GB1395954A - Servomechanism - Google Patents

Abstract

1395954 Power-assisted steering GEMMER FRANCE 26 July 1972 [28 July 1971 17 March 1972 19 July 1972] 35001/72 Heading B7H [Also in Division G1] A follow-up switch incorporated in the steering column of a vehicle to allow an electric motor to assist the steering includes a torsion member measuring the applied torque and having an adjustable elasticity to preset the torque at which the servo motor is energized. As shown (Figs. 1, 2), the steering column comprises a first section 1 attached to the steering wheel 4 and a second section 2 attached to the steering members, coupled by a torsion bar 3. Each section 1, 2 carries one part 5, 6 respectively of a follow-up switch. When the torque applied to the steering wheel 4 exceeds a preset value the angular displacement between sections 1, 2 allows the wings of part 5 to contact the sides of the slots in part 6, thereby switching on a servomotor 18. The torque may be measured by a circular resistance potentiometer 8 fixed to part 6 with its slides driven through gears 12, 13 by section 1 of the steering column, to produce a torque signal which is fed to motor 18, with the follow-up switch 5, 6 determining the direction of rotation. The torque signal may be modified by a speed signal derived from a potentiometer 20 (Fig. 5) whose slider is coupled to the pointer of a speedometer 19, and is wound in three sections A, B, C giving different relationships for high, normal and low speeds. At high speeds the signal may be of opposite polarity to reduce the power assistance supplied by motor 18. The motor may be coupled to the steering mechanism through an electromagnetic clutch which is energized in parallel with the motor. The torsion bar 3 may be replaced by alternative spring arrangements whose elasticity is adjustable.