Patent GB-908916-A (GB)
Title: Improvements in or relating to control arrangements of electric starter motors for internal combustion engines
IPC: H01H5/02
Filed: 1960-10-17
Abstract: 908,916. Electric switches. BOSCH G.m.b.H., ROBERT. Oct. 17, 1960 [Nov. 14, 1959], No. 35436/60. Class 38 (5). [Also in Group XXXV] A switch for preventing untimely actuation of an electric starter motor of an internalcombustion engine is controlled by a force dependent on a prevailing operating condition of the engine, such as the inlet manifold vacuum, and by an opposing magnetic force provided by a permanent or electromagnet. In Fig. 1, housing 14, kept at atmospheric pressure by holes in its wall, is closed by a diaphragm 15 subjected to the inlet manifold pressure through the pipe socket 18. Soft iron armature 21, connected to diaphragm 15 by stud 25, projects into an annular axially magnetized permanent magnet 20 and carries a switch member 22 which bridges contacts 23, 24 in series with a starter motor switch 13 and a tapping 26 of an operating coil controlling starter motor contactor 11, when the engine is stationary and hence no manifold vacuum exists. When switch 13 is closed, current from the battery 12 flows to tapping 26 and energizes coil sections 29, 27 in parallel, producing mutually assisting magnetic fields which immediately close contactor 11 to energize the starter motor 10. Inlet manifold vacuum increases with engine speed and exerts a force on the diaphragm 15 acting in the direction of the arrow, which will eventually overcome the counter holding force of the magnet 20. The opening of contacts 23, 24, caused by the movement of the member 22 is accompanied by armature 21 releasing from magnet 20, thus reducing their mutual attraction and ensuring that a relatively low vacuum will maintain the contacts open. Opposing magnetic fields now produced by current flowing serially through the now magnetically opposing coil sections 27, 29 causing contactor 11 to deenergize the motor 10. Transient drops in manifold vacuum may be prevented from causing the bridging of contacts 23, 24 by the inclusion of a throttle valve between the diaphragm 15 and the inlet manifold. In Fig. 4, when the switch 13 is closed, current flows through contactor 43, 44, bridged by a member 40, to a starter motor contactor draw-in coil 52 in series with the stator motor 10 and also through contactor 46, 47, bridged by a member 41 through contactor holding coil 53, thus closing contactor 11 and energizing the starter motor. Manifold vacuum exerted by the engine starting but running below idling speed, acts on diaphragm 15 which lifts member 40 against the opposing force of the magnet 20 acting through a soft iron armature 48 on a soft iron ring 45 attached to member 40, thus breaking the draw-in coil current. Member 40 lifting, reduces the mutual attraction between the magnet 20 and ring 45 and enables a low vacuum to maintain this position. At increased engine speed and manifold vacuum, diaphragm 15 is moved further so that flange 51 of stud extension 50 attached to it and passing through longitudinal bore 49 abuts the armature 48 and so breaks the circuit to the holding coil 53 by lifting the switch member 41 off contacts 46, 47 against the counter force of the magnet 20 and thus releasing contactor 11. Pull-in coil 52 and holding coil 53 may be omitted and a similar actuating coil as in Fig. 1 substituted, the reduced holding current for it being thus provided through the contacts 46, 47 bridged by member 41 in series with an additional resistor. The system of Fig. 1 may be built integrally with an ignition timing device, when diaphragm 15 may be arranged to carry out both functions.