Ignition device for an internal combustion engine and method for its operation

Abstract

Ignition device for an engine unit (19) with a two-stroke engine (1) in a portable, hand-held work device, [01] wherein the two-stroke engine (1) comprises a piston (6), a combustion chamber (5) with a spark plug (15) and a crankshaft (4) driven by the piston (6) to rotate, [02] with an inlet window (8) for supplying combustion air into the combustion chamber (5) and an outlet (9) for removing combustion gases from the combustion chamber (5) [03] and with an alternating current generator (16) driven by the crankshaft (4) which is attached to the engine unit (19) and which outputs successive alternating voltage signals (S) within one crankshaft revolution, [04] and with an ignition unit (18) which triggers an ignition spark at the spark plug (15) at a preselectable time, characterized in that [05] that the ignition unit (18) is designed as a separate assembly from the motor unit (19), [06] that the electrical alternating voltage signal (S) of the alternating current generator (16) is supplied to the ignition unit (18) as an information signal sufficient for the operation of the two-stroke engine (1), [07] that the alternating voltage signal (S) is supplied to a unit (30) for energy conditioning and to a unit (33) for conditioning information for controlling the two-stroke engine (1), [08] and that the information signal sufficient for the operation of the two-stroke engine (1) is an angle information signal (W) processed from the alternating voltage signal (W) for the rotationally correct assignment of the mechanical crankshaft angle position to the alternating voltage signal (S).

Description

[0001] The invention relates to an ignition device for a motor unit with a two-stroke engine in a portable, hand-held power tool, wherein the two-stroke engine comprises a piston, a combustion chamber with a spark plug, and a crankshaft driven by the piston. The engine includes an intake port for supplying combustion air to the combustion chamber and an exhaust port for removing combustion gases from the combustion chamber. An alternating current generator, which is attached to the motor unit and outputs successive alternating voltage signals within one crankshaft revolution, is driven by the crankshaft. The ignition unit triggers a spark at the spark plug at a preselectable time.

[0002] Modern internal combustion engines, such as those used in handheld portable power tools like chainsaws, brush cutters, angle grinders, blowers, and the like, are controlled by ignition systems. These systems require an AC signal to supply high voltage to a spark plug and an ignition trigger, which is positioned approximately 40° before top dead center (TDC) and initiates the ignition. The ignition trigger must be mounted in the correct rotational position on the circumference of a rotating flywheel on the crankcase. However, variations in the mechanical arrangement of the ignition trigger occur in production models, which can affect the ignition timing. Furthermore, the fixed arrangement of the ignition generator, ignition module, and speed sensor is often problematic, as these components are frequently located within the cooling air duct on the fan wheel, thus occupying valuable space.This can lead to cooling problems, which puts more thermal stress on the cylinder.

[0003] From EP 1 321 651 A2, a generic ignition device is known which shows an alternating current generator but requires a sensor to control the ignition. Two electrical signals are supplied to the ignition unit: on the one hand, the signal from the sensor coil, and on the other hand, the energy signal from the primary winding.

[0004] EP 1 795 745 A2 specifies a sensor coil whose output signal controls the ignition unit, and further shows an ignition coil with a primary winding and a secondary winding that ensures the energy supply to the spark plug. Two electrical signals are supplied to the ignition unit: the signal from the sensor coil and the energy signal from the primary winding.

[0005] Publications DE 103 23 558 A1, DE 196 54 290 A1 and DE 196 14 462 A1 show further ignition units of similar construction.

[0006] The invention is based on the objective of simplifying an ignition device in such a way that precise ignition is possible regardless of its design arrangement, and of providing a method for operating such an ignition device.

[0007] The problem is solved according to the invention by the characterizing features of claim 1. A method for operating the ignition device is described in claim 24.

[0008] The ignition unit is designed separately from the engine unit, with the signal generator, which is advantageously designed as an AC generator, being connected to the ignition unit via only one electrical line. The AC voltage signal from the signal generator is the only information signal sufficient for operating the internal combustion engine and is fed to the ignition unit. This signal is then processed in an energy conditioning unit and in a separate unit for generating angular information.

[0009] The information signal sufficient for operating the internal combustion engine is preferably a processed angle information signal, which serves to assign the mechanical crankshaft angle position to the alternating voltage signal in the correct rotational position.

[0010] This design allows the ignition unit to be positioned anywhere on the internal combustion engine or engine unit; only the AC voltage signal needs to be supplied to the ignition unit. The ignition unit is then connected to the spark plug of the internal combustion engine via a suitable high-voltage cable. This eliminates the need for rotary encoders or similar devices to detect the crankshaft's angular position. The actual mechanical crankshaft position is determined electronically based on the generator's AC voltage signal and—once the actual mechanical crankshaft position is detected—permanently assigned to the crankshaft rotation signal.This "locking" of the AC voltage signal to the actual mechanical angular position of the crankshaft can occur as early as the first crankshaft revolution, because the angle information signal derived from the AC voltage signal exhibits characteristic features that correspond to the design-defined crankshaft angle positions. For example, the opening of the exhaust port or the transfer port is clearly defined in the angle information signal, allowing the ignition unit to establish a fixed correlation between the AC voltage signal and the actual mechanical crankshaft angle position even during the first crankshaft revolution. Once the AC voltage signal is locked to the crankshaft angle position, it is only necessary to count the successive zero crossings, which, due to the design of the AC generator, follow one another at known crankshaft angle intervals.

