DE2030878A1 - Ignition system for two-stroke internal combustion engines - Google Patents

Description

RE. .Phelon Company, Inc.,

East Longmeadow ', Mass. (V.St.A.)

Ignition system for two-stroke internal combustion engines

The invention relates to ignition systems for two-stroke internal combustion engines, in particular to an ignition system in which any possibility of reverse running of the internal combustion engine equipped with it is excluded.

The principles of the invention can be applied in various ways Types of two-stroke internal combustion engines both large and large small dimensions and with one or more cylinders. The invention is particularly suitable for use in relatively small single cylinder machines of the The kind commonly used to drive lawn mowers, Chainsaws and similar tools are used, and they is explained below in connection with such an internal combustion engine. There are already various, electrical Proposed triggered ignition systems for such internal combustion engines and has been used to create the earlier more common mechanical To replace breaker systems. One common type of such ignition system is commonly referred to as a capacitor discharge system denotes and uses a capacitor that during

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Each work cycle of the machine is charged by feeding devices connected to it and then via a Step-up transformer is discharged to ignite the spark plug to cause. The discharge is controlled by a trigger signal that is supplied by a trigger coil in which a trip signal is induced by a flux-changing element which is produced by a rotating part of the machine will be carried. In two-stroke internal combustion engines that are equipped with a capacitor discharge ignition system or with another electrically triggered ignition system, it is sometimes it has been possible that when the machine is started, it accidentally moves in the opposite direction and starts up such reverse run continues. This reverse run can in turn damage the tool driven by the machine cause and / or a dangerous situation for the Bring about the person using the tool,

The object of the invention is therefore to provide a device which inevitably enables the possibility of such an accidental reverse run turns off.

In the drawings show:

1 shows a vertical section through the flywheel of an engine equipped with the ignition system according to the invention, the flywheel being part of this ignition system;

Fig. 2 is a vertical section along line 2-2 in Fig. 1;

FIG. 3 is a circuit diagram showing the ignition system according to FIG illustrated electrical components used;

BUg. 4 is a schematic diagram showing the positions of the Trip stator and the two pole pieces of the flywheel at the point in time in which the trip during the

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fast forward rotation of the associated motor takes place;

Pig, 5 a representation similar to FIG. 4, but with the mutual Location of parts illustrated at the time the triggering during slow forward movement the associated engine is taken;

6 is a view similar to FIG. 4, but with the mutual Positions of the parts illustrated at the time the trip can be taken during the slow reverse rotation of the motor;

Fig.7 is a schematic diagram illustrating the various points at which the trip is related takes place with the work cycle of the engine;

8 shows a vertical partial section similar to the representation in 1, but showing another form of flywheel used in place of that shown in FIG can.

9 is a perspective view showing the insert pole piece in the flywheel of FIG t> illustrates the.

Fig. 10 is an enlarged vertical sectional view taken along the line 10-10 of Fig. 8 and

11 shows an enlarged section along the line 11-11 Fig. 8.

Figures 1, 2 and 3 illustrate an electrically triggered ignition system according to the invention and for use with a single-cylinder two-stroke internal combustion engine. This system is a capacitor discharge system, in which the capacitor is charged and discharged during each cycle of the engine to produce the spark

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at the spark plug, it should be noted, however, that this ignition system was chosen only as an example and that the feature of the backflow prevention, which forms the basis of the invention, at least in terms of its more general Correlations can be applied just as well to other release ignition systems for two-stroke engines.

1 and 2 show the mechanical parts of the ignition system, the reference numeral 10 denoting a flywheel-like rotor, which is mounted on the crankshaft 12 of the associated engine 13 so that it is in synchronism with the running of the Engine rotates. A main magnet unit 15, which has a permanent magnet 14, is embedded in the edge of the rotor 10 and comprises two pole pieces 16 having spaced apart pole faces 18 of opposite magnetic polarity are provided on the outer circumference of the rotor. A stator core 20, which has two legs 22 is arranged in the vicinity of the rotor 10 and carries a generator coil 24 on one of its Leg. During each revolution of the rotor 10, the magnet unit 15 is therefore guided past the two legs of the stator 20 and creates a changing magnetic flux through the stator core, which in turn creates a voltage in the generator coil 24 induced. This voltage is used as the energy source for igniting the associated spark plug in below used as described.

