GB926523A - Spark ignition apparatus for internal combustion engines - Google Patents

Abstract

926,523. Ignition magnetos. JOSEPH LUCAS (INDUSTRIES) Ltd. July 24, 1961 [Aug. 16, 1960 ; Dec. 6, 1960], Nos. 28323/60 and 41898/60. Class 35. [Also in Group XXVII] The generator illustrated in Figs. 1 to 4, is suitable for use with a four-cylinder engine, and includes a stator 11 (Figs. 3 and 4), incorporating two permanent magnets 12 and three polepieces 13, 14, 15, separated by a resin moulding 16. Embedded within the moulding 16 are a pair of pickup coils 17, 18 which surround the poles 13, 15 respectively. The stator 11 is fixed to the body of the engine, whilst the rotor 19 is fixed to the engine crank-shaft for rotation therewith. The rotor 19 is of generally annular form, but at diametrically opposite positions has secured thereto a pair of magnetic plates 20 which rotate between the extremities of the poles 13, 14, as shown in Fig. 4. The plates 20 when considered in the direction of rotation of the rotor 19 vary from a minimum radial width to a maximum radial width at the points 21. It will be appreciated that the shape of the pulses generated in the coil 17 will depend on the speed of rotation of the rotor and on the radial thickness of the portion of a plate 20 between the poles 13, 14. Thus, during each half-revolution of the crank-shaft the voltage of the pulse developed in the coil 17 will vary between limits determined by the speed of rotation and the shape of the plates 20, the plates 20 being shaped so that the pulses have a sloping or curved leading edge the steepness of which increases with increasing engine speed. The generator produces a secondary output in the coil 18 by virtue of a pair of studs 22 passing between the poles 14, 15. The studs are conveniently of square cross-section, but may be of any other cross-section such that the leading edge of each stud cuts the lines of force at right angles when passing between the poles 14, 15. The positioning of the studs 22 is such that a relatively large voltage will be developed in the coil 18 immediately before the maximum voltage is developed in the coil 17. In Figs. 6 and 7 the rotor 57 is formed from magnetic material, whilst the stator comprises a pair of plates 58, 59 of magnetic material interconnected by a magnet 60. The plates 58, 59 are slotted to provide a series of unequal limbs 61 on some or all of which unequal windings 62 are wound in series. In a further modification (not shown), the limbs 61 may project axially out of the plane of the plate 59. In this case the limbs 61 are the same length, but again carry unequal windings. In a further modification, the rotor may be driven by the engine through gearing Ignition systems are described (see Group XXVII).