GB2145383A

GB2145383A - Control valve for use in a power-assisted steering mechanism

Info

Publication number: GB2145383A
Application number: GB08419258A
Authority: GB
Inventors: Benjamin Ward
Original assignee: SUPRA STEERING Ltd
Current assignee: SUPRA STEERING Ltd
Priority date: 1983-08-20
Filing date: 1984-07-27
Publication date: 1985-03-27
Also published as: GB8419258D0; GB8322479D0; GB2145383B

Abstract

A control valve for use in a power-assisted steering mechanism comprises relatively rotatable inner core 11 and outer sleeve 12. The core 11 is formed on its exterior surface with a plurality of longitudinally extending control lands 24 which serve to control flow of hydraulic fluid through slots 21 formed in the sleeve 12. Each of said slots 21 extends in a longitudinal direction through the wall of the sleeve and each of the two oppositely disposed and circumferentially spaced surfaces of each slot 21 is formed with a channel-shaped recess 23. The recesses 23 provide a progressive increase in power assistance. The construction of the control valve facilitates economical manufacture by milling, broaching and hobbing operations. <IMAGE>

Description

SPECIFICATION Control valve for use in a power-assisted steering mechanism This invention relates to a control valve for use in a power-assisted steering mechanism, the valve being of the kind which incorporates a pair of relatively rotatable co-axially arranged members, namely an inner core and an outer sleeve which surrounds the core, the valve being arranged in use to control the flow of a pressurised fluid which in use is commonly supplied by a pump driven by the engine of the vehicle in which the associated steering mechanism is fitted. The object of the present invention is to provide such a control valve in an improved form which is economical to manufacture yet efficient in operation.

In accordance with the invention, there is provided a control valve for use with a power-assisted steering mechanism, said valve comprising a pair of relatively rotatable co-axially arranged members, namely an inner core member and an outer sleeve member which surrounds the core member said sleeve member being formed with a plurality of longitudinally extending slots which each extend through the wall of the sleeve member and the core member being formed on its exterior surface with a plurality of longitudinally extending control lands which correspond in number to the number of said slots in the sleeve member, wherein each of the two oppositely disposed and circumferentially spaced surfaces of each of said slots is formed with a recess which opens into the interior of the slot.

The invention will now be more particularly described with reference to the accompanying drawings wherein Figure l is a longitudinal sectional view of one example of a control valve in accordance with the invention, Figure 2 is a sectional end view, on an enlarged scale, of part of said control valve, and Figure 3 is a scrap longitudinal sectional view, also on an enlarged scale, of the sleeve part of the valve.

Referring firstly to Figure 1 the control valve shown therein comprises a housing 10 in which is mounted a control valve which comprises an inner or core member 11 and a co-axially arranged outer sleeve member 12, the core member projecting into the interior of the sleeve member 12. Said members 11 and 12 are relatively rotatable and the core member 11 projects at one end 13 from the housing 10 and is there provided with a plurality of external splines by means of which it can be connected to a drive-rotatable shaft which, at its upper end, would be connected to the steering wheel of a vehicle in which the associated steering mechanism is fitted.

The aforesaid inner and outer members 11 and 12 are interconnected by a torsion bar 14 which is pinned at one end 15 to the outer or sleeve member 12 and is similarly pinned at the other end 16 to the core member 11. Furthermore the exterior of one end of said sleeve member 12 is formed with teeth 17 to form a pinion which engage with the teeth 18 of a rack 19 which extends through the housing 10, the opposite ends of said rack being connected to the steering mechanism of the vehicle, with the rack being adapted to support a piston which is slidable in an enclosing cylinder (not shown). The aforesaid control valve is arranged, on turning of the aforesaid core member 11 by rotation of the vehicle steering wheel, to control the flow of pressurised fluid (supplied by an engine driven pump) to and from said piston and cylinder unit.Details of the hydraulic connections between the control valve and the piston and cylinder unit may be of any known or conventional form and do not form any part of the present invention. Suffice it to say however the sleeve member 12 is surrounded, in the housing 10, by a further sleeve 20 which would be provided with suitable ports providing an inlet or inlets to the interior of the control valve and an outlet or outlets to the piston and cylinder unit.