The timing of ignition of the spark plug is controlled in the ignition system according to FIGS. 1 to 3 by a trigger coil 26, which also cooperates with the rotor 10, and a trigger signal is induced in it during each revolution of the rotor. The tripping coil 26 ¹ is mounted on one of the legs of the stator provided with two legs 28, which is arranged within the rotor ring, the stator 28 of a magnet-Pennanent

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30 and two legs 32 and 33 made of magnetic material. The two legs 32 and 33 extend after on the outside in the direction of the rotor ring and have end faces, which interact with a flux-changing part or pole piece 34, which is embedded in the rotor rim and has a pole face 36 of a circumferential length which is approximately the same is the maximum distance between the end edges of the pole faces of the stator legs 32 and 33. Accordingly go during each Circulation of the rotor 10 of the pole piece 34 on the trip stator 28 passes and induces a changing flow in it, the a trigger signal generated in the trigger coil 26 which is used to control the timing of ignition of the spark plug.

As indicated by the arrows in FIG. 1, the rotor 10 runs during normal forward running of the motor according to FIG. 1 in Clockwise around, and the mutual position of the main energy generating device and the trigger signal generating means is selected so that that of the main power generating means generated signal for powering the ignition of the Spark plug is generated before the trigger signal, which is used to control the timing of ignition. In detail shows Fig. 1 shows the rotor in the position it assumes when the Main power signal generated in the power generation coil 24 was, roughly at the midpoint of its file shape whose first half is used to feed the spark the spark plug is used in the manner described below is, the main magnet device 15 with the stator 20 flees. In this position of the rotor, the trip pole shoe 34 is at a considerable angular distance from the trip stator off and does not generate a trigger signal in the trigger coil 26 until the part of the waveform generated in the generator coil 24, that is used to supply the spark is completely terminated is.

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The electrical circuit and the components of the ignition system, the mechanical relationships of which are illustrated in FIGS. 1 and 2, are shown in FIG. According to this, the main generating coil 24 is connected via a capacitor 36 and a diode 40 to another diode 42 which is connected in parallel to the diode 40, the two diodes 40 and 42 being polarized so that the capacitor 38 is only charged when when the voltage induced in the generator coil 24 has one polarity. That is, when the magnet unit 15 passes the stator 20, a voltage waveform is induced in the generator coil 24 which is first of one and then of the opposite polarity, and only the part of the wave which has one polarity becomes the charge of the capacitor 38 is used. The latter is also connected to the primary coil 44 of a step-up transformer 46, the secondary coil 48 of which is connected to the spark plug 50. In the circuit between the capacitor 38 and the primary winding 44, a silicon controlled rectifier 52 is connected, the anode and cathode terminals of which are connected in series with the capacitor and the primary winding. The trigger coil 26 is connected between the ignition electrode and the cathode electrode of the controlled silicon rectifier 52 and controls the conductive state of the controlled silicon rectifier by the trigger signal induced in it, so that the time of the discharge of the capacitor 38 through the primary winding 44 is determined and thus the time of ignition of the spark plug 50. '-

In the normal operation of that shown in Figs Ignition system, with the motor and the rotor moving in the forward direction move, the magnet unit 15 first goes to the stator 20 passes and induces a in the generator winding 24 S4 Voltage that charges capacitor 38. Some time after this charge, the trip coil 34 on the legs 32 and goes

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33 of the trip stator 28 and induces a trip signal in the trip coil 26, which the controlled silicon rectifier switches to the conductive state, whereof the Capacitor 3B is discharged through the primary winding 44 of the step-up transformer and a high voltage in the secondary winding 4ö is generated which indicates the occurrence of a spark at the Spark plug 50 caused. If the Polsichuh 34 is different from the The trip stator is moved, a reverse voltage in the tripping coil 26 induces and a reverse voltage to the anode and cathode terminals of the controlled silicon rectifier applied, which is the result of a resonance between the capacitor 3ü and the winding 44, so that the controlled silicon rectifier is inevitably switched to a non-conductive state and thereby the operation is prepared in the following work cycle.

