Signal source in use for a breakerless ignition system for an internal combustion engine

Abstract

A signal source for use in a breakerless ignition system for an internal combustion engine provided outside a flywheel of a flywheel type magneto generator, but cooperating with at least one of a plurality of permanent magnets in said magneto generator. The signal source comprises magnetically conducting means having one end magnetically connected to the one magnet at the pole piece thereon and the other end exposed at the outer periphery of the flywheel magneto generator. The signal source also comprises signal coil means magnetically associated with the exposed end of said magnetically conducting means whereby electric signals are generated from said signal coil means with rotation of said magneto generator.

Description

FIELD OF THE INVENTION

This invention relates generally to a signal source in use for a breakerless ignition system for an internal combustion engine.

BACKGROUND OF THE INVENTION

A breakerless ignition system for an internal combustion engine is well known which comprises a semi-conductor switching element, for example a thyristor disposed in a primary circuit of an ignition coil for controlling a primary current through the ignition coil by opening or closure of the switching element in time with ignition point of the engine. A capacitor discharge type ignition system is typically employed. Such ignition system is provided with a signal source supplying the semi-conductor switching element with a control signal in synchronism with rotation of the engine. In general, the signal source comprises a signal coil or coils disposed within a magneto generator in cooperation with magnetic field thereof. However, due to various coils, such as generating coil or coils for charging a capacitor in the capacitor discharge type ignition system and lighting coil or coils disposed within the magneto generator, it is practically difficult to provide within the magneto a space to mount the signal coil or coils therein. In particular, the breakerless ignition system for a multi-cylinder internal engine requires a plurality of signals, which causes the signal coil design to be complicated, resulting in that assembly of the signal coils is troublesome. In addition, the signal coil or coils disposed within the magneto tend to generate additional signals as well as control signal during one complete revolution of the magneto generator, with the number of the signals determined by the number of the magnetic poles in the magneto generator. Such additional signals must be removed out of the igniting circuit for the semi-conductor switching element.

OBJECT OF THE INVENTION

Accordingly, it is a principal object of this invention to provide a signal source for use in a breakerless ignition system for an internal combustion engine wherein a signal coil or coils can be mounted on a magneto generator without any interference.

It is another object to provide a signal source of the above-mentioned type wherein a required number of signals are obtainable in spite of the number of the magnetic poles in the magneto generator.

A SUMMARY OF THE INVENTION

In accordance with this invention, there is provided a signal source for use in a breakerless ignition system for an internal combustion engine, provided on a flywheel type magneto generator comprising a rotor including a flywheel of magnetic material and a plurality of permanent magnets spaced from each other and mounted on the inner surface of the flywheel and a stator including at least one generating coil for charging a capacitor in the ignition system, and signal source comprising at least one of the permanent magnets of the rotor, magnetically conducting means to conduct flux from a pole piece on the magnet to the periphery of the flywheel and signal coil means disposed outside the flywheel and magnetically coupled between the magnetically conducting means and the flywheel thereacross. The magnetically conducting means may comprise a magnetic member extending through and magnetically insulated from the corresponding magnet and the peripheral wall of the flywheel, with one end of the magnetic member mechanically and magnetically connected to the pole piece on the corresponding magnet and with the other end of the magnetic member exposed to and magnetically insulated from the peripheral wall of the flywheel, so that flux passage is provided from the pole piece of the corresponding magnet to the exposed end of the magnetic member. The signal coil means may comprise a signal coil or coils each having a U-shaped magnetic core around which the coil is wound and mounted on a stator base so that both ends of the core are located in a closely spaced relationship from the periphery of the flywheel. Rotation of the flywheel which is effected by operation of the engine, causes the magnetic core or cores of the signal coil means to bridge the exposed end of the magnetically conducting means and the periphery of the flywheel thereacross for each revolution of the flywheel so that the signal coil or coils have magnetic flux from the magnetically conducting means to the flywheel interlinked therewith to generate an electric signal or signals therefrom in time with rotation of the engine.

The magnetically conducting means may comprise a plurality of magnetic members each extending through one of the selected ones of the permanent magnets in the rotor of the magneto generator. Thus, the signal source can generate any selected number of electric signals therefrom for each revolution of the flywheel type magneto generator.

From the foregoing, it will be understood that the present invention can be designed so that any required number of electric signals are generated from the signal source independently of the number of the poles of the flywheel rotor. Positioning of the signal coil means outside the flywheel allows it to be arbitarily positioned without any restriction. The flywheel of magnetic material prevents the signal coil means from being interlinked with leakage flux except for that from the exposed end of the magnetically conducting means, with the result that no false signal will be generated from the signal coil means.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view of a magneto generator for a breakerless ignition system with a signal source embodying the present invention provided thereon;

FIG. 2 is an enlarged cross sectional view of the signal source section of FIG. 1;

FIGS. 3A and 3B show a curve of magnetic flux interlinked with a signal coil in the signal source of FIGS. 1 and 2 and a curve of signal voltage established by the signal coil;

FIG. 4 is similar to FIG. 2, but illustrating a modification of the signal source according to the present invention;

