GB263287A - Improvements in or relating to ignition magnetos for internal combustion engines - Google Patents

Abstract

263,287. British Lighting & Ignition Co., Ltd., and Hutton, J. C. Dec. 8, 1925. Magneto-electric machines.-To obtain four or more sparks per revolution in a rotating-magnet fixed-armature magneto, such as described in Specifications 184,905, and 185,192, a set of two or more pole-pieces is fixed at each end of the armature core, the pieces at one end being displaced with regard to those at the other end in the axial direction of the machine. Fig. 1 shows a machine with a bipolar magnet giving four sparks per revolution and Fig. 2 shows an end view of the armature and pole-pieces. The limbs b, c of the armature respectively have pairs of pole-pieces d, e and h, g 180 degrees apart and are bent in opposite directions at the two ends of the armature so that the poles are separated axially by a distance k. The poles g, e are separated by gap circumferentially without overlapping, whereas the poles d, h overlap. In the position shown, flux passes from the magnet pole N through the pole d, limb b, core a, limb c, as shown in dotted lines, to the pole and magnet pole S. As the magnet rotates and its poles come successively opposite the armature poles in the order h, e; e, g; g, d the flux through the core a is successively reversed, thus giving four spares during the revolution. The overlapping poles may alternatively be on the underside of the rotor instead of above it as shown. Also, a fourpole rotary magnet may be employed, with poles of alternate sign, in which case the flux breaks occur at each of the four armature pole-pieces. Fig. 7 shows a form for giving six sparks per revolution of a bipolar magnet having six polar surfaces N, S. The axially displaced pairs of armature poles d, e, g, h are spaced at 120 degrees. In an alternative six-spark form, each end of the armature core has three poles symmetrically spaced at 120 degrees and co-operating with a magnet having two, four or six poles spaced apart by 60 degrees. Other numbers of sparks per revolution may be obtained by increasing the number of poles on the rotor or armature core or both and modifying their angular spacing. for examples, 45 degrees for eight sparks or 36 degrees for ten sparks. Specification 263,286 also is referred to.