Ignition device, internal combustion engine and method for its operation

Abstract

An ignition device for an internal combustion engine with a charging coil, in particular disposed on a yoke core, with a starter wheel to induce a charging voltage in the charging coil by its rotation, with a first energy store which is connected to the charging coil via a rectifier, as well as with an electrical load which for its power supply, in particular during the starting process of the internal combustion engine is connected to a second energy store, wherein the second energy store is connected to the first energy store via a voltage converter. Furthermore, the invention relates to an internal combustion engine with such an ignition device and a method for its operation.

Claims

1. An ignition device for an internal combustion engine, the ignition device comprising: a charging coil disposed on a yoke core to provide a charging voltage induced as a result of a rotational movement of a starter wheel; a first energy store connected via a rectifier to the charging coil; and an electrical load connected to a second energy store for energy supply during a starting operation of the internal combustion engine, the second energy store being connected via a voltage converter to the first energy store such that a first voltage at an input of the second energy store is greater than a second voltage output by the first energy store.

2. The ignition device according to claim 1, wherein the voltage converter is an up-converter, the first energy store being connected to the voltage converter at an input of the voltage converter, and the second energy store being connected to an output of the voltage converter.

3. The ignition device according to claim 1, further comprising a control unit that measures a voltage provided by the first energy store and/or is connected to a control input of the electrical load and measures an energy value provided by the second energy store.

4. The ignition device according to claim 1, wherein the first energy store and/or the second energy store is a capacitor.

5. The ignition device according to claim 1, wherein a voltage limiter is connected between the charging coil and the first energy store.

6. The ignition device according to claim 5, wherein the charging coil and the voltage limiter are arranged in a first module, and wherein at least the first energy store or the first and the second energy store, the rectifier, the voltage converter and/or the control unit are arranged in a second module separated from the first module.

7. A method for operating an internal combustion engine with an ignition device, the method comprising: charging a first energy store via a charging voltage induced in a charging coil via a rectifier; measuring an output voltage provided by the first energy store; and charging a second energy store, connected to the first energy store via a voltage converter, as a function of the output voltage provided by the first energy store such that a first voltage at an input of the second energy store is greater than the output voltage of the first energy store.

8. The method according to claim 7, wherein the output voltage provided by the first energy store is compared with a voltage threshold, wherein the charging of the second energy store via the voltage converter is suspended as long as the measured voltage falls below the voltage threshold.

9. The method according to claim 8, wherein the voltage threshold is set as a function of an engine speed of the internal combustion engine.

10. The method according to claim 7, further comprising: measuring an energy value provided by the second energy store, and wherein an electrical load is energized for operating or starting the internal combustion engine when the measured energy value exceeds a threshold value.

11. An internal combustion engine comprising an ignition device according to claim 1, where the starter wheel is a flywheel having at least two magnets that induce the charging voltage in the charging coil during a rotational movement.

12. The internal combustion engine according to claim 11, wherein a polarity of one of the magnets of the flywheel is oriented in a direction of rotation of the flywheel and the polarity of the other magnets of the flywheel is oriented counter to the direction of rotation.

13. The method of claim 8, wherein an impedance of a circuit formed from the charging coil and the first energy store is set in accordance with the voltage threshold.

14. The ignition device according to claim 1, wherein the second voltage output from the first energy store is compared with a voltage threshold, wherein the second energy store is charged by the first energy store via the voltage converter, the charging being suspended as long as the second voltage is below the voltage threshold.

15. The ignition device according to claim 1, wherein the second voltage of the first energy store outputs to the voltage converter, the voltage converter increasing the second voltage to an increased voltage and applying the increased voltage to the second energy store.

16. The ignition device according to claim 15, wherein an impedance of a circuit formed from the charging coil and the first energy store is set in accordance with the voltage threshold.

17. The method according to claim 7, wherein the output voltage of the first energy store outputs to the voltage converter, the voltage converter increasing the output voltage to an increased voltage and applying the increased voltage to the second energy store.

