive alternating current half-wave 78 with a peak voltage 84 so that the controller U8 can function from around 60 degrees before the top dead center TDC. The motor angular velocity is still relatively high and the angular velocity only falls drastically the closer it gets to the top dead center TDC (cf. peak voltage 86). In order for the controller U8 to function with the lowest possible energy consumption from the voltage supply unit U10, said controller is only available when a RESET signal is triggered from around the middle of the second charging voltage half-wave 70 in accordance with FIG. 3c (cf. also dotted vertical line in FIGS. 3a-3d) up to the respective calculated point in time of ignition Zzp (FIG. 6, FIG. 7), in particular in the lowest rotational speed range, in other words during the motor start-up. After the corresponding dotted vertical line 44 that in the FIGS. 3a-d passes through the respective time axes, the controller can ascertain the voltage half-waves from the charging coil U1 and the voltage supply coil U2 depending upon the signal by way of the attenuation circuit and process or rather evaluate said result in order to calculate the point in time of ignition Zzp. The currents that still flow by way of the attenuation circuit U10 can be ignored with respect to the energy consumption due to the high internal resistances.

(18) The energy storage element U4 is expediently re-charged at the end of a half-wave cycle 68-70-72-74 from the charging coil U1 with the last half-wave 74 and subsequently further charged in the next half-wave cycle with the strongest half-wave of the charging coil U1 for the next point in time of ignition Zzp.

(19) In order to capture and process the coil signals, it is also possible to use, in addition to the analogue-digital converter ADC that is integrated into the controller U8 in accordance with FIG. 4, a microcontroller having a comparator and programmable comparison voltage. The second-mentioned variant is favorable for combustion motors that have a high rotational speed because it is possible to recognize more rapidly for further processing that predetermined threshold voltages have been achieved or exceeded. Microcontrollers of this type are marketed nowadays by different semiconductor manufacturers. Together with the concept of sensing alternating current half-waves and detecting and measuring their rising or falling flanks, it is also possible in conjunction with microcontrollers of this type in the start-up rotational speed range and idling rotational speed range to recognize the direction of rotation and this is advantageous for low rotational speeds, within an angular region from the peak voltage 84 of the second positive half-wave in accordance with FIG. 3a up to the point in time of ignition.

(20) With each initialization in the region of the peak voltages 84, 86 of the voltage supply coil U2, the internal clock of the controller U8 is started and from the respective point in time of initialization 84, 86 said clock continuously counts internal pulses with constant intervals of e.g. a microsecond, said pulses being emitted by the clock pulse generator. In combination therewith, respective time stamps are stored for events that occur at the signal sensing inputs A1, A2 (said events being by way of example a coil signal below or above a threshold value that is pre-programmed for the analogue-digital ADC in accordance with FIG. 4). By way of example, the respective points in time at which the pre-programmed, negative voltage thresholds are first exceeded can be evaluated relative to one another by means of signals from the charging coil U1 on the first yoke core limb 26 and by means of the signals of the voltage supply coil U2 on the second yoke core limb 28. It is possible in a data processing facility in the controller to convert the elapsed time into a value indicating the rotational speed of the combustion motor, said elapsed time being within a half-wave sequence from the peak voltage 84 of the second half-wave up to a non-achievement of a pre-programmed, negative voltage value (corresponding by way of example to an angular position of 45 degrees before the top dead center TDC). Further time stamps can be counted and stored in further angular positions and it is possible to ascertain therefrom the change in the angular velocity whilst moving closer to the top dead center.