The illustrated design of the trigger signal generating device is designed so that an automatic pre-ignition

is achievable, thereby determining the time of occurrence of the spark is brought forward depending on an increase in engine speed. That means that during the slow run of the motor tripping occurs near the point at which the pole piece 34 approaches the rear stator leg 33, and that during the .Schnellaufs the triggering happens at the point at which the pole piece 34 is the front stator leg 32 approaches, with the ignition at the intermediate Points for the intermediate speeds takes place.

According to the invention, the ignition system further includes means which prevents the motor from operating in the reverse direction in the event that it by any accident or accident Carelessness in the reverse direction was started.

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According to Fig. 1, this device has the form of a second, the flux changing portion or pole piece 54 embedded in the rim of the rotor 10 for cooperation with the trip stator 28 is. The second pole piece 54 is designed to match the first pole piece 34 and so zn the other parts of the System arranged that he normal operation of the engine in the Forward running does not interfere and furthermore so that a trigger signal through it while running the motor in the reverse direction is generated in the trip coil 26 at such a time occurs in the work cycle of the engine that the accompanying ignition of the spark plug the further reverse rotation of the engine unsupported.

Referring to Fig. 1, the first consideration is the effect of the second pole piece 54 during normal forward motion of the motor determine that during each revolution of the rotor 10, the main magnet unit 15 first passes the stator 20 and a signal generated in the generator coil 24 that the capacitor 38 charges. The first pole piece 34 then passes the trip stator 28 and is induced in the trip coil 26 Trigger signal that the spark plug 50 is controlled by switching on the Silicon rectifier 52 ignites in the conductive state. This ignition of the spark plug removes the charge the capacitor 38. The second pole piece 54 then passes the trip stator 28 and induces a further trip signal in the trip coil 26. At this point in time, however, the trip signal has due to the discharged state of the capacitor 38 no effect and no additional spark is created on the spark plug.

If one now considers the mode of operation of the ignition system according to 1, 2 and 3 during the random backward movement of the rotor 10, this movement in the counterclockwise direction according to FIG Fig. 1 takes place, it follows that the main magnet unit

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15 first passes the stator 20 and a voltage signal induced in the generator coil 24, which charges the capacitor 38. When the rotor then continues to move in the reverse direction, the second pole piece 54 goes ahead of the pole piece 34 only past the trip stator 28 and induces a trip signal in the trip coil 26, which switches the controlled silicon rectifier 52 into its conductive state and the Capacitor 38 discharges through primary winding 34, whereby the Ignition of the spark plug 50 is caused. As in the Further explained in each individual case, the ignition of the spark plug is timed so that it occurs at one point in the engine work cycle takes place, which does not allow a further backward movement to be supported. When the rotor 10 is further in the reverse Moving direction, the pole piece 34 first goes to the trip stator 28 over, but because of the now discharged state of the capacitor 38, this causes it in the release coil 26 induced signal no ignition of the spark plug.

Fig, 4, 5, 6 and 7 show in more detail the mutual angular spacings and dimensions of the various parts of the triggering device and the points at which the spark plug is ignited in its relation to the engine operating cycle for comparable $ different speeds and directions of rotation of the rotor 10 .