[0011] The extensive decoupling of the signal generator and ignition unit opens up new possibilities for the ignition unit's arrangement. It can now be positioned in locations that were not possible with previous designs. Furthermore, if the ignition unit is split into modules, the high-voltage unit, for example, can be positioned near the spark plug or integrated into the spark plug, while the processor unit can be located in a thermally advantageous position, such as on the side of the crankcase facing away from the cylinder (crankcase pan).

[0012] Eliminating the need for rotary encoders to detect the actual mechanical crankshaft angle simplifies the mechanical design of the ignition system itself and also leads to more precise ignitions, as mechanical tolerance errors associated with mounting a rotary encoder are eliminated. Each system in a series calibrates itself during operation, meaning that, for example, in the mass production of handheld power tools, every single manufactured device operates optimally due to this self-calibration.

[0013] The angle information signal itself consists of the successive zero crossings of the preferably continuous alternating voltage signal, wherein these zero crossings are preferably evenly distributed over one crankshaft revolution.

[0014] The distance between two zero crossings forms a zero interval, and in a particular embodiment of the invention, the interval speed is determined for each zero interval. The interval speeds calculated in this way form a speed profile that constitutes the angle information signal, based on which the AC voltage signal can be locked onto the actual mechanical crankshaft angle position.

[0015] The locking of the AC voltage signal to the mechanical crankshaft angle position can always occur if the processed angle information signal has a significant feature that is firmly assigned to a specific known mechanical rotational angle position of the crankshaft.

[0016] In a suitable embodiment, a zero interval corresponds to the nth part of a crankshaft revolution, where n is an integer greater than 6.

[0017] Preferably, the number n is between 6 and 24, particularly 12. Twelve zero crossings correspond to six periods T of an alternating voltage signal, where one period T corresponds to 60°KW.

[0018] To simplify the alignment of the AC voltage signal with the mechanical crankshaft angle, the rotational position of the AC generator on the engine unit and the piston's top dead center are advantageously coordinated such that a zero interval is symmetrical to the piston's top dead center. The coordination is expediently such that a zero point of the induced AC voltage signal is preferably located approximately 15° crank angle before the piston's top dead center. This also ensures that, during engine start-up, a partial load of the half-wave can be used to supply power to the electronics, meaning the system is operational early in the starting process even without a battery. This results in favorable starting conditions. The coordination can also be configured so that the signal curve is at its average value at minimum engine speed.This allows for the simple determination of a minimum interval speed, which, as a significant characteristic, indicates the piston's top dead center position. It can be useful to differentiate the speed profile of the interval speeds, i.e., the angle information signal; the difference curve then shows significant spikes that can be assigned to a characteristic mechanical crankshaft angle position, e.g., the piston's top dead center position.

[0019] In this embodiment, a claw-pole generator or a star generator is used as the signal generator, which is simple in design and requires little space. The stator of the generator is conveniently fixed to the crankcase, while the rotating magnet ring is non-rotatably connected to a fan wheel of the internal combustion engine.

[0020] The energy generated by the generator not only powers the ignition unit itself and its high-voltage unit, but can also operate a heating device such as a carburetor heater, grip heater, or similar. External connections can also be used to power light sources, target lasers for angle grinders, or similar devices. In a further development of the invention, energy from the AC signal can also be used to power energy storage devices such as capacitors, accumulators, or similar. The total energy of the AC signal can be distributed as needed between individual devices and the ignition system, with supply priorities also being defined. For example, the ignition system receives energy with priority 1; only when the ignition system has received sufficient energy for the reliable operation of the internal combustion engine are other devices with priorities 2, 3, etc., powered.It is also advantageous to design the generator with at least two windings, whereby one of the windings supplies a first consumer such as the high-voltage supply and the other winding supplies a second, different consumer such as the ignition or a heater.

[0021] When electrical loads are operated from the generator, it is advantageous for accurately determining the position of the zero crossing of the voltage signal to interrupt the current flow through a connected electrical load in the vicinity of the zero crossing. This reliably prevents potential signal shifts caused by inductances or capacitances. It has proven advantageous to interrupt the current flow, for example, by switching off the load in the region from approximately 5°KW before the zero crossing to approximately 1°KW after the zero crossing.

[0022] The ignition unit advantageously consists of a control unit, such as a microprocessor or the like, and a separate high-voltage unit. This allows the control unit to be located separately from the high-voltage unit in a thermally favorable area of ​​the machine. It is advantageous to arrange it on or near a component of the engine unit. For example, the control unit can be located on the mixture preparation device, such as a carburetor. The engine unit is advantageously suspended together with the carburetor in the housing of the machine via anti-vibration elements, with the carburetor being advantageously connected elastically to the internal combustion engine, for example, via an elastic channel. Arranging the control unit on the carburetor housing has the advantage of vibration decoupling, since the carburetor is decoupled from the housing via the anti-vibration elements and, due to the elastic connection to the internal combustion engine, is vibrationally isolated from it.This achieves a vibration-isolated arrangement of the electronic control unit without requiring the electrical connecting lines to the high-voltage unit or generator to be routed across the AV gap. A thermally efficient arrangement has been found that is low in vibration and also low in dirt.

