Ignition method for an internal combustion engine and an ignition device operated accordingly

Abstract

The detection of the switching state of a stop switch at a switch terminal of an ignition device for an internal combustion engine is provided, in which an ignition pulse for controlling an electronic ignition switch is generated and a first power storage device is discharged via an ignition coil and during this discharge a voltage signal having negative and positive voltage half waves is generated, which is used for synchronizing a sampling, representing the switch state of the stop switch, particularly its closed position, of a voltage value at the switch terminal.

Claims

1. A method for detecting an opened or closed switching state of a stop switch at a switch terminal of an ignition device for an internal combustion engine, the method comprising: providing a control unit; providing an electronic ignition switch; providing the stop switch; generating an ignition pulse for controlling the electronic ignition switch, the ignition pulse being supplied from the control unit to the electronic ignition switch; discharging a first power storage device via an ignition coil and during this discharge a first voltage signal having negative and positive voltage half waves is generated and supplied to the control unit; and using the generated first voltage signal for synchronizing a sampling, representing a switch state of the stop switch, of a voltage value at the switch terminal, the voltage value being supplied to the control unit by a second voltage signal, the second voltage signal supplied from the switch terminal of the stop switch, wherein the first voltage signal is separate and independent from the second voltage signal supplied from the switch terminal of the stop switch.

2. The method according to claim 1, further comprising: precharging a second power storage device connected to the switch terminal to a first voltage value; charging the second power storage device connected to the switch terminal via at least one positive voltage half wave of the first voltage signal to another voltage value that is higher compared with the first voltage value when the stop switch is in the open position; and sampling the voltage value at the second power storage device and/or at switch terminal.

3. The method according to claim 2, wherein a temporal voltage curve of the first voltage signal is used for synchronizing the sampling at the second power storage device or at the switch terminal.

4. The method according to claim 1, wherein a first positive voltage half wave of the first voltage signal is used for synchronizing the sampling of the voltage value at a sampling time during the first positive voltage half wave of the first voltage signal.

5. The method according to claim 1, wherein the switching state of the stop switch is inferred from a deviation of the current voltage value from a threshold value, wherein a closed position of the switching state is detected when the voltage value is smaller than the threshold value, and wherein an open position of the switching state is detected when the voltage value is greater than or equal to the threshold value.

6. The method according to claim 1, wherein a closed state of the stop switch is inferred, when the voltage value at the switch terminal during a first positive half wave of the first voltage signal and after the expiration of a timing member falls below a threshold value, and wherein the timing member is started at time of the generation of the ignition pulse or at the ignition time or at a time between the time of the generation of the ignition pulse and a temporal occurrence of a characteristic voltage value of the first voltage signal.

7. The method according to claim 1, wherein at least positive voltage half waves of the first voltage signal, arising during the discharge of the power storage device, are supplied to the switch terminal.

8. The method according to claim 1, wherein, depending on a rotary position of a magnetic generator coupled to the internal combustion engine, a charging coil signal with alternating negative and positive voltage half waves is generated, and wherein the charging coil signal is used for charging the first power storage device.

9. The method according to claim 8, wherein, during a positive voltage half wave or during a first positive voltage half wave of the charging coil signal and before the generation of the ignition pulse the voltage value is sampled at the switch terminal of the ignition device to detect the switching state of the stop switch, and wherein the closed or open position of the stop switch is inferred from a deviation of the sampled voltage value from a first voltage value and/or a threshold value.

10. The method according to claim 1, wherein the switch state is a closed position.

11. The method according to claim 1, wherein the stop switch is a separate switch from the electronic ignition switch.

12. An ignition device for an internal combustion engine, comprising: a magnetic generator coupled to the internal combustion engine; a charging coil, which, depending on a rotary position of the magnetic generator, generates a charging coil signal with alternating negative and positive voltage half waves; a stop switch; a switch terminal for the stop switch; an electronic ignition switch; and a control unit, wherein the control unit generates an ignition pulse for switching through the electronic ignition switch to discharge a power storage device via a primary winding of an ignition transformer, wherein the control unit has a synchronization input, to which a first voltage signal, arising during the discharge of the power storage device, is supplied, wherein the control unit has a comparator input, to which a second voltage signal and a voltage value, arising during an actuation of the stop switch at the switch terminal, is supplied from the switch terminal of the stop switch, wherein the control unit has a comparator function, which compares a voltage value at the switch terminal and/or at a second power storage device with a threshold value, a comparison result providing an opened or closed switch state of the stop switch, and wherein the first voltage signal is separate and independent from the second voltage signal supplied from the switch terminal of the stop switch.