If one looks first at Fig. 4, this shows the mutual Positions of the trip stator 28 and the two trip pole shoes 34 and 54 at the time of ignition during high-speed running of the associated motor in the forward direction. In detail finds the ignition of the spark plug 50 while the Rotor in the forward direction approximately in the position illustrated in Fig. 4, in which the leading edge 56 of the Release pole shoe 34 begins, the leading edge 58 of the front Stator leg 32 to drive over. In Fig. 4, the line 60 indicates the position of the leading edge 56 of the pole piece 34 when the

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associated motor 13 is in its top dead center position. It can therefore be seen from Fig. 4 that the ignition of the ignition plug takes place 30 ° before top dead center during the fast forward rotation of the rotor. This angular position, at which ignition takes place during high-speed running, can be varied depending on the design of the associated engine for which the ignition system is used, and this particular angular position for ignition at high-speed, as well as the other angular relationships shown in Fig 1 to 7 shown . are only chosen as an example. In the example shown, however, it should be noted that each of the pole faces of the legs 32 and 33 of the stator 28 has a

O
7 and are separated from one another by a gap of 13 °, so that a distance of 27 between the front edge 58 of the front leg 32 and the rear edge 62 of the rear leg 33 results. The two pole pieces 34 and 54 each have a pole face of approximately 27 ° extension in the circumferential direction and the distance between the front edge 56 of the pole piece 34 and the rear edge 64 of the pole piece 54 is 122 °.

If one now looks at FIG. 5, this shows the mutual Positions of the trip stator 28 and the Polachuhe 34 and 54 at the time of ignition during slow forward running of the engine. During such a slow forward run takes place in particular, the ignition of the spark plug 50 takes place in the rotor position illustrated in FIG. 5, with the leading edge 56 of the tripping pole shoe 34 begins to run over the front edge 66 of the rear tripping stator leg 33. As from FIG. 5, the ignition therefore takes place when the associated motor is 10 ° away from its top dead center is.

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Fig. 7 shows schematically the work cycle of the associated Motor 14, at least in terms of timing the opening and closing of the exhaust and intake valves and the time of ignition of the spark plug within such an operating cycle. In this figure, the Line 60 the top dead center position of the motor and line 69 the bottom dead center position of the same. The strip 70 means the state of the intake valve during a full power stroke and the strip 73 in the same way means the state of the exhaust valve during a full power stroke. In each of the two strips 70 and 72 a significant hatched part the time period during which the associated valve is closed and the non-hatched part the time segment during which the associated valve is open. Considered the inlet valve is thus illustrated as by the strip 70, so it can be seen that the inlet valve from the top dead center position to reaching a point 110 ° beyond of top dead center is closed and that it is then opened and remains open until a point 110 ° before top dead center is reached again, at which it is again is closed. The outlet valve remains in the same way closed when moving from top dead center until it reaches a point that is 95 ° before top dead center, and then opens and it stays open until a point is reached that is 95 lies before top dead center, at which it closes again will.

In Fig. 7, line 74 indicates the point at which ignition the spark plug takes place during the slow forward movement, this point being 10 ° before top dead center, as in 5 can be seen. Line 76 represents the point at which the ignition takes place during the fast forward run, whereby this point is 30 ° before top dead center, as shown in FIG. 4 evident.

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When the rotor is moved in the reverse direction 10 and containing no ^r second pole piece 54, a trigger signal is in the ^■! Trigger signal coil induces which occurs some time after top dead center, and although this timing is not suitable for good engine operation, it could be sufficient to keep the engine running. Therefore, to prevent this possibility, the second pole piece 54 is arranged so that, during reverse travel, the trip signal it generates occurs before that of the pole piece 34 and at a time in the duty cycle of the motor when it cannot sustain its operation.

According to FIG. 7 and assuming that the engine is now _{rotating in the reverse t A} , o.dex counterclockwise direction, it will be understood that most two-stroke engines will not work when the ignition timing is around ^; is more than about 40 before top dead center, the line 78 in FIG. 7 representing this 40 ° division. According to the invention, therefore, the second pole piece 54 is arranged so that, during reverse rotation and at the low crankshaft speeds which occur, a trigger signal is caused to be generated sufficiently before 40 ° before top dead center, as represented by line 78 , occurs. Any timing of the spark that is prior to 40 before top dead center (and of course well behind top dead center) is sufficient to prevent the rotor from continuing in the reverse direction and thus enables the general objects of the invention to be achieved. However, the timing is preferably selected so that the ignition takes place when the exhaust valve is open, so that any combustion that occurs is deflated through the exhaust valve without exerting force on the engine piston. Although, in accordance with this preferred embodiment, the ignition can take place in the cycle at any point where the exhaust valve is open, it is

