US3736914A

US3736914A - Electronic ignition system for an internal combustion engine

Info

Publication number: US3736914A
Application number: US00160413A
Authority: US
Inventors: P Schmaldienst; G Brand
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1970-07-07
Filing date: 1971-07-17
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05
Also published as: DE2033484A1; SE362286B; GB1335137A; ES392965A1; AT309908B; JPS5228968B1; CH539201A; DE2033484B2; CA928376A; FR2117000A5

Abstract

A plurality of magnets rotated by the engine induces an alternating current voltage in a winding for charging the ignition capacitor, the discharge of the capacitor being controlled by a thyristor of which the control electrode is connected to a winding in which is induced, one each complete rotation of the magnets, a control voltage. Two neighboring magnets have extension pieces that cooperate with the core of the control winding to induce therein the control voltage, the remaining magnets being so positioned with respect to the core that during rotation these magnets induce no control voltage.

Description

Unite States atent [191 Schmaldienst et a1.

[ 1 June 5,1973

[75] Inventors: Peter Schmaldienst, Nurnberg; Giinter Brand, Stuttgart, both of Germany [73] Assignee: Robert Bosch Gmbl-l, Stuttgart, Germany 22 Filed: July 7, 1971 [2]] Appl. No.: 160,413

[30] Foreign Application Priority Data July 7, 1970 Germany ..P 20 33 484.3

[52] US. Cl ..123/l48 E, 123/149 D, 123/148 R, 123/148 S [51] Int. Cl ..F02d 1/00 [58] Field of Search ..123/148 E [56} References Cited UNITED STATES PATENTS 3,623,467 11/1971 Piteo ..l23/l48 E 3,630,185 12/1971 Struber ..123/l48 E 3,599,615 8/1971 Foreman... ..123/148 E 3,598,098 8/1971 Sohner ..l23/148 E 3,554,179 1/1971 Burson...... ..123/148 E 3,500,809 3/1970 Hohne ..123/148 E Primary ExaminerLaurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-Michael S. Striker [57] ABSTRACT A plurality of magnets rotated by the engine induces an alternating current voltage in a winding for charging the ignition capacitor, the discharge of the capacitor being controlled by a thyristor of which the control electrode is connected to a winding in which is induced, one each complete rotation of the magnets, a control voltage. Two neighboring magnets have extension pieces that cooperate with the core of the control winding to induce therein the control voltage, the remaining magnets being so positioned with respect to the core that during rotation these magnets induce no control voltage.

7 Claims, 3 Drawing Figures ELECTRONIC IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION The invention relates to an electronic ignition system for an internal combustion engine, the sparking of the one or more spark plugs being controlled by a control voltage that is induced in a control winding carried by a magnetic core and conducted to the control electrode of an electronic switch, such as a thyristor.

Among these electronic ignition systems of the prior art, it is known to provide a rotatable magnetic system, which comprises a plurality of magnets that, with respect to the axis of rotation, are radially polarized and are mounted on a hollow, cylindrical, short circuiting part. These magnets are spaced apart in the direction of the circumference of the cylindrical short circuiting part. The polarity of these magnets alternates, there being an alternating current winding carried by an iron core, in which winding an alternating current is induced when the magnets rotate. Two lines, each drawn from the axis of rotation through the center of a respective end face of the core, lie along different radii of the cylindrical short circuiting part, which latter is part of a cup-shaped body of rotation, which has an inwardly extending connecting hub.

Internal combustion engines that are provided with an ignition system of this kind are usually intended for modern light motorcycles, the current being provided by a flywheel magneto or by a flywheel generator magneto so as to avoid the necessity of having a battery. The aforesaid alternating current winding can be used, for example, to charge the ignition capacitor, which, by triggering the aforesaid electronic switch, can be discharged through the primary winding of a spark coil, the sparkplug being connected across the secondary winding of this coil. To power the lamps and the horn there is usually provided a second alternating current winding carried by another iron core. The same magnetic system induces an alternating current in the secnd winding. In order to obtain an alternating current voltage of sufficiently high frequency, the magnetic system must have as many magnets as possible. If these same magnets would be used to induce the control voltage in the aforesaid control winding, the control voltage would cause too many ignitions and at times that would damage the engine, since in most cases only a single ignition is required for each complete rotation of the magnetic system.