13. The ignition device according to claim 12, wherein the control unit with or after the generation of the ignition pulse, depending on a course of the primary side of the ignition transformer or a voltage signal tapped at a trigger coil, starts a timing member, and wherein after expiration of the timing member, a sampling of the current voltage value occurs at the switch terminal or at the second power storage device.

14. The ignition device according to claim 12, wherein the control unit with the occurrence or at a specific time of a first positive voltage half wave of the charging coil signal starts a timing member, during which a sampling or a sampling sequence with a number of scans, of the current voltage value occurs at the switch terminal or at the second power storage device.

15. The ignition device according to claim 12, wherein the stop switch is a separate switch from the electronic ignition switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows schematically a magnetic ignition device for an internal combustion engine, for example, of a hand-held device or tool powered by a combustion engine;

(3) FIG. 2 shows schematically as a detail the circuitry structure of the ignition device with a control unit with a switch terminal and signal terminal connected thereto;

(4) FIG. 3 shows in a voltage-time diagram the curve of a voltage or synchronization signal after triggering of an electronic ignition switch;

(5) FIG. 4 shows the voltage level at the switch terminal of the ignition device or its control unit for a stop switch;

(6) FIG. 5 shows schematically the magnetic generator of the ignition device including a magnet wheel with magnets and an iron core and coils arranged thereon;

(7) FIG. 6 shows time-dependent curves of the charge voltage of the charging coil (FIG. 6c) and other coils or windings (FIG. 6a) and of magnetic fluxes (FIGS. 6b and 6d) in the legs of the iron core according to FIG. 2; and

(8) FIG. 7 shows the time curve of the charging voltage and a primary coil voltage, as well as a voltage at a signal terminal (stop port) of the control unit in the form of preferably a microcontroller (C).

DETAILED DESCRIPTION

(9) FIG. 1 shows in a block diagram an ignition device (magnetic or capacitor ignition device) 1 with a magnetic generator 2 in the form of a magnet wheel which has a magnet with a north and south pole N, S and which rotates synchronously with a combustion engine not shown in greater detail. In this case, the magnetic field, generated by magnetic generator 2, amplified by an iron core 3, induces a voltage or a current in a charging coil 4 and optionally in another coil winding or trigger coil 5 and in an ignition transformer 6, often also called an ignition generator or ignition coil, with a primary winding 7 and a secondary winding 8. The positive half waves of a charging voltage (charging current) of charging coil 4 are fed via a rectifier (diode) 9 to a first power storage device 10, called an ignition capacitor hereinafter. The positive half waves of the charging voltage charge ignition capacitor 10 via primary winding (primary coil) 7 of ignition transformer 6, said winding connected in series with the capacitor, for example, to ground.

(10) A voltage supply (power supply) 11 for a control unit and/or regulating unit 12 preferably in the form of a microprocessor or microcontroller is supplied with power via charging coil 4, according to the signal line shown as a dashed line in FIG. 1, or optionally via trigger coil 5. Voltage source 11 provides the supply voltage V.sub.DD for control unit and/or regulating unit 12, called a control unit hereinafter.

(11) Unit 12 has a control output 13, which feeds an ignition pulse S.sub.Z to a control terminal (base, gate) of an electronic semiconductor switch (ignition switch) 14, for example, a thyristor, in order to control it and to discharge ignition capacitor 10 via primary winding 7 of ignition transformer 6 and to generate a high voltage pulse in secondary coil 8 of ignition transformer 6. This causes a sparkover for its part at a spark plug 15 of the combustion engine.

(12) Ignition device 1 is moreover provided with a stop switch terminal (stop terminal) 16 or has such a terminal. A stop switch 17 is or can be connected to stop terminal 16. Stop terminal 16 is assigned a terminal (input/output) 18 of control unit 12. In particular, control unit 12 is connected via said terminal (terminal pin) 18 to stop terminal 16 in terms of circuitry and/or signals.