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even more advantageous if the timing is such that the Ignition takes place while the exhaust valve is open, but that The inlet valve is closed, so that no refluxing through the inlet valve is possible during combustion Therefore, the preferred period of time during which the trigger occurs during the reverse run is the one between the Point 80 at which the inlet valve is during the backward movement to close to the top dead center, and the point 82 at which the exhaust valve during the backward movement to the top Dead center closes.

The relative angular spacing of the various parts shown in detail in FIG. 4 causes ignition to occur during reverse travel, which occurs within the desired period of time during which the exhaust valve is open and the intake valve is closed. Fig. 6 shows in more detail the relative positions of the illustrated parts at the time of ignition during slow reverse rotation of the engine. In this case, the ignition takes place when the now foremost edge 64 of the pole piece 54 begins to drive over the now foremost edge 84 of the now rear stator leg 32. At this point in time, the reference edge 56 of the pole piece 34 is 100 ° from the top dead center, as indicated by the line 60. According to FIG. 7, the ignition takes place at the point indicated by the line 86, which lies between the points 80 and 82 as desired. Accordingly, it will be seen from Fig. 7 that if the engine is accidentally started in reverse direction causing the engine and rotor to slow down, the second trip pole piece 54 will pick up the spark plug at the point indicated by line 86 Can ignite point at which the release valve is open and the inlet valve is closed, so that any combustion that takes place, through the release

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seventil deflagrates without acting on the piston and without backfire through the inlet valve, and that therefore the engine no service whatsoever is supplied that would enable it to function such backward movement so that it stops immediately.

In the mechanical construction of that illustrated in Figs Rotor 10, the two tripping pole shoes 34 and 54 are designed in the form of separate inserts made of magnetic material, which are separated from each other in the ring of the Rotor are embedded during the casting of the same, the rotor except for the various embedded therein Inserts made of aluminum or other non-magnetic cast material consists. The inserts 34 and 54 initially extend radially inwards towards the axis of the ring, beyond the points that will eventually come from their pole faces are taken, the latter by machining the inner surface of the rotor ring on it to make them exactly concentric and set to a certain radius. This form of the river changing However, use is not essential to the broader aspects of the invention. The two river-changing, Parts used in connection with the trip stator can, if desired, be different from those of the input λ sentences 34 and 54 have different shapes.

For example, Figures 8-11 show another shape of the flux changing portion for the trip stator. In these pictures the rotor is illustrated at 90. It corresponds to that according to FIGS. 1 and 2. Or can correspond to it, apart from the fact that it contains a different design of the part that changes the triggering flow. in the individually, the two flow-changing parts 92 and 94, which correspond to parts 34 and 54 in FIG. 1, are part of one

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single insert 96, which is shown alone in FIG. Parts 92 and 94 are similar to parts 34 and 54 in Fig. 1, apart from the fact that they are connected by a curved section 98 consisting of one piece with them, of the two parts 92 and 94 in a precise mutual angular position specifies. As best seen in Figs. 10 and 11, portions 92 and 94 extend into the disc of rotor 90 so that connecting portion 98 of the insert 96 is arranged within the disc 100 and therefore is located in a remote, hidden position is located at which it has little or no effect on the function of the two parts 92 and 94 with respect to the trip stator 28.

Thanks to the connecting section 98 that connects the two parts 92 and 94 connects, any difficulty in determining the exact angular position of the two parts with respect to one another becomes apparent avoided during manufacture of the rotor 90, it being only necessary to remove the one part 96 prior to forming or Bring the casting process to the right place.