With these electronic ignition systems of the prior art, there is provided a further rotatable magnet that is moved past the magnet yoke carrying the control winding at the ignition point. This ensures that the spark plug is sparked only when the piston in the cylinder is sufficiently near to top dead center. To avoid troublesome leakage flux, this further magnet is enclosed by a magnetic shield, a fact that adds to the cost and complexity of the ignition system.

SUMMARY OF THE INVENTION An object of the invention is an electronic ignition system for an internal combustion engine that avoids a special magnet for obtaining the ignition control voltage. 1

Briefly, the invention consists of a magnetic system, the magnetic system including a plurality of permanent magnets spaced about a common axis and defining a cylinder, means for mounting the plurality of magnets free to be driven in rotation by the engine about this common axis, an electronic switch for permitting when conductive the production of an ignition causing spark, a stationary magnetic core located within the cylinder and having two spaced end faces located opposite said plurality of permanent magnets, the respective centers of said end faces lying in a common radial plane of the cylinder, a control winding carried by the magnetic core and connected to the switch for generating a control voltage to control the conductivity of the switch when the plurality of permanent magnets rotates, and wherein each magnet of this plurality of permanent magnets is polarized along a radius of the cylinder, successive magnets of the plurality of permanent magnets having alternating polarity, this plurality of permanent magnets including first and second neighboring magnets, the plurality of magnets excepting these first and second magnets being so positioned with respect to the magnetic core that no voltage is induced in the control winding when the plurality of magnets rotates, the first magnet including an extension of one pole, this one pole being positioned nearer to the two end faces when the first magnet is moved past the magnetic core than the other pole of the first magnet, the second magnet including an extension of the other pole, this other pole being the opposite of the one pole and being positioned nearer to the two end faces when this second magnet is moved past the magnetic core than the opposite pole of the second magnet, the two extensions projecting in opposed directions part way into the common space between the first and second magnets, the two extensions being spaced apart in a direction parallel to the common axis and in a predetermined rotational position of the plurality of permanent magnets being aligned with respective ones of the end faces of the magnetic core so as to induce in the control winding a full wave alternating current voltage when the plurality of magnets rotates, of which full wave one half wave is used as the control voltage, and a charging winding located within the cylinder for having induced therein, when the plurality of permanent magnets rotates, an alternating current voltage for charging the ignition capacitor.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view, partly cutaway, of the ignition system incorporating the improvement of the invention, the isometric view including a wiring diagram of the electric circuit;

FIG. 2 is an isometric view of one embodiment of the core for the control winding; and

FIG. 3 is an isometric view of a second embodiment of the core for the control winding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, the ignition system illustrated, which is intended for an internal combustion engine, now shown, comprises an ignition capacitor 11 of which one plate is connected to the ground rail 12 and the other plate is connected to the cathode of a rectifier 13. The anode of the rectifier 13 is connected to the terminal 14 of an alternating current winding 15, which serves as the charging winding, the other terminal 16 of this winding being connected to the ground rail 12. The ungrounded plate of the ignition capacitor 11 is also connected by the primary winding 17 of a spark coil 18 to the output electrode 19 of a thyristor that operates as an electronic switch 20, the reference electrode 21 and the control electrode 22 of the thyristor respectively being connected to the ground rail 12 and to to the cathode of a control diode 23. The anode of the control diode 23 is connected to the control terminal 24 of a control winding 25, the reference terminal 26 of which is connected to the grounded rail 12. The spark coil 18 also includes a secondary winding 27 across which is connected the spark plug 28, one end of the secondary being connected to the grounded rail 12.