[0023] Alternatively, the control unit can also be located on or near the crankcase, for example, near the generator below the cylinder. Another advantageous location is on the part of the crankcase furthest from the cylinder, i.e., at the bottom of the crankcase.

[0024] Claim 24 describes a method for processing the preferably continuous AC voltage signal of a signal generator driven by a shaft of an internal combustion engine in order to assign an angle information signal to the rotating shaft in accordance with its angular position. For this purpose, the generator is constructed such that the predetermined interval between the zero crossings of the AC voltage signal corresponds to an nth part of a complete shaft revolution, where n is an integer. The time interval between successive zero crossings is recorded, and an interval speed is determined for each zero crossing interval. The speed values ​​of the interval speeds are plotted against the shaft angle and represent a speed profile that forms an angular information signal for the mechanical angular position of the shaft.

[0025] This speed profile is scanned for a minimum speed, and this minimum speed is then assigned to the crankshaft's angular position at the piston's top dead center. Under certain operating conditions, such as the occurrence of torsional vibrations or a "blub-blub" start (starting at very low speed), it is advisable to verify this assignment.

[0026] Further features of the invention will become apparent from the further claims, the description, and the drawing, in which an embodiment of the invention described in detail below is illustrated. The drawing shows: Fig. 1 In schematic representation, a motor unit with an associated ignition unit, Fig. 2 a schematic representation of an alternating current generator driven by the crankshaft of the internal combustion engine of the engine unit in a design as a claw pole generator, Fig. 3 an idealized voltage curve of a multi-pole AC generator, plotted against the crankshaft angle, Fig. 4 a schematic representation of a crankshaft revolution with assignment of the zero crossings of the voltage signal according to Fig. 3, Fig. 5 a real AC voltage signal from an AC generator according to Fig. 2, Fig. 6 a speed profile formed from interval speeds of an alternating current generator driven by an internal combustion engine, Fig. 7 a schematic representation of the rotational position of the AC generator with respect to a minimum speed, Fig. 8 a reference curve to a typical engine speed profile during the starting process, Fig. 9. A speed profile of an internal combustion engine during the starting process with the inclusion of a cumulative error relative to the reference curve. Fig. 8, Fig. 10 a speed profile of an internal combustion engine during the starting process with a superimposed differentiated speed profile curve D, Fig. 11 the course of the angular error of the crankshaft position when extrapolating the rotational angular position of the crankshaft from one zero point to the next zero point. Fig. 12 a schematic representation of an alternating current generator designed as a star generator.

[0027] In the schematic representation in Fig. The engine unit 19 comprises an internal combustion engine 1, which is in particular designed as a two-stroke engine. The ignition device according to the invention is not limited to use in single- or multi-cylinder two-stroke engines; it can also be used in single- or multi-cylinder four-stroke engines or similar engines, in particular reciprocating piston engines.

[0028] The internal combustion engine 1 of the engine unit 19 comprises a cylinder 2 with a crankcase 3 in which a crankshaft 4 is rotatably mounted. A combustion chamber 5 is formed in the cylinder 2, which is bounded by a reciprocating piston 6. The piston 6 is connected to the crankshaft 4 in the crankcase 3 via a connecting rod 7 and drives the crankshaft by rotating it. In the illustrated embodiment, an intake port 8 for combustion air and / or mixture opens into the combustion chamber 5. The intake port 8 is provided at the end of a transfer port 14 in the wall of the cylinder 2, the other end of which is open towards the crankcase 3. Furthermore, an exhaust port 9 is provided through which combustion gases are discharged from the combustion chamber 5.

[0029] A fuel / air mixture is supplied to the internal combustion engine 1 via a carburetor 10, with the mixture inlet 11 opening into the crankcase 3. Combustion air is drawn in through an air filter 12 and supplied to the mixture inlet 11 via the intake manifold 13 and the carburetor 10. As the piston 6 moves upwards, the mixture is drawn into the crankcase 3 through the mixture inlet 11 due to the vacuum created in the crankcase 3. As the piston 6 moves downwards, the mixture drawn into the crankcase 3 is guided through the transfer port 14 to the intake port 8 and flows into the combustion chamber 5. As the piston 6 continues its upward movement, the intake port 8 and the exhaust port 9 are closed, thus compressing the mixture present in the combustion chamber 5. The compressed mixture is ignited by a spark plug 15. The expanding combustion gases drive the piston 6 downwards, whereby the outlet 9 is opened and the combustion gases can flow out.The amount of combustion air flowing in is controlled by the pivotable throttle valve 10a in the carburetor 10.

[0030] In the illustrated embodiment, a generator 16 is driven by the crankshaft 4. This generator is designed as a signal generator and, in particular, as an AC generator with an electrical output sufficient to supply electrical consumers. The induced AC voltage signals are fed to an ignition unit 18 via a single line 17. The ignition unit 18 is connected to the spark plug 15 via a high-voltage cable 25. The high-voltage cable 25 and the electrical line 17 are sufficient to establish the connection between the engine unit 19 and the ignition unit 18 for proper operation.

[0031] It can be advantageous to equip the generator with multiple windings or to design the coil with different taps for different loads. Ideally, at least two coils are provided, one of which supplies a first load and the other a second load. The circuits of the coils can be separate.