Referring now to Figures 2 and 3, it will be seen that the sleeve member 12 is formed with a plurality (conveniently four) slots 21 which extend through the wall of the sleeve, each of said slots extending in a generally longitudinal or axial direction and being closed at each of its ends. The slots are conveniently formed by means of a milling operation but in order to avoid unneccessarily sharp edges at positions where the slots break through the inner wall of the sleeve member 12, the two ends of each slot are each formed adjacent to said inner wall with a generally radially extending surface indicated by reference numeral 22 in Figure 3.Furthermore, as shown in Figure 3 each of the two oppositely disposed, circumferentially spaced, surfaces of each slot 21 is formed (conveniently by means of a broaching operation) with an open-ended channeshaped recess 23 which opens into the interior of the slot.

As will be seen in Figure 2 the inner core member 11 is of generally cylindrical configuration but it is formed on its exterior surface with a plurality of longitudinally extending lands 24 which correspond in number with the number of said slots 21. Thus in the example now described four lands 24 are provided and as shown in Figure 2 the width of each land 24 is slightly less than the width of each slot 21.

A core member 11 formed as above described can conveniently be manufactured by means of a hobbing operation.

It will be appreciated that when the core member 11 is turned relative to the sleeve member 12 in either direction of rotation from the neutral position seen in Figures 2 then the spaces indicated in Figure 2 by reference numerals 25, 2627 and 28 will each be cut off from one of the aforesaid slots 21 whilst being brought progressively into a fuller communication with another slot 21. The aforesaid channel-shaped recesses 23 in the slots 21 will provide for a more gradual cut off as the core member 11 is being turned which will provide for a progressive and gradual increase in the hydraulic assistance offered by the control valve.

The above-mentioned arrangement in which said recesses 23 are formed in the slots 21, emabling said slots to be formed by means of milling and broaching operations whereas the core member 11 can be formed buy a hobbing operation represents a considerable saving in machining time as compared with hitherto known constructions of control valves used in steering mechanisms. The present invention does therefore provide a very economical form of manufacture.

In the above-described embodiment, the sleeve member 12 extends at its right hand end (as seen in Figure 1) to form a pinion having pinion teeth 17 and consequently the sleeve member and the pinion are of an integral construction. In an alternative construction however (not shown), the sleeve member 12 is formed separately from the pinion and the latter is formed integrally with said further sleeve 20.

In this case the separately formed sleeve 12 is inserted into sleeve 20 with interference fit so that sleeve 20 (and pinion and sleeve 12 all rotate together.

It is also to be understood that the invention can be applied to steering mechanisms of kinds other than the rack and pinion kind referred to above.

Claims

1. A control valve for use with a power-assisted steering mechanism, said valve comprising a pair of relatively rotatable co-axially arranged members, namely an inner core member and an outer sleeve member which surrounds the core member, said sleeve member being formed with a plurality of longitudinally extending slots which each extend through the wall of the sleeve member and the core member being formed on its exterior surface with a plurality of longitudinally extending control lands which correspond in numbertothe numberofsaid slots in the sleeve member, wherein each of the two oppositely disposed and circumferentially spaced surfaces of each of said slots is formed with a recess which opens into the interior of the slot.

2. A control valve as claimed in Claim 1 in combination with a rack and pinion vehicle steering gearwherein said outer sleeve is formed integrally with said pinion of the steering gear.

3. A control valve as claimed in Claim 1 in combination with a rack and pinion vehicle steering gear wherein said outer sleeve is formed separately from said pinion of the steering gear.

4. A control valve as claimed in any one of the preceding claims wherein each of said recesses formed in the slot surfaces of the sleeve member is of open-ended channel-shaped configuration.

5. A control valve as claimed Claim 4 wherein each of said recesses is formed by means of a broaching operation.

6. A control valve for use with a power-assisted steering mechanism, said control valve being substantially as hereinbefore described with reference to and as shown in the accompanying drawings.