The alternating current winding is mounted on an iron core 29, and is located along a chord of a circular path along which move the magnets M of a magnetic system M, the magnets being moved in the direction of the arrow P by the internal combustion engine. Each of the magnets M (three being shown, although there are four in this particular embodiment) is in the form of a shell, the outer faces of which are fixed to the inner wall 30 of a hollow, cylindrical, magnetic short circuiting part 32. This part is a component of a cup-shaped body of revolution 31, which is made of a magnetiferous material and incorporates a central, downwardly projecting, hub 34. The hub 34 incorporates a central bore 33, which accepts a shaft W that is rotated by the internal combustion engine.

The magnet M are radially polarized, as shown in FIG. 1, the north and sourth poles being designated by the respective reference letters N and S. The magnets M are spaced from one another a distance Z in the direction of rotation, the active poles (those poles nearest to the

ends

35 and 36 of the core 29) of successive magnets being of alternating polarity as they are moved by the end faces 35 and 36. The angle or defined between the radii r1 and r2, which begin at the axis of rotation O and pass through the centers a1 and a2 of these end faces, is so chosen that when a N pole passes by the end face 35 an S pole passes by the end face 36, or the reverse is true, or else when a spacing Z passes by the face 35 another spacing Z passes by the face 36. The alternating current winding 15 and the iron core 29 therefor are mounted on a circular plate 37, which is rigidly fixed to the internal combustion engine, and which incorporates a central opening 38 for the hub 34 and the shaft W.

Also fixed to the plate 37 is an iron core 39, which carries the control winding 25. The iron core 39 is so positioned with respect to the magnets M that the centers of the two end faces 40 and 41 of the core 39 lie in the same radial plane with respect to the axis 0.

The control voltage for the switch 20 is induced in the winding 25 by two neighboring magnets M1 and M2 of the magnets M. The magnets M1 and M2 have each a respective tongue-

like extension

42 and 43 of a respective active N and S pole, these extensions projecting into the common space Z between these two magnets. The

extensions

42 and 43 are spaced apart a distance b in the axial direction, just as are the

faces

40 and 41; and in a predetermined rotational position (shown in FIG. 1) of the magnetic system M they are aligned with, or cover, respective ones of the end faces 40 and 41, so that three edges of a

face

40 or 41 are aligned with three edges of a

respective extension

43 or 42.

In the preferred embodiment each of the active poles of the magnets M is covered with a magnetiferous plate L, the respective plates L1 and L2 for the magnets M1 and M2" having each a respective tongue F1 and F2, which extends at least approximately concentrically with the part 32. These tongues constitute, in a very simple manner, the

extensions

42 and 43.

In order to ensure that the ignition is suitably dependent on the instantaneous speed of the engine, it is desirable that at least one of the end faces 40 and 41 has an extension surface 44 (see FIGS. 2 and 3), which, in respect of the direction of rotation P of the magnetic system M, precedes the

end face

40 or 41. The extension surface 44 is incorporated by a magnetiferous extension piece 45, which is connected to the iron core 39, the cross section through which the magnetic flux is conducted being smaller than the cross section of the iron core 39.

A sufficiently large range of adjustment of the ignition timing is obtained by making the extension surface 44 contiguous with the end face, as shown in FIG. 2. The extension surface 44 is incorporated on that part of the extension piece 45 that tapers, in the manner of a crescent, in the direction opposite to that in which the magnetic system M rotates. In this case it is sufficient when the end face provided with the extension surface 44 is that end face (here 41) that is aligned with the extension 42.

If a sudden, stepped, ignition advance is desired when the engine speed exceeds a predetermined rpm, there can be provided a recess 47 between the

end face

40 or 41 and the extension surface 44, as shown in FIG. 3. In this embodiment it is advantageous if each of the end faces 40 and 41 is provided with an extension surface 44.