FIG. 5 is a perspective view of a permanent magnet employed in the signal source of FIG. 4;

FIG. 6 is similar to FIGS. 2 and 4, but illustrating another modification of the signal source according to the present invention; and

FIG. 7 is a fragmentary cross sectional view of a magneto generator with a signal source embodying the present invention wherein an arrangement of the signal source relative to the magneto generator is modified.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is shown a typical embodiment of a flywheel type magneto generator in use for an internal combustion engine with a signal source in accordance with the present invention. The magneto generator is generally indicated by numeral 10 in FIG. 1, and comprises a magnetic rotor 12 including a bowl-like flywheel 14 of magnetic material and a plurality of permanent magnets 16 to 22 which are alternately magnetized in opposite directions and securely mounted on the inside surface of the flywheel 14 in an equally and angularly spaced relationship of one to the adjacent one of the magnets. The permanent magnets are provided with respective magnetic pole pieces 24 to 30 secured to the respective magnets 14 to 22 at the inner face thereof in a conventional manner. Means to secure the magnets and the pole pieces to the flywheel may be rivets and/or adhesive (not shown) which are conventional.

The magneto generator 10 also comprises a stator 32 including two generating coils 34 and 36 wound around respective I-shaped magnetic cores 38 and 40 which are disposed within the flywheel 12 and secured to a stator base (not shown) in a conventional manner, which is in turn securedly mounted on or integral with a crank case also not shown. The generating coils 34 and 36 and therefore, the magnetic cores 38 and 40 are arranged in a spaced relationship to each other by the mechanical angle of 180.degree. and so that poles of the cores 38 and 40 are closely spaced from the pole pieces 24 through 30 of the rotor 12. As well known, these generating coils are adapted to charge a capacitor in a capacitor discharge type breakerless ignition system and to energize lighting load, respectively.

The flywheel 14 of the rotor 12 may comprise a hub (not shown) on which an engine shaft or a crank shaft is mounted by any suitable means, such as a nut and extends through a hole 14a in the flywheel 14. Thus, the magneto generator rotates in time with rotation of the engine.

A signal source of this invention is generally indicated by numeral 42 and comprises one of the magnets designated at 16. The signal source also comprises magnetic flux conducting means or magnetically conducting means with one of the ends communicating with the pole piece 24 on the magnet 16 and with the other end exposed at the outer periphery of the flywheel 14. In the illustrated embodiment, the magnetic flux conducing means comprises a rod-like magnetic material in the form of a flush bolt 44 loosely extending through a hole 16a in the magnet 16 and threaded into the corresponding pole piece 24 so that the flush bolt 44 is mechanically and magnetically bonded with the pole piece 24. The magnetic flush bolt 44 has the head countersunk in a tapered opening 14b in the flywheel 14 in a spaced manner from the wall defined by the opening and the space between the head of the bolt 44 and the opening wall is filled with non-magnetic material 46 in a magnetically insulating relationship from the flywheel 16 so that the bolt 44 is secured at the head thereof to the flywheel 16. Thus, it will be noted that the magnetic flux conducting means of the illustrated embodiment serves to secure the magnet 16 and the pole piece 24 to the flywheel 14.

The signal source 42 also comprises a signal coil 48 disposed outside and adjacent to the flywheel 14 and wound around a U-shaped magnetic core 50 with two legs 50a and 50b closely spaced from the periphery of the flywheel 14. The signal coil 48 may be mounted by securing the core 50 to the stator base or a flywheel cover not shown by means of setscrews 52 extending through the core and threaded into the base or cover.

While the flywheel 14 is being driven by the engine, the core legs 50a or 50b of the signal source 42 faces the head of the flush bolt or conducting means for each revolution of the flywheel to complete a magnetic circuit from the magnetically conducting means through the core 50 to the flywheel 14. Thus, as shown in FIG. 2, when the core 50 at one of the legs 50a and 50b thereof faces the magnetically conducting means 44, magnetic flux .phi. flows from the N pole of the magnet 16 through the conducting means 44 to the core 50 and then through the flywheel 14 to the S pole of the magnet 16. As a result, the flux is interlinked with the signal coil 48 to produce an electric signal V therefrom (see FIGS. 3A and 3B). As seen from FIG. 3A, the flux .phi. through the core 50 has generally a sine wave form and therefore, the signal coil 48 has the voltage V of a substantial sine wave form induced therefrom. The voltage V, which is generated in time with rotation of the engine, is available as a control signal by rectifying one half wave of the voltage V. Since the flywheel 14 is made from magnetic material, flux will not leak out of the flywheel except for the through hole 16a therein and therefore, false signals will not be generated from the signal coil 48.