(21) FIG. 5 illustrates a start-up adjustment curve 88 and an operating adjustment curve 90 that are stored in the controller U8. The graph plots by how many degrees the point in time of ignition Zzp against the direction of rotation D lies before the top dead center TDC dependent upon the rotational speed n of the crankshaft of the combustion motor 10. In the case of low rotational speeds n, the angle is comparatively small and increases as the rotational speeds increase in order to achieve effective combustion within the combustion chamber of the combustion motor 10. In an idling section 92 of the start-up adjustment curve 88, the angle is constant over a rotational speed band up to a maximum rotational speed 94. In the idling section 92, the start-up adjustment curve 88 is displaced to a later point in time of ignition Zzp so that the combustion motor 10 does not accelerate too rapidly and thus has a smoother running behavior. If the rotational speed n should exceed the maximum rotational speed 94, then the air/fuel mixture that is located within the combustion chamber is not ignited and this leads to a drop in the rotational speed n. The maximum rotational speed 94 is less than the clutch rotational speed 9 of the centrifugal clutch 8. As a consequence, it is not possible to drive the tool 4 as long as the start-up adjustment curve 88 is selected.

(22) The operating adjustment curve 90 likewise comprises an idling section 96, wherein this idling section 96 is displaced with respect to the idling section 92 of the start-up adjustment curve 88 against the direction of rotation D. Alternatively, the angle of the start-up adjustment curve 88 and of the operating adjustment curve 90 is equal in the case of their respective idling section 92, 96. Furthermore, the operating adjustment curve 90 also extends in the case of rotational speeds n that is greater than the maximum rotational speed. In other words, in the case of a rotational speed n that is greater than the maximum rotational speed 94, a point in time of ignition Zzp is set and the mixture that is located within the combustion chamber of the combustion motor 10 is ignited. In so doing, the angle with respect to the top dead center TDC against the direction of rotation D is increased as the rotational speed n increases so that a comparatively effective combustion occurs and thus it is possible to accelerate the rotational movement of the crankshaft insofar as it is desired.

(23) FIG. 6 illustrates a rotational speed curve 98 of the crankshaft and thus also of the pole wheel 18 of the combustion motor 10. The combustion motor 10 operating temperature and the throttle flap locking arrangement 12 is not activated. In other words, the throttle flap is located in the idling position. In contrast thereto, FIG. 7 illustrates the rotational speed curve 98 of the combustion motor 10 with the throttle flap locking arrangement 12 activated, wherein the operating adjustment curve 90 is selected at the start-up 100 of the combustion motor 10. The combustion motor 10 is initially cold and heats up comparatively rapidly, or the combustion motor 10 is already at an operationally warm temperature at the start-up 100. As is evident in FIG. 7, the rotational speed n exceeds the clutch rotational speed 9 comparatively rapidly after the start-up 100 and the tool 4 is driven as a result. In FIG. 6 and FIG. 7, the rotational speed n of the combustion motor 10 is plotted in RPM over the angle in degrees about which the crankshaft is rotated since the start.

(24) FIG. 8 illustrates schematically a flow chart of a method 102 for operating the ignition system 16 so that the rotational speed curve 98 illustrated in FIG. 7 does not occur due to the switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 being blocked. After the start-up 100 of the combustion motor by means of the starter cable 14, the start-up adjustment curve 88 is selected in a first selection step 104 and the respective points in time of ignition Zzp are set accordingly. In a first checking step 106, the rotational speed curve 98 is divided into adjacent cycles 108. The start of the first cycle 108 is the second point in time of ignition Zzp after the start-up 100 of the combustion motor 10. Each of the cycles ends at the point in time of ignition Zzp at which the rotational speed n is less than in the case of the directly following point in time of ignition Zzp. Within each of the cycles 108, the average 110 of the rotational speed n is formed during the cycle 108. In order to simplify the calculation, only the rotational speeds n at the individual points in time of ignition Zzp of the respective cycle 108 are drawn upon. If the difference between the averages 110 of successive cycles 108 is greater than a tolerance value of 300 RPM, as is the case by way of example in FIG. 7, then the switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 is blocked in a blocking step 112. As a result, the ignition system 16 continues to be operated with the start-up adjustment curve 88 and the first checking step 106 is repeated. Insofar as the averages 110 differ by less than 300 RPM, as illustrated in FIG. 6, the switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 occurs in a second selection step 114.

