GB2181099A

GB2181099A - Power assisted steering gear

Info

Publication number: GB2181099A
Application number: GB08319425A
Authority: GB
Inventors: Ian Geoffrey Kirby
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1983-07-19
Filing date: 1983-07-19
Publication date: 1987-04-15
Also published as: GB2181099B; US4560023A; JPS6038265A; GB8319425D0; DE3425648A1

Description

1

GB2 181 099A 1

SPECIFICATION

Power assisted steering gear

5 This invention relates to a power assisted steering gear.

On front wheel drive vehicles, the steering gear is mounted at the back of the engine compartment on the rear bulkhead. Space is 10 limited in this region, and there are therefore packaging problems associated with the use of conventional power assisted steering gears which have a valve for controlling hydraulic fluid flow aranged between the steering gear 15 rack and the steering wheel. It is undesirable to locate the valve within the passenger compartment, and a conventional gear therefore projects a long way into the engine compartment.

20 British Patent No. 1,234,032 describes a steering gear where the rack and pinion of the gear is arranged between the valve and the steering wheel shaft. This results in a compact arrangement. However, it is considered 25 necessary to provide torsional resistance to turning of the steering wheel to give steering "feel". In this British Patent, tubular springs are provided in a special housing between the rack and pinion and the steering wheel. This 30 arrangement has not proved satisfactory, for production purposes since the characteristics of the springs used are not sufficiently uniform.

According to the present invention, there is 35 provided a power assisted steering gear having a pinion meshing with a steering rack, an input shaft and a control valve for controlling the flow of hydraulic fluid which, in use,

moves the rack, the pinion and rack being 40 positioned between the input shaft and the valve, the pinion being hollow and accommodating a torsion bar, the steering gear further comprising an input shaft extension which connects the input shaft to the valve, one end 45 of the torsion bar being rotationally fast with the input shaft and the other end being rotationally fast with the pinion.

The invention will now be further described, by way of example, with reference to the ac-50 companying drawing which is a cross section through a power assisted steering gear in accordance with the invention.

The gear has an input shaft 10 which, in use, will be connected to a steering wheel. A 55 rack 12 (shown only in transverse cross section) is connected to steerable road wheels in a conventional manner, and is provided with a hydraulic actuator arrangement (not shown) which can move the rack in one longitudinal 60 direction or the other. The actuator arrangement is controlled by a valve 14 which is also of conventional form, and has a rotor 16 and a sleeve 18. A pinion 20 extends between the input shaft 10 and the valve 14. 65 An input shaft extension rod 22 is held fast to the shaft 10 by a pin 24. Th other end of the rod extends through a bore in the pinion 20, and engages, through splines 25, with the valve rotor 16.

70 A tubular torsion bar 26 surrounds the rod 22. At one end 28, this bar is fixed to the input shaft 10, and at the other end it is fixed to the pinion 20 by a pin 30. The sleeve 18 of the valve 14 is also fixed to the pinion by 75 a pin 32.

When the input shaft 10 is turned by the steering wheel, the valve rotor 16 is also turned, through the rod 22. At the same time, the right hand end of the torsion bar 26 is 80 turned. The pinion 20 is however initially held stationary by the rack and there is therefore a relative movement, as the torsion bar 26 twists, between the rotor 16 and the sleeve 18. This allows a flow of hydraulic fluid 85 through the valve which will be directed to the hydraulic actuator arrangement to produce movement of the rack 12 in one direction or the other, and thus a movement of the steer-able road wheels. The valve operation will be 90 conventional. Bearings 34 provide resistance to the axial thrust of the pinion 20. Safety dogs 36 allow steering control to be maintained manually in the event of a fluid failure in the power supply.

95 The positioning of the valve 14 on the opposite side of the rack and pinion 12, 20 from the input shaft 10 makes it possible to reduce the distance between the driving position and the location of the steering rack. The 100 input shaft need be no longer than for a manual steering gear. Intrusion of the valve into the drivers foot area is avoided. Attachment of the pressure and return hoses to the gear is facilitated. Also, since the valve is remote 105 from the input shaft, there is no need to provide a shield to prevent hot oil entering the passenger compartment in the event of a hose failure. Steering "feel" is provided by the tubular torsion bar 26.

110

Claims

1. A power assisted steering gear having a pinion meshing with a steering rack, an input shaft and a control valve for controlling the 115 flow of hydraulic fluid which, in use, moves the rack, the pinion and rack being positioned between the input shaft and the valve, the pinion being hollow and accommodating a torsion bar, the steering gear further comprising 120 an input shaft extension which connects the input shaft to the valve, one end of the torsion bar being rotationally fast with the input shaft and the other end being rotationally fast with the pinion.

125

2. A steering gear as claimed in Claim 1, wherein the torsion bar is tubular, and the input shaft extension passes through the bar.

3. A power assisted steering gear substantially as herein described with reference to the 130 accompanying drawing.

2

GB2 181 099A 2

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.