GB818595A - Improvements in or relating to coupling means for starter-motors - Google Patents

Abstract

818,595. Engine starter drives. SIMMS MOTOR UNITS Ltd. Aug. 13, 1957 [May 14, 1956], No. 14988/56. Class 7(5) A starter drive comprises a solenoid having a magnetic circuit including a magnetic member which on energization of the solenoid is thereby urged to cause the starter pinion to move to a position for at least initial or partial meshing with the engine gear wheel and means including at least one other magnetic member for automatically modifying the magnetic circuit so that when the pinion is fully in mesh with the gear wheel the other magnetic member is urged by the solenoid to retain the pinion in mesh with the gear wheel. Current is supplied to the coil 34 thereby setting up a magnetic field causing the sleeves 36, 37 to move to the left to a position of minimum reluctance carrying with them the shift collar 22. Electric power is then applied to the starter motor. The thrust transmitted by the spring 23 urges the pinion 15 towards the ring gear 24 of the engine flywheel and as soon as the relative positions of the teeth of the pinion and ring gear permit the pinion will move partially into mesh. Rotation of the starter motor acting through the helical spline 12 on the shaft 11 jacks the pinion forward into complete mesh with the ring gear 24. As the pinion moves into mesh it carries with it the sleeve 37 which opens an air gap between the extremities of the legs 39 and the end cap of yoke 35 by moving away therefrom the plain iron sleeve 44. With further movement of the sleeve 37 the magnetic splines 46 protrude from the slots between the legs 39 so presenting a path of low reluctance to the magnetic flux. This causes a force to be developed which holds the pinion in mesh with the engine. When the engine starts the freewheel 17 permits over-running of the pinion relative to the shaft 11. The full power of the starter motor may be applied to the shaft when the flange 38 first makes contact with the yoke 35 or the application of full power may be delayed until the pinion is fully in mesh with the gear ring. This may be brought about automatically. The sleeve 44 and the ring 43 carrying the splines 46 are attached to a non-magnetic coupling piece 45 by silver soldering. In Fig. 6 two shift collars 51, 52 are slidably mounted on the sleeve 19. The shift collar 51 operates through a yielding compliance spring 53 to move the pinion 15 to the left. Spring 53 is preloaded against the pinion return spring 27. A second compliance spring 56 acts between the shift collar 52 and a retaining ring 57. An outer sleeve 62 has secured to it internally a plain ring 67 of non-magnetic material which ring 67 abuts against the end of the inner sleeve 63. The outer sleeve 62 carries two contact carrying pillars 71 which carry a flat annular copper contact 69 which is insulated from the pillars 71 by an insulating ring 72 mounted on a steel plate 73 which slides on to the pillars 71. Contact pressure springs are interposed between the plate 73 and retaining rings 75 on the pillars 71. The contact 69 co-operates with a contact 76 connected to a terminal 77 and a contact 78 connected to one end of the field winding 79 of the starter motor 81. The starter motor is thus energized only when the contact 69 bridges the contacts 76 and 78. When the starter switch is closed current is supplied to the coil 34 thereby causing the sleeve 62, 63 to move to the left thereby imparting thrust to the compliance spring 53. The contact 69 is also moved into contact with the contacts 76, 78 and closes the circuit of the motor 81. The compliance spring 53 urges the pinion towards the gear 24 for partial meshing. When the pinion is fully in mesh it carries with it the sleeve 63 which exerts a force holding the pinion in mesh. The free wheel 17 may be omitted and the armature of the starter motor may be strengthed as described in the Specification to withstand the speeds to which it may then be subjected.