(13) Control unit 12 moreover has a terminal (signal or synchronization input) 19. A voltage signal or synchronization signal S.sub.1 is fed to this terminal; the signal is tapped between ignition capacitor 10 and primary winding 7 of ignition transformer 6 or at the optionally present trigger coil 5.

(14) A voltage signal S.sub.2 present at switch terminal 16 in the form of appropriate voltage values or voltage levels is supplied to terminal 18, also called a comparator input or comparator terminal pin hereinafter. A second power storage device 21, particularly in the form of a capacitor, connected to switch terminal 16 and preferably to ground, is also charged via said terminal 18 and particularly via a serial resistor 20 (FIG. 2).

(15) FIG. 2 shows a circuit component of ignition device 1 with control unit 12 which is configured as a microprocessor and has ignition switch 14, ignition transformer 6, and ignition capacitor 10. Said component is run via rectifier (diode) 9 to a terminal 22, which for its part is run to charging coil 4. On the secondary side, ignition transformer 6 is run to a terminal 23 of ignition device 1, to which, for example, spark plug 15 is or can be connected. The second power storage device in the form of capacitor 21, which is connected to ground, is assigned to switch terminal 16.

(16) On the primary side, ignition transformer 6, i.e., its primary winding 7, is run via a series connection with a serial diode (rectifier) 24 and an ohmic resistor 25, downstream from it, to switch terminal 16 or to its connection to terminal pin 18 of control unit 12. The positive voltage half waves S.sub.(+) of voltage signal S.sub.1 are fed via diode or rectifier 24 to switch terminal 16 and therefore also to capacitor 21. The charging of capacitor 21 occurs via terminal 18 and the downstream resistor 20 and/or via a charging resistor 26, which is connected to a terminal (charging terminal) 27 of control unit 12.

(17) Voltage signal S.sub.1 is supplied to unit 12 as a synchronization signal via synchronization terminal 19. Unit 12 has a comparator function 28 which is indicated by the dashed lines and can be configured in terms of programs, circuitry, and/or components. Said function 28, also designated as a comparator hereinafter, monitors signal S.sub.2 and at specific times samples the state of charge of capacitor 21 or the voltage value or level U.sub.21 thereof and compares this current voltage value U.sub.21, also present at switch terminal 16, with a threshold value U.sub.SW.

(18) Comparator function 28 is activated only during a specific time interval. In other words, a sampling of voltage value U.sub.21 of signal S.sub.2 or a sampling of its level occurs only synchronously with a specific timeframe or at a specific time of voltage signal S.sub.1. Said timeframe or said time interval or said time is suitably the first positive half wave S.sub.(+) or lies within said half wave S.sub.(+) of signal S.sub.1 shown in FIG. 3.

(19) FIG. 3 shows this voltage signal S.sub.1, which arises during ignition pulse S.sub.Z or when the ignition spark is turned on and is used for synchronizing the sampling of voltage value U.sub.21 at switch terminal 16 and is accordingly sampled and evaluated in control unit 12.

(20) FIG. 4 shows the voltage level U.sub.21, changing with time t, of signal S.sub.2 at switch terminal 16. During the sampling of this voltage level U.sub.21 at switch terminal 16, the second power storage device (capacitor) 21, connected to switch terminal 16, is already charged with, e.g., V.sub.DD=5V, to a voltage value U.sub.21=V.sub.DD. In this regard, the charging voltage and thereby voltage level U.sub.21 at switch terminal 16 is set to a specific voltage value, which preferably corresponds to the supply voltage V.sub.DD. Capacitor 21 is precharged to this value V.sub.DD.

(21) It is assumed that at time t.sub.0 of ignition pulse S.sub.Z for controlling ignition switch 14 is or has been generated by control unit 12. The discharge of ignition capacitor 10 via primary winding 7 of ignition transformer 6 begins at time t.sub.1. As a result, ignition capacitor 10 is periodically charged and discharged, so that between ignition capacitor 10 and primary winding 7 of ignition transformer 6 the voltage signal S.sub.1 appears with respect to the amplitude of negative voltage half waves S.sub.() and positive voltage half waves S.sub.(+) fading over time t.