[0032] The ignition unit 18 is separate from the motor unit 19 and can be freely mounted at a suitable location on the motor unit 19 or on the housing of a device driven by the motor unit 19. The ignition unit 18 is connected to the generator 16 via a single signal line 17, through which the AC voltage signal from the generator 16 is supplied. The ignition unit 18 processes the AC voltage signal 18, deriving an angle information signal from it and also providing electrical energy for the various electrical consumers, such as the ignition unit 18, the carburetor heater 36, and other consumers 35.

[0033] The alternating voltage signal S, preferably continuous via the rotation of the crankshaft ( Fig. 3) The AC generator 16 supplies, on the one hand, an input unit 30 for energy conditioning and, on the other hand, a unit 33 for processing angular information. The input unit 30 thus processes the AC voltage signal S and provides the necessary electrical energy for operation to a high-voltage unit 31, which is connected to the spark plug 15 via cable 25. The electrical energy of the AC voltage signal S can not only supply the ignition unit 18 itself with the necessary energy; a carburetor heater 36 on the carburetor 10 can advantageously be operated via a consumer line. Further internal or external consumers such as a target laser or a lamp can be connected via terminals 35, or energy storage devices such as a battery can be charged, e.g., to supply power to the ignition unit 18. On the other hand, the input unit 30 processes the AC voltage signal S into an angular information signal W ( Fig. 6), which is fed via a decision rhombus 32 to an evaluation unit 33 or directly to an ignition timing control 34. The ignition timing control 34 advantageously consists of a microprocessor with corresponding peripheral components. The output signal of the evaluation unit 33 is also fed to the ignition timing control 34. The ignition timing control 34 controls the high-voltage unit 31 to trigger a spark at the spark plug 15 with precise angular accuracy. The control unit can also operate other functions, e.g., an injection valve for fuel injection or other mechatronic components.

[0034] The alternating current generator 16 used in the motor unit 19 is advantageously designed as a so-called claw pole generator, as is the case in Fig. Figure 2 is shown schematically. It essentially consists of a housing-mounted coil former 20, which is fixed to the crankcase 3 by means of mounting tabs 24. The coil 26 is enclosed by a total of twelve claws 27, with the claws 27 alternately engaging the coil 26 from one end and the other. The claws 27 form part of a magnetic circuit for the alternating magnetic flux.

[0035] In the illustrated embodiment, the rotor 21 is integrated into a fan wheel 28, which is fixed to the end of the crankshaft 4 and rotates with the crankshaft 4. The rotor 21 consists of a magnet ring 21 made up of twelve permanent magnets 23, which are evenly distributed around the circumference of the rotor with alternating poles N, S. A support ring 29 is used for this purpose, which can also be designed as a magnetic return ring. Due to the alternating polarity of the adjacent permanent magnets 23, an alternating magnetic flux passes through the coil 26 of the coil former 20 when the rotor 21 rotates, resulting in corresponding induced alternating voltage signals that are supplied to the input unit 30 in the ignition unit 18 via line 17.When mounting the coil former 20 on the crankcase 3 of the internal combustion engine 1, it may be advantageous to align the rotational position of the coil former 20 as a stator such that the induced voltage has a zero crossing when, for example, the exhaust port 9 is open, the piston 6 is at top dead center, or the intake port 8 is opened. An idealized voltage curve of an AC generator according to... Fig. 2 is in Fig. Figure 3 shows the voltage as normalized voltage U / Û and plotted against the rotational position of the crankshaft, i.e., against the crankshaft angle °KW.

[0036] The design of the AC generator 16 is adapted to one crankshaft revolution such that the period T of the AC voltage signal S corresponds to the nth part of a crankshaft revolution. In the exemplary embodiment according to Fig. 3, where n is preferably an integer greater than 2. Preferably, the number n lies between 5 and 8, particularly between 4 and 7. In the exemplary embodiment, the number n is chosen to be 6. It may be advantageous to also provide larger numbers up to a maximum of 12 or greater, which increases the number of zero crossings over one crankshaft revolution.

[0037] If the period T is defined as one-sixth of a crankshaft revolution, then the period T corresponds to 60°KW. Accordingly, one revolution of the crankshaft (360°KW) is divided into six crankshaft intervals I, II, III, IV, V, VI, as shown in the bar in Fig. 3 shown above and in Fig. 4 is shown as a pie chart.

[0038] Each pair of claws 27 of the stator or coil former 20, together with two permanent magnets 23, generates a complete alternating voltage wave with a positive and a negative half-wave, whereby the alternating voltage waves seamlessly connect to one another. This results in a solid curve accordingly. Fig. 3. Dividing the crankshaft into six intervals I to VI results in twelve zero crossings O. i of the alternating voltage signal S. Therefore, twelve zero intervals N can be defined. i e.g., define N1, N2, N3, etc. Each zero interval N i is defined by two consecutive, preferably adjacent, zero crossings O i and O i+1 of the alternating voltage signal S. The sequence of zero crossings O i corresponds to an angle information signal W ( Fig. 6), which is processed in the input unit 30 of the ignition unit 18. For each zero interval N iAn interval speed n is generated by the input unit 30. i calculated such that for each zero interval N i an interval speed n i is assigned.