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 illustrates a block diagram of an internal combustion engine with a starter wheel and with an ignition device, which comprises a charging coil arranged on a yoke core and a first energy store and a second energy store connected thereto via a voltage converter, wherein an electrical load is connected to the second energy store,

(3) FIG. 2 illustrates the internal combustion engine, wherein the starter wheel is designed as a flywheel with magnets,

(4) FIG. 3 illustrates the internal combustion engine, wherein the starter wheel is formed as a gear,

(5) FIG. 4 is a flow diagram, a method sequence for operating the internal combustion engine having the ignition device, wherein the second energy store is charged as a function of a voltage provided by the first energy store,

(6) FIG. 5a illustrates a chronological progression of the charging voltage induced in the charging coil of the ignition device,

(7) FIG. 5b illustrates chronological progressions of the voltage provided by the first energy store when charging the second energy store, which is dependent on said voltage, or when charging the second energy store without this dependence, wherein the first energy store is charged by means of the charging voltage with a chronological progression according to FIG. 5a, and

(8) FIG. 5c illustrates chronological progressions of the capacitor voltage applied at the second energy store that is formed as a capacitor, as a function of the charging of the second energy store of the voltage provided by the first energy store or when charging the second energy store without this dependence.

DETAILED DESCRIPTION

(9) FIG. 1 shows an internal combustion engine 2 with an ignition device 4. A method B for its operation is shown as a flow chart in FIG. 4. The ignition device has a charging coil 6 which is arranged on a yoke core 8 designed as an iron core. Furthermore, the internal combustion engine 2 has a starter wheel 10 which is rotatable in a direction of rotation D, which in this case is a flywheel with four magnets 12. At a rotation of the starter wheel 10, the magnets 12 of the starter wheel 10 are moved past the charging coil 6 so that a charging voltage U.sub.L is induced in the charging coil 6, which has temporally consecutive positive and negative half waves.

(10) Further, one of the magnets 12, hereinafter referred to as a magnetic position sensor, is arranged such that upon rotation of the starter wheel in the direction of rotation D, first its north pole N is moved past the charging coil 6, and then its south pole S. The other magnets 12 are oppositely arranged, i.e., at a at rotation of the starter wheel 10 in the direction of rotation D, first its south pole S and then its north pole N are moved past the charging coil 6. In other words, the magnet position sensor 12 has a polarity that is opposite (reversed) to the other magnet 12 with respect to the direction of rotation D.

(11) Furthermore, the ignition device 4 comprises a first energy store 14, which here is a first capacitor. The latter is connected to the charging coil. In this case, a rectifier 16 formed as a diode is connected between the first energy store 14 and the charging coil, such that the capacitor is charged by means of the induced charging voltage U.sub.L, which has positive and negative half waves (method step charging LE of the first energy store, FIG. 4).

(12) The first energy store 14 is connected to a second energy store 20 via a voltage converter 18, wherein the voltage converter 18 is an up-converter and the second energy store 20 is a second capacitor. In summary, the first energy store 14 is connected to an input 22 of the voltage converter 18, i.e., to the input side, and the second energy store 20 connected to its output 24, that is, on the output side. Thus, the second energy store 20 is charged via the voltage converter 18 from the first energy store 20 (method step charging LZ of the second energy store, FIG. 4).

(13) In addition, an electrical load 26 is connected to the second energy store 20 for purposes of its power supply. The electrical load 26 has an energy requirement for its operation which in particular cannot be provided by the first energy store 14. The electrical load 26 here is a fuel-injection valve.

(14) The ignition device 4 comprises a control unit 28, which is connected to a control input 30 of the electrical load 26. The control unit 28 is further connected to a first current path 32 which extends between the second energy store 20 and the electrical load 26. Thus, the (energy, amount of energy) energy value E stored in the second energy store 20 which is designed as a capacitor can be calculated by means of the capacitor voltage U.sub.c applied thereto.

(15) In addition, the control unit 28 is connected to a second current path 34 extending between the charging coil 6 and the first energy store 14. This way, the charging voltage U.sub.L, and thus the voltage U.sub.14 provided by the first energy store 14, is measured by the control unit 28. The control unit 28 is further connected to the up-converter 18. Thus, it is possible that the second energy store 20 is charged via the voltage converter 18 as a function of the voltage U.sub.14 provided by the first energy store 14. This way, the transmission of the energy which corresponds to the induction having taken place in the charging coil 6 to the second energy store 20 is improved.

