GB1204385A - Improvements in or relating to motor vehicle steering devices - Google Patents

Abstract

1,204,385. Hydrostatic steering devices. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. 10 Nov., 1967, No. 51325/67. Heading B7H. [Also in Division F2] A manually operated or power assisted steering device for motor vehicles, comprises a fluid pump 4 driven by rotation of the steering shaft 2 and connected via a valve member 60 to a servomotor 9 acting on the steered wheels of the vehicle, the rotation of the steering shaft 2 being geared up by an internally-toothed ring gear 10 fast therewith and meshing with an externally-toothed pinion 11, which is rotatably mounted eccentrically on the shaft 14, 15 driving the pump 4, but which is substantially prevented from rotating about its own axis and is constrained to a circular orbit about the axis of the ring gear 10. In one embodiment, the pinion 11 has lugs 28 engaging grooves 21 and 22 formed in the ring 20, the grooves 21 and 22 engaging the bushed pins 23 and 24 of a cardan bolt 25 which is universally mounted (but capable of only limited rotation) by pins 30, 31 engaging slots 32, 33 in a housing 34. A highpressure fluid power-assistance pump 6 is continuously driven by the vehicle and normally its output is directed back to the reservoir 7 by a control device 8 which comprises a rotary valve member 60 secured to the cardan bolt 25 and a fixed valve sleeve 61, comprising longitudinal control grooves 96-99a and b, 92-95a and b co-operating with each other and with annular grooves 75-79 in the housing 16. When the steered wheels offer resistance to movement greater than a certain value, then the cardan, bolt 25 rotates a limited amount against springs 66, 67 and high pressure fluid is then delivered by the control device 8 via channels 50<SP>1</SP> and 51<SP>1</SP>, or 52<SP>1</SP> and 53<SP>1</SP> to the suction chambers of the twin-flow gear pump 4 and thence via channels 52<SP>1</SP> and 53<SP>1</SP>, or 50<SP>1</SP> and 51<SP>1</SP> back to the control device 8 and thence to chamber 87 or 88 of the servomotor 9, the chamber 88 or 87 discharging fluid via the control device 8 to the reservoir 7. The rotary valve member 60 may be constructed so that a shock at the servomotor 9 is or is not transmitted by the fluid to the pump 4 to produce a movement of the member 60, so that the power assistance may or may not counteract the shook. In another embodiment, the cardan bolt 25 is dispensed with, and the pinion 11 is connected to an adjacent disc capable of a limited rotary movement (against spring action) which rotates an axially displaceable control valve member. Rotation of the control valve member causes axial displacement thereof by means of coarse screw-threads on the member and the fixed housing 16, the control valve member having circumferential control grooves co-operating with the circumferential grooves in the housing 16. The disc is centred by a lever acted oppositely on by two springs.