When the magnetic system M rotates, the following occurs. As the spacings Z are rotated past the end faces 35 and 36 of the iron core 29 that carries the altemating current winding 15, the changing flux in the core 29 induces an alternating current voltage in the winding 15. Those half waves of the alternating current voltage for which the diode 13 is conductive charge the ignition capacitor 11. Since the magnetic flux in the core 29 changes several times for each complete rotation of the magnetic system M, the ignition capacitor 11 is sufficiently charged to ensure a hot spark. If necessary, the

ignition capacitor 11 can be charged through a full wave bridge rectifier, so that each half wave of the voltage induced in the alternating current winding 15 is used to charge the ignition capacitor 11.

In the present case, the ignition system is intended for a single cylinder internal combustion engine, so that, if the magnetic system rotates at the same speed as does the engine, there will be one ignition for each complete rotation of the magnetic system. This is ensured, because during one complete rotation of the magnetic system the

extensions

42 and 43 are rotated past the end faces 40 and 41 only once, so that there is obtained only one complete cycle of alternating current voltage, that half wave thereof that is conducted by the diode 23 to the control electrode 22 of the switch 20 triggering the latter. The ignition capacitor 11 can now discharge through the primary winding 17 of the spark coil 18, so as to induce in the secondary winding 27 a high voltage spike that produces a spark in the gap of the spark plug 28, which spark ignites the compressed fuel-air mixture in the cylinder of the engine.

The extension piece 45 shown in FIG. 2 by reducing the steepness of the leading edge of the control voltage pulse broadens the range through which the ignition timing can be varied.

With reference to FIG. 3, the extension piece 45 causes a control voltage in the form of a full wave alternating current voltage when the

extensions

42 and 43 pass by the extension surfaces 44. At a low engine speed, the peak amplitude of this full wave is too small to reach the threshold voltage of the thyristor 20, so that there is ignition only when the

extensions

42 and 43 pass by the end faces 40 and 41. When the engine speed exceeds a predetermined rpm, there is a sudden, stepped, advance of the ignition, because the control voltage caused by the extension surfaces 44 now has a sufficient amplitude to trigger the switch 20.

If the internal combustion engine is intended, for example, for a motorcycle, the electric power for the lights and the horn can be obtained from the alternating current winding or from an additional alternating current winding carried by a separate core, in which the magnetic system induces, as it does in the winding 15, an alternating current.

In accordance with the invention, the number of magnets M can be more than four and/or more than one space Z can be provided with the

pole extensions

42 and 43.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits differing from the types described above.

While the invention has been illustrated and described as embodied in improvements in an electronic ignition system for an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptions should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended:

1. An arrangement in an electronic ignition system, having an ignition capacitor, for an internal combustion engine having at least one spark plug, comprising, in combination, a magnet system, said magnetic system including a plurality of permanent magnets spaced about a common axis and defining a cylinder; means for mounting said plurality of magnets free to be driven in rotation by the engine about said common axis; an electronic switch for permitting when conductive the production of an ignition causing spark; a stationary magnetic core located within said cylinder and having two spaced end faces located opposite the inner periphcry of said cylinder, the respective centers of said end faces lying in a common radial plane of said cylinder; a control winding carried by said magnetic core and connected to said switch for generating a control voltage to control the conductivity of said switch when said plurality of permanent magnets rotates, and wherein each magnet of said plurality of permanent magnets is polarized along a radius of said cylinder, successive magnets of said plurality of permanent magnets having alternating polarity, said plurality of permanent magnets including first and second neighboring magnets, said plurality of magnets excepting said first and second magnets being so positioned with respect to said magnetic core that no voltage is induced in said control winding when said plurality of permanent magnets rotates, the first magnet including an extension of one pole, said one pole being positioned nearer to said two end faces when said first magnet is moved past said magnetic core than the other pole of said first magnet, the second magnet including an extension of the other pole, said other pole being the opposite of said one pole and being positioned nearer to said two end faces when said second magnet is moved past said magnetic core than the opposite pole of said second magnet, the two extensions projecting in opposed direction part way into the common space between said first and second magnets, said two extensions being spaced apart in a direction parallel to said common axis and in a predetermined rotational position of said plurality of permanent magnets being aligned with respective ones of said end faces of said magnet core so as to induce in said control winding a full wave alternating current voltage when said plurality of permanent magnets rotates, of which full wave one half wave is used as the control voltage; and further comprising a charging winding located within said cylinder for having induced therein, when said plurality of permanent magnets rotates, an alternating current voltage for charging the ignition capacitor.