FIG. 4 shows modification of the signal source 42 wherein the permanent magnet 16 and the corresponding pole piece 24 are secured to the flywheel by means of the magnetic bolt 44 serving as magnetically conducting means and also by means of another non-magnetic bolt 54. As seen from FIG. 5, the magnet 16 may be provided at both ends thereof with grooves 56 and 56' extending circumferentially of the arcuate magnet 16 and opening at the edges thereof. The magnetic bolt 44 extends through the groove 56 with the head of the bolt spaced by the non-magnetic material 46 from the flywheel in the same manner as shown in FIGS. 1 and 2 and the non-magnetic bolt 54 extends through the groove 56' with the head of the bolt countersunk in a tapered hole 58 in the flywheel.

FIG. 6 shows further modification of the signal source 42 wherein magnetically conducting means comprises a stud 44' welded onto the magnetic pole piece 24 at the back thereof. The magnetic stud 44' has the top end threaded into a non-magnetic and tapered nut 60 which in turn engages a tapered hole 14b' in the flywheel 14. It will be understood that if the magnet 16 and the pole piece 24 are secured to the flywheel 14 by alternative means in a conventional manner, then the non-magnetic nut 60 will be omitted.

Referring now to FIG. 7, there is illustrated a modification of a signal source arrangement in which the signal coil means 48 of the signal source 42 is angularly disposed between two of the stator cores 38 and 40 which are arranged in an angularly spaced relationship of approximate 120.degree. to each other. The feature of FIG. 7 has an advantage in that flux from the signaling magnet 16 is interlinked with the signal coil means at higher density than in the foregoing embodiment. More particularly, with the feature of FIG. 7, when the signaling magnet moves far away from the stator cores 38 and 40, it moves toward the signaling core 50 so that the flux therefrom pass through the signaling core, resulting in that flux of high density from the signaling magnet 16 is more effectively interlinked with the signal coil means. It will be noted that the signaling core 50 may be preferably disposed intermediate of the stator cores 38 and 40, but that it may be disposed in a slightly more closely spaced relationship from either of the stator cores 38 and 40. Assuming that the flywheel 14 rotates in a direction as indicated by an arrow in FIG. 7, as the signaling magnet 16 moves toward the stator core 40 the flux from the magnet is restrained from flowing through the stator core 40 because of magnetic counteraction or armature reaction on the corresponding generating coil 36. Therefore, the signaling core 50 may be preferably disposed closely spaced from the leading stator core 40 as shown in FIG. 7. If desired, that pole portion of the stator core 40 adjacent to the signaling core 50 may be preferably cut off as indicated at dotted line of FIG. 7.

While some preferred embodiments of the present invention are described, it will be appreciated by those skilled in the art that various changes and modifications in construction and arrangement might be made without departing from the spirit and scope of the invention, which has been defined only in the appended claims.

Claims

What is claimed is:

1. In a combination of a flywheel magneto generator for a breakerless ignition system for use in an internal combustion engine, said generator comprising a rotor including a bowl-like flywheel of magnetic material, a plurality of permanent magnets spaced from each other and mounted on the inner surface of said flywheel and respective pole pieces mounted on said magnets at the inner faces thereof, and a stator including generating coil means disposed inside said rotor and closely spaced from said pole pieces of said rotor, a signal source comprising at least one of said permanent magnets on said flywheel, magnetically conducting means having one end directly connected to said pole piece on said one permanent magnet and the other end exposed at the outer periphery of said flywheel and magnetically insulated therefrom, and signal coil means disposed outside said flywheel and in a closely spaced relationship with said outer periphery of said flywheel and said exposed end of said magnetically conducting means.

2. The invention as set forth in claim 1, wherein said magnetically conducting means comprises a magnetic member extending through said one permanent magnet in a magnetically insulated relationship therefrom.

3. The invention as set forth in claim 2, wherein said magnetic member is in the form of a bolt with both ends mechanically connected to said pole piece on said one magnet and said flywheel.

4. The invention as set forth in claim 2, wherein said magnetic member is in the form of a stud with one end welded to said pole piece on said one magnet and with the other end connected by a magnetically insulating nut to said flywheel.

5. The invention as set forth in claim 1, wherein said signal coil means is angularly offset from said generating coil means.

6. The invention as set forth in claim 1, said generating coil means comprising a plurality of coils and wherein said signal coil means is positioned angularly adjacent to one of said generating coils.

7. In a combination of a flywheel magneto generator for a breakerless ignition system for use in an internal combustion engine, said generator comprising a rotor including a bowl-like flywheel of magnetic material, a plurality of permanent magnets spaced from each other and mounted on the inner surface of said flywheel and respective pole pieces mounted on said magnets at the inner faces thereof, and a stator including generating coil means disposed inside said rotor and closely spaced from said pole pieces of said rotor, a signal source comprising at least one of said permanent magnets on said flywheel, magnetically conducting means having one end magnetically connected to said pole piece of said one permanent magnet and an opposed end, said flywheel defining an opening for passage of said magnetically conducting means therethrough whereby said opposed end of said magnetically conducting means is exposed at the outer periphery of said flywheel, magnetically insulating means seated in said flywheel opening for magnetically insulating said magnetically conducting means from said flywheel in its said passage through said flywheel, and signal coil means disposed outside said flywheel and in a closely spaced relationship with said outer periphery of said flywheel and said opposed end of said magnetically conducting means.