(22) Whereas the pulse inherent in voltage signal S.sub.1, specifically the first negative half wave S.sub.(), following the time t.sub.1, with the largest amplitude is used as the primary pulse for generating the high-voltage on the secondary side of ignition transformer 6 and therefore again for generating the ignition spark, the first positive half wave S.sub.(+) with a relatively highest positive voltage amplitude over time starting at time t.sub.2 and ending at time t.sub.3 and within time interval t.sub.3t.sub.2=t at switch terminal 16 and with a connected stop switch 17 is connected via the stop switch to ground.

(23) If stop switch 17 is in closed position, then a high current flow, generated following the first positive half wave S.sub.(+) of voltage signal S.sub.1, is used to clean the possibly oxidized or contaminated contacts of stop switch 17. Because capacitor 21 is precharged to the voltage value V.sub.DD particularly already before this time interval t=t.sub.3t.sub.2 of the positive half wave S.sub.(+), an additional charging voltage U.sub.21>V.sub.DD is present at time t.sub.a within this time interval t=t.sub.3t.sub.2 and therefore additional power is available at switch terminal 16. In other words, during the generation of the ignition spark and particularly during the time interval t=t.sub.3t.sub.2 a higher current flow is available than only with the positive half wave S.sub.(+) of voltage signal S.sub.1 and than only with voltage value U.sub.21=V.sub.DD, in order to clean reliably the contacts of stop switch 17 in its closed position and to achieve a reliable contacting in the closed position of stop switch 17.

(24) As is illustrated in FIG. 4, the positive half wave S.sub.(+) of voltage signal S.sub.1 at switch terminal 16 can produce a level or voltage value U.sub.21 increased up to 6-fold compared with the voltage value (level) U.sub.21=V.sub.DD, when stop switch 17 is opened. The voltage value U.sub.21 also increased beyond time t.sub.3 can be attributed to the presence of second capacitor 21. Without this capacitor 21, the signal S.sub.2 within the time interval t=t.sub.3t.sub.2 would follow the curve indicated by dashed lines.

(25) If stop switch 17 is in the closed position, then following the current flow across stop switch 17 during the time interval t=t.sub.3t.sub.2, a shunt with a correspondingly low voltage level or value U.sub.21 is to be expected, as long as the switch contacts of stop switch 17 are beset with contaminations. This is illustrated in the bottom diagram in FIG. 4. Whereas before t.sub.2 capacitor 21 is already charged or precharged by means of control unit 12, control unit 12 turns off preferably after t.sub.3, therefore after the spark generation, the function of the additional charging of capacitor 21 by means of signal S.sub.1 beyond the value U.sub.21=V.sub.DD for reasons of energy efficiency or power saving.

(26) Moreover, with use of the voltage value U.sub.21 a closed position of stop switch 17 can be reliably inferred, i.e., that its contacts are in fact contacted and cleaned, when the voltage level or value U.sub.21 at switch terminal 16 is below the threshold value U.sub.SW. This is smaller than the voltage value U.sub.21=V.sub.DD and is suitably between 2V and 4V, for example, U.sub.21=3.5V. In other words, it can be assumed from this that in the closed state of stop switch 17 with cleaned and contacted switch contacts, a shunt is negligible and the voltage level U.sub.21 is smaller than this threshold value U.sub.SW and thereby is zero or close to zero. If the voltage level or value U.sub.21 at switch terminal 16 is greater than or the same as threshold value U.sub.SW, therefore it can be assumed that stop switch 17 is opened.

(27) The sampling of the voltage level U.sub.21 at switch terminal 16 by means of comparator function 28 of control unit 12 proceeds synchronously with that of voltage signal S.sub.1 and thereby during the first positive half wave S.sub.(+). An especially suitable sampling time t.sub.a (FIG. 4) is in terms of time within the time interval t between the times t.sub.2 and t.sub.3 of the first positive half wave S.sub.(+) after a voltage drop or voltage breakdown has occurred, whereas a corresponding current is provided via charging coil 4 in addition across closed stop switch 17.