[0039] In Fig. Figure 4 shows the assignment of the respective crankshaft angle intervals I to VI and zero intervals N1 to N12, as well as the zero crossings O1 to O12. Fig. Figure 4 shows that the distance between two zero crossings, e.g. O1 and O2, corresponds exactly to 30° crankshaft angle; from this relationship, the angular velocity ω of the crankshaft in the respective zero interval N can be directly determined. i can be derived. The zero crossings O iThe signals are thus evenly distributed over one crankshaft revolution. It may be sufficient to evaluate the AC voltage signal over only a portion of a crankshaft revolution, for example, between 120° crank angle before TDC and 120° crank angle after TDC. It would then also be sufficient to design a generator such that an AC voltage signal is produced only over this range.

[0040] The structural arrangement of the stator to the rotor is advantageously chosen such that the top dead center (TDC) of the piston directly corresponds to a zero crossing (O). i This is followed, preferably by approximately 15° crank angle later. It may be advantageous to position the top dead center (TDC) near or at the maximum of the signal S. Accordingly, the bottom dead center (BDC) of the piston will then be at approximately 195° crank angle.

[0041] In Fig. Figure 5 shows the voltage signal U of the AC generator 16 during operation of the internal combustion engine 1 over time t. The voltage amplitude and the intervals of the zero crossings are proportional to the rotational speed n. The zero crossings are N3 to N 12 are approximately load-independent, so the zero-crossing intervals are directly a suitable parameter for the rotational speed. To account for any potential load influence on the position of the zero crossings O i To further exclude, it may be useful to measure an electrical load connected to generator 16 in the area of ​​a zero crossing O i The load should generally be kept de-energized; it is only supplied with energy from the generator between two zero crossings. Because the generator is then unloaded, any potential inductive or capacitive signal shifts are eliminated. It has proven advantageous to interrupt the current flow for a period of approximately 5° before an expected zero crossing. ito approximately 1° KW after this zero crossing O i proven.

[0042] If the interval speeds n i over the intervals N i When plotted, the resulting rotational speed profile for a starting process is as follows Fig. 6. For one crankshaft revolution, in Fig. 6 the calculated interval speeds n1 to n 12 marked.

[0043] The rotational speed profile of the interval speeds forms the angle information signal W, which allows for a rotationally correct assignment of the mechanical crankshaft position to the AC voltage signal S. The number of angle intervals N determines this. iThe speed profile of the internal combustion engine 1 is highly pronounced. If the speed profile W is considered over at least one complete revolution of the crankshaft 4, various significant features can be filtered out, whereby a significant feature can be assigned to an operating parameter of the internal combustion engine 1. From the speed profile of the determined interval speeds n i In conjunction with the known design features of the internal combustion engine 1, a simple determination of the crankshaft angle position can be carried out. Regardless of the actual rotational angle °KW of the crankshaft 4, the speed profile W of the interval speeds n is determined as soon as its rotation begins. ievaluated to determine the actual mechanical crankshaft angle position. This is possible within the first crankshaft revolution, since the significant features of the speed curve, e.g., compression in the region of top dead center (TDC), the opening of the exhaust port 9, or the opening of the transfer port 14, occur within the fixed zero-point interval N. i are pronounced. Several different operating parameters of the internal combustion engine 1 can be determined using one and the same speed profile.

[0044] In order to achieve a rotationally correct assignment of the alternating voltage signal S to the mechanical crankshaft position, according to a first embodiment of the invention, the speed profile W of the interval speeds n i to a pronounced minimum speed n 12 scanned, with N being measured in the corresponding crankshaft angle interval 12 of the minimum rotational speed n 12The crankshaft angle position corresponds approximately to the position of piston 6 at top dead center (TDC). To determine the actual mechanical angular position of the crankshaft more quickly and precisely, the polarity of the voltage signal F can be adjusted within the crankshaft angle interval N. 12 additionally evaluated. Referring to the idealized representation in Fig. 3. The zero intervals N1 to N 12 The electronics of the ignition unit 18 can be easily distinguished, since the zero intervals N1, N3, N5, N7, N9 and N 11 have one positive half-wave and the other zero intervals N2, N4, N6, N8, N 10 and N 12 a negative half-wave.

[0045] Furthermore, if the rotational position of the AC generator 12, i.e. in the exemplary embodiment according to Fig. 2 the rotational position of the coil body 20 forming the stator is adjusted such that the zero crossing O 12Since the voltage signal S lies at the top dead center TDC of piston 6, there is a largely unambiguous assignment between the zero crossings N. i and the mechanical crankshaft angle position is possible.

[0046] It may be advantageous to adjust the rotational position of the stator 20 such that the crankshaft angle interval N 12 of the minimum rotational speed n 12 symmetrical to top dead center TDC, so that by a simple comparison of the adjacent interval speeds n 11 and n1, the minimum rotational speed, can be determined without significant computational effort. The following applies: n11>n12 <n1.

[0047] To create favorable conditions for a rapid assignment of the AC voltage signal S to the crankshaft at startup, it is advantageous to adjust the rotational alignment of the stator to the rotor so that a zero crossing O iof the voltage signal S immediately before the top dead center TDC of the piston, preferably about 15°KW before TDC.