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Claims (1)

- 16 claims : ( 1. / Ignition system for two-stroke combustion engines with at least one spark plug and a rotating part rotating synchronously with it, characterized by the combination of a trigger coil (26), a device connected to it for controlling the ignition of the spark plug (50) depending on one in the trip coil (26) generated trip signal »a first flux-changing part (34), which is carried by the rotatable part (10), for generating the trip signal in the trip coil (26) as the rotatable part (10) revolves, and on the the latter is arranged so that the point in time of the trigger signal induced by it in the trigger coil (26) during the forward running of the internal combustion engine is determined so that the ignition of the spark plug (50) is caused at such a point in time in the working cycle of the internal combustion engine that the forward running the same is maintained, and a second, also carried by the rotatable part (10), flow-changing part (54) r generation of a release signal in the release coil (26) when the rotatable part (10) rotates, the second flux-changing part (54) being arranged on the rotatable part (10) in such a way that the time of the release in the release coil (26) induced trigger signal is determined during the reverse running of the internal combustion engine so that it causes the ignition of the spark plug (50) at such a point in time in the work cycle of the internal combustion engine that its reverse running is not maintained. 2. Ignition system according to claim 1, - g e k e h η draws t by a main generating device (14, 16, 24, - 17 - 00985 2/166 20) for generating the for igniting the spark plug (50) required power, which also previously rotated Part (10) carried part (14) comprises. 3 · Ignition system according to claim 2, characterized by a to the main generating device (14, 16, 24, 20) connected capacitor (38), which is charged during each revolution of the rotatable part (10) by a device (46) connected to the capacitor (38) for generating a spark on the spark plug (50) as a result of the discharge of the capacitor (38) through it and through an electronic one Switching device (52) connected between the capacitor (38) and the spark generating device and with the trip coil (26) for controlling the time of the capacitor discharge by the spark-generating device is coupled therethrough under the effect of the release signal generated by the release coil (26). 4. Ignition system according to claim 1, characterized in that g e k β η η-z ei c h η e t, d aß the second flow-changing Part (54) is arranged on the rotatable part (10) so that that the time of the Internal combustion engine through it induced Aualösignalals so is determined that the ignition of the spark plug (50) to a such point in time in the work cycle of the internal combustion engine is caused, which is more than 40 ° before top dead center of the working cycle. 5. Ignition system according to claim 1, characterized in that that the second river changing ' Part (54) is arranged on the rotatable part (10) so that the time of it in the release coil (26) while the internal combustion engine is running backwards - 18 - 009852/1669 BAD original adorned trigger signal is determined so that the trigger signal causes the ignition of the spark plug (50) within the period during which the exhaust valve of the Internal combustion engine is in the open state 6, ignition system according to claim 5, characterized in that the arrangement is made so that the ignition of the spark plug (50) within the period takes place, during which the exhaust valve of the Brennaas engine is in the open and / intake valve is in closed state, 7. Ignition system according to claim 1, characterized by a trip stator (28, 30, 32, 33), dtr a permanent magnet (30) and two stator legs (32, 33), on one (33) of which the trip coil (26) is attached, the stator legs (32, 33) to extend in the direction of the rotatable part (10) and the first (34) and second flow-extending parts Part (54) are arranged on the rotatable part (10) so and at such an angular distance that ei · one after the other run past the release indicator (23, 30, 32, 33) so that Each of them during each revolution of the rotatable part (10) in the release coil · (26) »in Aual8e # own * l 8. Ignition system according to claim 7 , characterized in that the rotatable part (10) consists predominantly of a non-magnetic material and the first (34; 92) and second flux-changing part (54; 94) pieces of magnetic material included, which are carried by the rotatable part (10). 9. Ignition system according to Claim 8, characterized in that the two pieces of magnetic Material one rate (92) and the second one that changes the flow - 19 -009852/1669 ^BAD Part (94) included, which are made of one piece with a thin section (96, 98) of magnetic material and are connected by it, which defines the mutual inclination of the two parts (92, 94) precisely and apart of the area of the trip stator (28) is arranged. Wb / Pe; -w. 22 341 009852/1669