GB1335136A - Electric induction generator systems for internal combustion engines having electronic ignition systems - Google Patents

Abstract

1335136 Generators for ignition systems ROBERT BOSCH GmbH 6 July 1971 [28 July 1970] 31591/71 Heading H2A A generator system for use with a motor cycle internal combustion engine having electronic ignition comprises a set of magnets M<SP>1</SP> mounted inside a cylindrical rotatable magnetic body 30 so that as they rotate they move past ends of (a) a magnetic core 29 carrying an A.C. winding 15 for charging a storage capacitor 11, and (b) two axially-spaced but radially-aligned limbs 38, 39 of a further core structure carrying a control winding for triggering an ignition firing thyristor 20, this winding comprising two portions 25<SP>1</SP>, 25<SP>11</SP>, one on each limb, and the voltages induced in these portions being arranged to cancel each other out except at that point in each revolution of the set of magnets M<SP>1</SP> at which an ignition firing pulse is required. Generation of the firing pulse is achieved by introducing an asymmetry into the magnetic structure at the required point in any of the following ways: (i) The upper part 40 of the polepiece of one pole M1<SP>1</SP> and the lower part 41 of the polepiece of an adjacent pole M2<SP>1</SP> may project into the interpolar gap Z so that at this angular position of the rotor 30 flux passes from one projection to the other via the two limbs 38, 39 and either an interconnecting yoke 46 or a magnetic hub 31 of the rotor. The yoke, if provided, may be T or H shaped (Figs. 13, 14, not shown). (ii) A magnetic projection (S1, Fig. 3, not shown) may be provided on the magnetic rotor hub 31 so that it momentarily introduces a flux path via one limb of lower reluctance than the flux path via the other limb and thus unbalances the voltages induced in the respective winding portions 25<SP>1</SP>, 25<SP>11</SP>. The radially-outer ends of the two limbs may be interconnected by a magnetic yoke (46). (iii) As an alternative to (ii), a recess cut in the hub will likewise momentarily unbalance the voltages (Fig. 7, not shown). (iv) As an alternative to (iii), the recess may be cut in one of the magnets M<SP>1</SP> (Fig. 10, not shown). In the case of (ii), (iii) and (iv), the projection/ recess may be tapered to increase the range of timing adjustment. Alternatively, a small projection/recess may precede a larger one, the small one being of such a size that it only causes a pulse of sufficient magnitude to fire the thyristor 20 to be generated when the rotor is rotating above a certain speed, so that when this speed is reached the ignition timing is suddenly advanced. In the case of (i) when no magnetic yoke 46 is being used, to prevent control pulses being generated if the rotor rotates in the wrong direction diodes are connected across or in series with the winding portions 25<SP>1</SP>, 2511, or auxiliary windings are provided, to suppress or cancel such undesired pulses (Figs. 16-18, not shown).