[0048] The starting process of an internal combustion engine 1 according to Fig. Figure 1 also shows a characteristic rotational acceleration, which always occurs at equal intervals of the zero intervals N. i occurs. A reference curve R is derived from a large number of start-up processes according to Fig. Once the reference curve R is determined (8), the actual mechanical crankshaft angle position can be easily identified. For this purpose, the determined interval speeds are normalized (n). mom ) and with the reference speed n ref of the corresponding interval N i compared to the reference curve R. The difference between the normalized interval speeds n mOm (in ref(i) is used to calculate a cumulative error. The cumulative error calculated is then largely 0 if the actual rotational speed profile and the reference curve are similar or identical. Fig. Thus, the position of the piston 6, and therefore the rotational angle of the crankshaft 4, is reliably detected in the intervals L1, L2, L3, L4, and L5 because the total error is approximately 0. Accordingly, at the time of the total error (approximately 0), the ignition timing control 34 can initiate the ignition.

[0049] In a further embodiment of the invention, the rotational speed profile W can be differentiated accordingly Fig. 10 can be represented as a difference curve D. Advantageously, this is not a mathematical differentiation, as this is mathematically very complex. An approximate result can be obtained by evaluating the change in rotational speed per zero interval. The following applies: n=ΔαΔt⇒n'=Δn(i→i+1)

[0050] Since a zero interval extends over 30° crank angle (KW), Δn is determined by time measurement. The resulting difference curve D has a significant hook H in a corresponding interval of the crankshaft angle KW, which allows for an unambiguous assignment of the crankshaft angle. If the ignition unit 18 has assigned a unique mechanical crankshaft angle position to the AC voltage signal S, the actual crankshaft angle position can then be tracked by simply counting the zero crossings. Further evaluation of the speed profile W itself is unnecessary. The electrical AC voltage signal S is assigned to the actual mechanical crankshaft angle position with correct angular accuracy; the signal is locked in the correct angular position. At each zero crossing O iThe ignition unit 18 knows the actual mechanical crankshaft angle position, so that the diamond 37 can directly supply the processed angle information signal W to the ignition timing control 34. An evaluation of the angle information signal W for the purpose of assigning (locking) the AC voltage signal S to the actual mechanical crankshaft angle position in the evaluation unit 33 is therefore unnecessary. According to a further feature of the invention, an extrapolation of the crankshaft angle position is performed between two zero crossings, with each zero crossing O being used as the basis for calculation. i It is assumed that... It was determined that until the next zero crossing O is reached... i+1 Although angular errors do occur, these are in the range of approximately 1° crankshaft angle and will be corrected upon reaching the next zero crossing. i+1can be reset to zero. The direction of the angular error in the extrapolation provides information about the compression or expansion, with a maximum error occurring after complete combustion, i.e., at a point in time when the deceleration (due to compression) changes to acceleration (due to combustion).

[0051] In Fig. 11 shows that the angular error is clearly pronounced and allows an assignment to a crankshaft angle interval in the area of ​​the top dead center TDC of the piston 6, i.e. to the times T1 and T2.

[0052] In order to determine the actual rotational angular position of the crankshaft more precisely, the rotational position of the AC generator 16, i.e., the rotational angular position of the stator 20, can advantageously be provided such that a zero crossing O iThe voltage signal S is located in a rotational angular position of the crankshaft 4 that is approximately 40° crank angle before the ignition timing range, in particular 15° crank angle before top dead center (TDC). Preferably, the rotational alignment between the stator and the rotor of the AC generator 16 is adjusted such that a voltage maximum – in particular a positive one – is located at the top dead center (TDC) of the piston. In another configuration, a zero crossing O iimmediately before the ignition point of the internal combustion engine is advantageous. In a further development of the invention, the ignition unit 18 consists of separate assemblies 18a, 31, which form independent components. One assembly is formed by an electronic control unit 18a, such as a microprocessor or the like, and the other assembly by the high-voltage unit 31. This allows the control unit 18a to be arranged separately from the high-voltage unit 31 in a thermally favorable area of ​​the working device. An arrangement on or near a component of the engine unit 19 is advantageous. For example, the control unit 18a can be arranged on the mixture preparation device, such as the carburetor 10. The engine unit 19 is advantageously suspended together with the carburetor 10 in a housing of a working device via anti-vibration elements, with the carburetor 10 being advantageously suspended, for example, by means of a suspension system.An elastically designed channel 13a is elastically connected to the internal combustion engine 1. Arranging the control unit 18'a directly on the housing of the carburetor 10 has the advantage of effective vibration decoupling, since the carburetor 10 is decoupled from the housing of the working device via the AV elements and is vibrationally decoupled from the internal combustion engine 1 due to the elastic connection. This achieves a vibration-decoupled arrangement of the electronic control unit 18'a without the need to route the electrical connecting lines to the high-voltage unit 31 or to the generator 16 across the AV gap. A thermally favorable arrangement for the control unit 18'a has been found that is low in vibration and also low in dirt.

[0053] Alternatively, the control unit 18'''a can also be arranged on or near the crankcase 3, for example near the generator 16 below the cylinder 2. An advantageous position for the control unit 18''a is also on the part of the crankcase 3 that faces away from the cylinder 2, i.e., at the bottom of the crankcase 3, as shown in Fig. 1 shown.