(16) The ignition device 4 comprises a voltage limiter 36 (for voltage limitation). This is connected between the charging coil 6 and the first energy store 14. By means of this, the induced charging voltage U.sub.L, which is supplied to the input side of the first energy store 14 is limited at the first energy store 14, thus preventing damage thereto. The voltage limiter 36 is connected to the control unit 28. This way, the voltage limiter 36, designed for example as a voltage actuator circuit or voltage regulator circuit, can be controlled or regulated accordingly.

(17) Furthermore, it can be seen in FIG. 1 that the ignition device 4 has a first module 38 and a second module 40, which are each shown as a dot-dashed frame. The two modules 38 and 40 are separated from each other, in other words are not formed contiguous. In the first module 38, both the charging coil 6 and the voltage limiter 36 are arranged. In the second module 40, the rectifier 16, the first energy store 14, the second energy store 20, the up-converter 18 and the control unit 28 are arranged.

(18) FIG. 2 shows a first variation of the internal combustion engine 2. This has a single module 42 which is arranged on the yoke core 8. In the module 42, the charging coil 6, the rectifier 16, the first energy store 14, the second energy store 20, the voltage converter 18, the control unit 28, the electrical load 26 and the voltage limiter 36 are arranged.

(19) The yoke core 8 is E-shaped, wherein the E-legs 44 extend out from the starter wheel 10 under formation of an air gap 46. In this case, the starter wheel 10 embodied as a flywheel has two magnets 12, of which the polarity is opposite (reversed) in the direction of rotation D. The middle E-leg is covered by the module 42.

(20) FIG. 3 shows an alternative embodiment of the internal combustion engine 2. Here, the yoke core 8 is formed substantially U-shaped, wherein the free ends of the thus formed U-legs 48 are facing a starter wheel 10, embodied here as a gear. In this case, the air gap 46 is formed between the U-legs 48 of the yoke core 8 and the gear.

(21) In this embodiment, a magnet 50 is integrated in or arranged on the yoke core 8. Upon rotation of the gear, a tooth 52 of the gear is moved past the U-legs 48 of the yoke core 8, so that when in each case one of the teeth 52 is aligned with a U-leg 48, the magnetic circuit is closed via the air gap 46 and the gear. However, if the U-legs 48 of the yoke core 8 are facing (oppose) a gap 54 formed between the teeth 52 of the gear, the magnetic circuit is interrupted due to the then comparatively large air gap 46. Upon rotation of the gear, on the basis of the above, the magnetic flux through the charging coil 6 is changed, such that the charging voltage U.sub.L is induced.

(22) FIG. 4 schematically shows in a flow chart a method for operating the internal combustion engine 2. In this case, in a first step referred to as charging LZ, the first energy store 14 is charged by means of the charging voltage U.sub.L induced in the charging coil 6. Furthermore, according to the method, the second energy store 20 is charged via the voltage converter 18 in the method step LZ.

(23) In this case, this charging step LZ is carried out as a function of the voltage U.sub.14 provided by the first energy store 14. For this purpose, the voltage U.sub.14 provided by the first energy store 14 is measured by means of the control unit 28. The measured voltage U.sub.14 is compared with a voltage threshold value SpS, and the charging of the second energy store 20 is suspended when or as long as the measured voltage (U.sub.14) falls below the voltage threshold value SpS. The control unit 28 is also used for this comparison. If the voltage U.sub.14 falls below the voltage threshold value SpS, the control unit 28 switches the voltage converter 18 to a locked state. For this purpose, a semiconductor switch 18 of the voltage converter 18 embodied as an up-converter is switched to current-blocking.

(24) The voltage threshold value is dependent on an (engine) speed R. In this case, in a table stored in the control unit 28, a value of the engine speed R is in each case assigned an amount of the voltage threshold value SpS or is determined by interpolation based on said table.

(25) The impedance of the circuit comprising the charging coil 6 and the first energy store 16 is particularly dependent on a frequency at which the first energy store 16 is charged, and thus dependent on the engine speed R. Further, due to the voltage threshold value SpS which is dependent on the speed R, the first energy store 16 is discharged during the loading of the second energy store 20 in such a way that the voltage U.sub.14 provided thereon does not fall below the voltage threshold SpS. As a result, the impedance of the circuit comprising the charging coil 6 and the first energy store 16 is changed in accordance with the voltage threshold SpS. Thus, this impedance is matched to an (input) impedance of the voltage converter 18 even with changing rotational speeds R. Consequently, power or energy transmission from the charging coil 6 to the second energy store 20 is improved.