(25) Furthermore, a check is performed in the first checking step 106 as to whether the rotational speed n in the case of the second point in time of ignition Zzp of the first cycle 108 is less than in the case of the directly following point in time of ignition Zzp. This is not the case both in the case of the rotational speed curve 98 illustrated in FIG. 6 and also in the case of the rotational speed curve 98 illustrated in FIG. 7. However, should this criterion be fulfilled, then the blocking step 112 is likewise performed.

(26) If the blocking step 112 has been performed, and as a result a switch-over to the operating adjustment curve 90 is blocked, this blocking is cancelled in a cancellation step 116 if a condition for cancelling the blocking has been recognized in the repeated first checking step 106. A condition of this type is by way of example whether the difference between the averages 110 of successive cycles 108 is less than a limit value, in particular 500 RPM, wherein each of the averages 110 that contributes to determining this condition is less than the respective preceding average 110. A further condition is whether the average 110 differs by less than a second tolerance value from an idling rotational speed 118, wherein the idling rotational speed 118 is essentially the rotational speed n at which the crankshaft rotates if the throttle flap locking arrangement 12 is not activated. The idling rotational speed 118 is 2,500 RPM. The second tolerance value is expediently 300 RPM. A further condition leading to the blocking being cancelled is whether the difference between the rotational speeds n is negative in the case of two successive points in time of ignition Zzp insofar as the blocking is achieved due to the increase in the rotational speed n between the second point in time of ignition Zzp of the first cycle 108 and the successive point in time of ignition Zzp.

(27) The cancellation step 116 is however not performed if the average of the rotational speeds 110 corresponds essentially to the maximum rotational speed 94 or differs from said maximum rotational speed by less than 300 RPM. As a consequence, by way of example in the case where the throttle flap locking arrangement 12 is activated, a switch-over to the operating adjustment curve 90 is not performed if it is to be assumed that the rotational speed n exceeds the maximum rotational speed 94 and the clutch rotational speed 9 essentially without delay after the switch-over has been performed.

(28) A further condition that leads to performing the cancellation step 116 is whether the ratio between the numbers of successive ignitions Zzp at which the rotational speed n increases and the number of successive ignitions Zzp at which the rotational speed n decreases is less than a limit ratio. The respective number is determined over two successive cycles 108, and the limit ratio is 1:1. In the case of the rotational speed curve 98 illustrated in FIG. 6, the ratio is 1:3, wherein the first two cycles 108 are drawn upon to form the ratio. The rotational speed n in each case increases once and decreases over the three subsequent ignitions Zzp namely in each case after the ignition Zzp that starts the respect cycle 108. In the case of the rotational speed curve 98 illustrated in FIG. 7, the ratio is 1:1, wherein in turn the first two cycles 108 are drawn upon for determining purposes. As a result, in the case of the rotational speed curve 98 illustrated in FIG. 7 the switch-over procedure continues to be blocked.

(29) FIG. 9 illustrates a further method 120 for operating the ignition system 16. The first selection step 104 is also performed in this case after the start-up 100 of the combustion motor 10 and the ignition system 16 is operated with the start-up adjustment curve 88. The resultant rotational speed curve 98 is ascertained and a check is performed in a second checking step 122 as a first condition as to whether the rotational speed n continuously increases within the first three points of time of ignition Zzp that correspond to the first three rotations of the combustion motor 10. If this is the case, then the blocking step 112 is performed and as a result a switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 is prevented.

(30) In the event that the first condition is negative, as is the case in the case of the two rotational speed curves 98 illustrated in FIG. 6 and FIG. 7, a check is performed in a third checking step 124 as to whether a second condition is fulfilled. The second condition is in this case whether the rotational speed continuously decreases over two points in time of ignition Zzp of the combustion motor 10. In other words, a check is performed as to whether three directly successive points in time of ignition Zzp exist, wherein the rotational speed n in the case of the point in time of the second ignition Zzp is less than in the case of the point in time of the first ignition Zzp and the rotational speed n in the case of the point in time of the third ignition Zzp is less than in the case of the point in time of the second ignition Zzp. This would be by way of example the case in the case of the rotational speed curve 98 illustrated in FIG. 6. In the case of the rotational speed curve 98 illustrated in FIG. 7, the second condition is however negative. In the event that the second condition is positive, the second selection step 114 is performed and the switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 is performed. There then follows normal operation 126 in which by way of example the tool 4 is operated and the working device 2 is used in a proper manner.