[0054] In the exemplary embodiment according to Fig. In the embodiment shown, the AC generator 16 is configured as a star generator, i.e., as a generator 16 with radially arranged poles 42 in a star configuration. The coil former 20 of the stator 40 consists of a stack of individual laminations 41, the individual laminations 41 being axially stacked on top of each other. The lamination stack has individual, post-like coil supports that extend radially inwards to an outer circumference 44. The posts form individual poles 42 and serve as supports for induction coils 22, at least one of which is arranged on each post-like pole 42. In the illustrated embodiment, a total of 12 posts are provided, spaced apart from each other in the circumferential direction at an equal distance U, preferably 30°.

[0055] To fasten the stator 40, continuous axial fastening openings 48 are provided in two approximately opposing posts, which penetrate the plates 41 and serve to accommodate fastening screws with which the stator 40 can be fastened - e.g. to the crankcase 3 ( Fig. 1) - is fixed in a rotationally fixed manner. The posts with the mounting openings 48 are designed without coils. The stator 40 is advantageously cast, for which purpose a cylindrical base plate 45 is placed at the base of the post-like poles 42, projecting axially beyond the end faces of the laminated core. Correspondingly, the posts carry end plates 46 at their free ends, the axial length of which corresponds to the axial height of the base plate 45. The space between the base plate 45 and the end plates 46 is filled with casting resin or the like. This fixes the coils to the individual post-like poles 42 and secures them against mechanical damage.

[0056] The posts with the mounting openings 48 are selected such that, in the circumferential direction, four poles 42 are located between them on one side and six poles 42 on the other side. The sum signal of the interconnected coils 22 corresponds to the alternating signal S as described in Fig. 3 is shown.

[0057] The rotor 52 is - as in the embodiment shown in the following Fig. 2 - formed by a wheel body 50, which in the exemplary embodiment forms the fan wheel 51 of an internal combustion engine. On the side facing the stator 40, a receiving pot 55 is formed, into which a magnet ring 30 is inserted. This magnet ring is alternately magnetized as the north pole N and the south pole S at equal intervals A around its circumference. In this way, twelve permanent magnets 23 are formed around the circumference. Detent grooves 39 are provided on the end faces of the magnet ring 60 to ensure its rotational position in the receiving pot 55 of the rotor 52. The position of the magnet ring 60 relative to the position of the crankshaft is determined by these detent grooves 39.

[0058] In its assembled state, the one-piece magnet ring 60 lies with its inner circumference at a slight distance above the outer circumference 44 of the stator 40; the stator 40 is completely enclosed within the magnet ring 60. When the rotor 52 rotates, the alternating magnetization of the magnet ring 60 leads to an alternating flux in the poles 42, thereby inducing an alternating voltage signal S, as described in Fig. 3 and Fig. 5 is shown.