(28) In an advantageous refinement of the invention, therefore a timing element t.sub.n is started for or during the synchronization. The starting time of said timing element t.sub.n can be the time t.sub.0 for generating ignition pulse S.sub.Z or the ignition time. The corresponding timing element t.sub.2 then runs down to time t.sub.a, at which time t.sub.a the sampling of the current voltage level U.sub.21 at switch terminal 16, therefore the stop sampling occurs. An open or closed stop switch 17 can be inferred from the voltage value U.sub.21 or U.sub.21 at switch terminal 16.

(29) An alternative timing member t.sub.3 is started at time t.sub.1, at which the first negative half wave S.sub.() of voltage signal S.sub.1 and therefore the generation of the ignition pulse S.sub.Z or of the ignition spark begin. This time interval t.sub.a again ends between the times t.sub.2 and t.sub.3 of the first positive half wave S.sub.(+) of voltage signal S.sub.1, preferably at time t.sub.a. A further suitable timing member is the time interval t.sub.4 which begins at time t.sub.2 and again ends at time t.sub.a.

(30) The synchronization of the comparator or the comparator function 28 with the voltage signal S.sub.1 therefore occurs preferably during the first positive half wave S.sub.(+)and/or by means of a timer with use of one of the time intervals t.sub.n. The sampling time t.sub.a is thereby in terms of time preferably sufficiently distant from time t.sub.2. The sampling time t.sub.at.sub.2+t/2 is especially preferred.

(31) FIG. 5 shows the functionality of magnetic generator 2 of ignition device 1 according to the generator or dynamo principle. A permanent magnet M with a north pole N and a south pole S is arranged on the magnet wheel P in an exposed circular segment. The preferably U-shaped iron core 3 with two iron core legs Ka and Kb and with a connecting or middle leg Km is arranged opposite to magnet wheel P. Iron core 3 supports charging coil 4 or ignition transformer 6 and optionally trigger coil 5 on its legs Ka and Kb.

(32) Magnet wheel P rotates synchronously with a crankshaft of the combustion engine or internal combustion engine. Magnet wheel P rotates, for example, in a counterclockwise rotation direction D. The particular magnetic flux Ba or Bb periodically flows via an air gap L through iron core 3 or its legs Ka, Kb with each rotation of the magnet wheel P. As a result, a charging coil signal U.sub.LS, also called a charging voltage hereinafter, whose time curve is shown in FIG. 6c, is induced in charging coil 4. FIG. 6a shows the temporal voltage curve in ignition transformer 6 and in trigger coil 5. The field profiles in legs Ka and Kb are shown in FIG. 6d or 6b.

(33) FIG. 7 shows the time course of the charging voltage U.sub.LS with inverted negative half waves U.sub.LS(). Moreover, FIG. 7 shows voltage signal S.sub.2 at switch terminal 16, which is supplied via terminal pin 18 to control unit 12.

(34) As is evident in FIG. 7, a sampling or scanning of signal S.sub.2 at switch terminal 16 begins at time t.sub.x1 and ends, for example, at time t.sub.x2. This so-called low-voltage sampling occurs before the ignition time t.sub.z, but during the same rotation of magnet wheel P and therefore during the same rotation of magnetic generator 2. The signal S.sub.2 represents the time curve of the charging voltage or of the voltage value U.sub.21 at capacitor (parallel capacitor) 21 (FIG. 2). This signal S.sub.2 at stop terminal or switch terminal 16 is sampled repeatedly. If a voltage value U.sub.21 (low level) is detected repeatedly that is smaller than U.sub.21=V.sub.DD, thus this is an indication for actuating stop switch 17 in its closed position.

(35) Moreover, the sampling or scanning of the signal level or value U.sub.21 at switch terminal 16 within or during the first positive half wave of the charging voltage U.sub.LS occurs in accordance with the voltage half wave 4 in FIG. 6c. If a low level at switch terminal 16 is detected less often, thus no closing of stop switch 17, and accordingly no stop command, is detected. This low-voltage sampling occurs suitably in addition to and thereby before the sampling of the actuation state of stop switch 17 at ignition time t.sub.z, but during the same rotation of magnetic generator 2.

(36) The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived herefrom by the person skilled in the art, without going beyond the subject matter of the invention. Particularly, further all individual features described in relation to the exemplary embodiments can also be combined with one another in a different manner, without going beyond the subject matter of the invention.

(37) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.