2. The arrangement as defined in claim 1 further including a respective magnetiferous plate covering that pole of each magnet of said plurality of permanent magnets that is positioned nearer to said end faces of said magnetic core when the respective said magnet passes by the latter during rotation of said plurality of permanent magnets, the respective plate of said first and second magnets having a tongue that comprises said extension, the surfaces of the two tongues at least approximately defining part of a common cylindrical surface that is located within said cylinder and having as its axis said common axis.

3. The arrangement as defined in claim 1, further including a magnetiferous extension piece means incorporating a face that is positioned opposite said plurality of magnets for extending the surface area of at least one of said end faces of said magnetic core in the direction opposite to the direction of rotation of said plurality of permanent magnets, said extension piece being physically connected with said magnetic core and having a cross section smaller than that of the latter.

4. The arrangement as defined in claim 3, wherein said face of said extension piece means is contiguous with said one end face, said face of said extension piece means tapering in the direction opposite to that of the rotation of said plurality of permanent magnets.

6. The arrangement as defined in claim 4, wherein said one end face is that face which is aligned with that said extension of a pole that causes the control voltage.

7. The arrangement as defined in claim 5, wherein said extension piece means includes a respective extension for each of said two end faces of said magnetic COI'C.

Claims

1. An arrangement in an electronic ignition system, having an ignition capacitor, for an internal combustion engine having at least one spark plug, comprising, in combination, a magnet system, said magnetic system including a plurality of permanent magnets spaced about a common axis and defining a cylinder; means for mounting said plurality of magnets free to be driven in rotation by the engine about said common axis; an electronic switch for permitting when conductive the production of an ignition causing spark; a stationary magnetic core located within said cylinder and having two spaced end faces located opposite the inner periphery of said cylinder, the respective centers of said end faces lying in a common radial plane of said cylinder; a control winding carried by said magnetic core and connected to said switch for generating a control voltage to control the conductivity of said switch when said plurality of permanent magnets rotates, and wherein each magnet of said plurality of permanent magnets is polarized along a radius of said cylinder, successive magnets of said plurality of permanent magnets having alternating polarity, said plurality of permanent magnets including first and second neighboring magnets, said plurality of magnets excepting said first and second magnets being so positioned with respect to said magnetic core that no voltage is induced in said control winding when said plurality of permanent magnets rotates, the first magnet including an extension of one pole, said one pole being positioned nearer to said two end faces when said first magnet is moved past said magnetic core than the other pole of said first magnet, the second magnet including an extension of the other pole, said other pole being the opposite of said one pole and being positioned nearer to said two end faces when said second magnet is moved past said magnetic core than the opposite pole of said second magnet, the two extensions projecting in opposed direction part way into the common space between said first and second magnets, said two extensions being spaced apart in a direction parallel to said common axis and in a predetermined rotational position of said plurality of permanent magnets being aligned with respective ones of said end faces of said magnet core so as to induce in said control winding a full wave alternating current voltage when said plurality of permanent magnets rotates, of which full wave one half wave is used as the control voltage; and further comprising a charging winding located within said cylinder for having induced therein, when said plurality of permanent magnets rotates, an alternating current voltage for charging the ignition capacitor.

5. The arrangement as defined in claim 3, wherein said extension piece means incorporates a recess that extends in the direction away from said plurality of magnets, said recess being positioned between said face of said extension piece means and said one end face.

7. The arrangement as defined in claim 5, wherein said extension piece means includes a respective extension for each of said two end faces of said magnetic core.