Claims

[1] Ignition device for an engine unit (19) with a two-stroke engine (1) in a portable, hand-held work device, [01] wherein the two-stroke engine (1) comprises a piston (6), a combustion chamber (5) with a spark plug (15) and a crankshaft (4) driven by the piston (6) to rotate, [02] with an inlet window (8) for supplying combustion air into the combustion chamber (5) and an outlet (9) for removing combustion gases from the combustion chamber (5) [03] and with an alternating current generator (16) driven by the crankshaft (4) which is attached to the engine unit (19) and which outputs successive alternating voltage signals (S) within one crankshaft revolution, [04] and with an ignition unit (18) which triggers an ignition spark at the spark plug (15) at a preselectable time, characterized by , [05] that the ignition unit (18) is designed as a separate assembly from the motor unit (19), [06] that the electrical alternating voltage signal (S) of the alternating current generator (16) is supplied to the ignition unit (18) as an information signal sufficient for the operation of the two-stroke engine (1), [07] that the alternating voltage signal (S) is supplied to a unit (30) for energy conditioning and to a unit (33) for conditioning information for controlling the two-stroke engine (1), [08] and that the information signal sufficient for the operation of the two-stroke engine (1) is an angle information signal (W) processed from the alternating voltage signal (W) for the rotationally correct assignment of the mechanical crankshaft angle position to the alternating voltage signal (S). [2] Ignition device according to claim 1, characterized by , that the alternating electrical voltage signal (S) of the signal generator (16) is supplied as the only information signal sufficient for the operation of the two-stroke engine (1). [3] Ignition device according to claim 1, characterized by, that the angle information signal (W) consists of successive zero crossings (O i ) of the alternating voltage signal (S). [4] Ignition device according to claim 3, characterized by , that the zero crossings (O i ) are evenly distributed over one crankshaft revolution. [5] Ignition device according to claim 3, characterized by , that the distance between two zero crossings is a zero interval (N1, N2, ... N i ) forms and for each zero interval (N1, N2, ...N i ) the interval speed (n1, n2, n i ) is determined to show that the interval speeds (n1, n2, n i ) depict a rotational speed profile, and that the rotational speed profile forms an angle information signal (W). [6] Ignition device according to claim 5, characterized by , that the speed profile is shown over at least one complete revolution of the crankshaft (4). [7] Ignition device according to claim 1, characterized by, that the processed angle information signal (W) is sampled for a significant feature and the significant feature is assigned to a known mechanical angular position of the crankshaft (4). [8] Ignition device according to claim 5, characterized by , that a zero interval (N1, N2, ... N i ) corresponds to the nth part of a crankshaft revolution, where n is an integer greater than 6. [9] Ignition device according to claim 8, characterized by that the number (n) is between 6 and 24, preferably equal to 12. [10] Ignition device according to claim 5, characterized by , that the rotational position of the AC generator (16) on the machine unit (19) and the top dead center (TDC) of the piston (6) are coordinated such that a zero interval (N i ) symmetrical to the top dead center (TDC) of the piston (6). [11] Ignition device according to claim 5, characterized by, that the rotational position of the alternating current generator (16) on the machine unit (19) and the top dead center (TDC) of the piston (6) are coordinated such that a zero crossing (O i ) of the signal (S) preferably lies about 15°KW before the top dead center (TDC) of the piston (6). [12] Ignition device according to claim 5, characterized by , that the rotational position of the alternating current generator (16) is provided such that a zero crossing (O i ) of a voltage signal (S) in a rotational angular position of the crankshaft (4) approximately before the ignition timing range, preferably immediately before the ignition timing range. [13] Ignition device according to claim 5, characterized by , that the speed profile of the interval speeds (n1, n2, ... n i ) is differentiated and the zero interval (N i ) with a significant hook (H) in the differentiated curve (D) is assigned a characteristic mechanical crankshaft angle position. [14] Ignition device according to claim 1, characterized by , that the alternating current generator (16) is designed as a claw pole generator or star generator. [15] Ignition device according to claim 14, characterized by , that the stator (20) of the generator (16) is fixed to the crankcase (3) and the rotating magnet ring (21, 60) is connected to a fan wheel (28, 51) of the two-stroke engine (1) in a rotationally fixed manner. [16] Ignition device according to claim 1, characterized by , that energy of the alternating voltage signal (S) is supplied to an electrical consumer, in particular a high-voltage unit of the ignition device, a heating device, a light source or the like. [17] Ignition device according to claim 16, characterized by , that a current flow through an electrical load connected to the AC generator (16) in the region of the zero crossing (O i ) of the alternating voltage signal (S) is prevented. [18] Method according to claim 16, characterized by, that a current flow through an electrical load connected to the AC generator (16) in an angular range of about 5° KW before the zero crossing (O i ) to about 1° KW after the zero crossing (O i ) is prevented. [19] Ignition device according to claim 1, characterized by , that the ignition unit (18) consists of a control unit (18a) such as a microprocessor or the like and a separate high-voltage unit (31). [20] Ignition device according to claim 19, characterized by , that the control unit (18a) is arranged separately from the high-voltage unit (31) in a thermally low-stress area of ​​the working device. [21] Ignition device according to claim 19, characterized by , that the control unit (18a) is arranged on or near a component of the motor unit (19). [22] Ignition device according to claim 18, characterized by , that the component is the mixture preparation device, preferably the carburetor (10). [23] Ignition device according to claim 21, characterized by that the component is the crankcase (3), preferably the part of the crankcase (3) facing away from the cylinder (2). [24] Method for processing an alternating voltage signal from an alternating current generator (16) driven by a shaft of an internal combustion engine (1) into an angle information signal (W) assigned to the rotating shaft (4) in a rotation-angle-correct manner, in an ignition device according to one of claims 1 to 23, characterized by , that the alternating current generator (16) is constructed such that the structurally predetermined distance between the zero crossings (O i ) of the alternating voltage signal (S) corresponds to an nth part of a complete wave revolution, where (n) is an integer such that the time interval between successive zeros (O i , O i+1 ) captured and for a zero interval (N i ) successive zero crossings (O i , Oi+1 ) an interval speed (n i ) is determined, and that the rotational speed values ​​of the interval rotational speeds (n1, n2, ... n i ) are plotted over the shaft angle (°KW) and represent a rotational speed profile that forms an angle information signal (W) for the mechanical rotational angle position (°KW) of the shaft (4). [25] Method according to claim 24, characterized by , that the determination of the zero crossing (O i ) with generator (16) unloaded. [26] Method according to claim 25, characterized by , that a current flow through an electrical load connected to the alternating current generator (16) at the time of the zero crossing (O i ) of the alternating voltage signal (S) is prevented. [27] Method according to claim 26, characterized by , that blocking the current flow through an electrical load over an angular range of approximately 5° KW before the zero crossing (O i ) to about 1° KW after the zero crossing (O i) continues. [28] Method according to claim 24, characterized by , that the speed profile is sampled to a speed minimum, whereby the speed minimum is approximately assigned to the rotational angle (°KW) at top dead center (TDC) of the piston position. [29] Method according to claim 28, characterized by , that the speed profile is compared with a reference curve (R) and, if there is a large degree of agreement with the reference curve (R), the specific rotation angle values ​​of the reference curve (R) are assigned to the phase position of the real speed profile. [30] Method according to claim 24, characterized by , that the rotational speed profile is differentiated and the difference curve (D) is compared with a reference curve (R). [31] Method according to claim 29, characterized by , that the comparison with the reference curve (R) is carried out using the sum error method. [32] Method according to claim 24, characterized by, that the actual mechanical crankshaft angle position (°KW) between two zero points (N i , N i+1 ) is determined by extrapolation.

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