(31) If the second condition is negative, a check is performed in a fourth checking step 128 as to whether a third condition is fulfilled. The third condition is whether the ratio between the average number of successive points in time of ignition Zzp at which the rotational speed n increases, and the average number of successive points in time of ignition Zzp at which the rotational speed n decreases of two successive cycles 108 is less than 1:1, as already explained in connection with the method 102 illustrated in FIG. 8. In the event that the third condition is positive, the second selection step 114 is performed, otherwise the blocking step 112 is performed.

(32) In the event that the blocking step 112 is performed, a fifth checking step 130 is subsequently performed until a fourth condition is fulfilled. The fourth condition is whether the average 110 of the rotational speed n decreases within a cycle 108 over two adjacent cycles 108, in other words whether the subsequent average 110 is less than the preceding average 110. This occurs by way of example if the activation of the throttle flap locking arrangement 12 is cancelled and the throttle flap pivots as a result into the idling position. In the event that the fourth condition is fulfilled, a third selection step 132 is performed and a switch-over from the start-up adjustment curve 88 to the operating adjustment curve 90 is performed, followed by the normal operation 126.

(33) The invention is not limited to the above described exemplary embodiments. On the contrary, other variants of the invention can also be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features that are described in connection with the individual exemplary embodiments can moreover also be combined in other ways with one another without departing from the subject matter of the invention.

LIST OF REFERENCE NUMERALS

(34) 2 Portable working device 4 Tool 6 Saw chain 8 Centrifugal clutch 9 Clutch rotational speed 10 Combustion motor 12 Throttle flap locking arrangement 13 Carburetor 14 Starter cable 16 Ignition system 18 Pole wheel 20 Permanent magnet 22 Magnetic generator 24 Yoke core 26 First limb 28 Second limb 30 Middle part 32 Air gap 34 Output 36 Output 38 Control output 40 Input side 42 Rotational position 44 Rotational position 46 Rotational position 48 Rotational position 50 Rotational position 52 Magnetic flux change 54 Magnetic flux change 56 Magnetic flux change 58 Magnetic flux change 60 Magnetic flux change 62 Magnetic flux change 64 Magnetic flux change 66 Magnetic flux change 68 Alternating current half-wave 70 Alternating current half-wave 72 Alternating current half-wave 74 Alternating current half-wave 76 Alternating current half-wave 78 Alternating current half-wave 80 Alternating current half-wave 82 Alternating current half-wave 84 Peak voltage 86 Peak voltage 88 Start-up adjustment curve 90 Operating adjustment curve 92 Idling section 94 Maximum rotational speed 96 Idling section 98 Rotational speed curve 100 Start-up 102 Method 104 First selection step 106 First checking step 108 Cycle 110 Average 112 Blocking step 114 Second selection step 116 Cancellation step 118 Idling rotational speed 120 Method 122 Second checking step 124 Third checking step 126 Normal operation 128 Fourth checking step 130 Fifth checking step 132 Third selection step A1, A2 Signal sensing input ADC Analogue-digital converter Ba, Bb Magnetic flux D Direction of rotation FU Ignition spark gap Lp Primary coil Ls Secondary coil n Rotational speed TDC Top dead center P1 . . . P4 Port connection S, N Pole shoe U1 Charging coil U2 Voltage supply coil U3 Rectifier U4 Energy storage element U5 Ignition transmitter U6 Clock pulse generator U7 Attenuation circuit U8 Controller U9 Ignition switch U10 Voltage supply unit U11 Reset switch VDD Operating voltage Zzp Point in time of ignition Angle