(26) In an embodiment of the combustion engine of FIG. 1, the engine speed R is determined by means of a speed sensor designed as a Hall sensor. Alternatively, the engine speed is calculated based on a length of time t between peak values M (FIG. 5a) of the charging voltage U.sub.L induced in the charging coil 6, for example based on a length of time t between successive maximums M.

(27) In a further step EF, by means of the control unit 28, the (energy, energy amount) energy value E stored in the second energy store 20 embodied as a capacitor is determined by means of the capacitor voltage U.sub.c applied thereto. The control unit 28 switches or activates the electrical load 26 in the method step designated activation A when the capacitor voltage U.sub.c or the stored energy value E provided to the electrical load 26 exceeds a threshold value S. This is shown in FIG. 4 as the method step comparison V. The dashed arrow illustrates that the activation A takes place only when the threshold value S is exceeded by the energy value E. In this case, the threshold value S is stored or set in the control unit 28. In this way, the electrical load 26 with a comparatively high energy demand is activated only if sufficient energy is available in the second energy store 20 for the operation of said electrical load 26.

(28) FIG. 5a illustrates a chronological progression of the induced charging voltage U.sub.L. At a known rotational speed, a progression of the charging voltage U.sub.L can be determined analogously to an angular position. The charging voltage U.sub.L has a sequence of positive and negative half waves. Their maxima or minima (extreme values, peak values) M correlate with certain angular positions of the starter wheel 10 designed as a flywheel. Here, the (engine) speed R increases with time, resulting in decreasing lengths of time t between successive maxima M. The internal combustion engine 2 here is formed according to FIG. 1, wherein all the magnets 12 have the same polarity with respect to the direction of rotation D. For the sake of clarity, only two successive maxima M are provided with the reference numeral in FIG. 5a and the length of time t between these two maxima is illustrated.

(29) FIG. 5b shows two chronological progressions of the voltage U.sub.14 provided by the first energy store 16. The first energy store 16 is charged via the rectifier 16 by means of the charging voltage U.sub.L with a chronological progression as shown in FIG. 5a. The progression shown in dashed lines represents the chronological progression of the voltage U.sub.14 in which the second energy store 20 is charged as a function of this voltage U.sub.14 shown above. This is referred to below as a dependent charging process. Thus, the second energy store 20 is only charged via the voltage converter 18 if the voltage U.sub.14 is greater than the (engine) speed-dependent voltage threshold SpS.

(30) The other progression illustrated by a solid line represents the voltage U.sub.14 when charging the second energy store 20 without such a dependency (independent charging process). The voltage threshold SpS and the charging (charging behavior) of the second energy store 20 dependent thereupon, and accordingly the discharging (discharging behavior) of the first energy store 16, causes the voltage U.sub.14 provided by the first energy store 16, when the second energy store 20 has been dependently charged or the first energy store 16 has been dependently discharged, to always be higher than when the second energy store 20 is charged or the first energy store 16 is discharged without this dependency.

(31) Due to the impedance matching carried out by means of the dependence of the charging of the second energy store 20 of the voltage U.sub.14, between the circuit comprising the charging coil 6 and the first energy store 16 and the voltage converter 18, energy transmission or power transmission via the voltage converter 18 from the circuit comprising the charging coil 6 and the first energy store 16 to the second energy store 20 is improved.

(32) Thus, in the dependent charging process, the capacitor voltage U.sub.c increases faster than in independent charging. The chronological progression shown in dashed lines in FIG. 5c shows, analogously to FIG. 5b, the capacitor voltage U.sub.c with the dependency described above. The other chronological progression shown with a solid line represents the capacitor voltage U.sub.c of the second energy store 20 in the independent charging process. In this case, at any time the capacitor voltage U.sub.c is greater in the dependent charging than in the independent charging process, so that the electric load 26 is advantageously put into operation more quickly.

(33) 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