GB2032361A

GB2032361A - Steering valve arrangement for vehicles

Info

Publication number: GB2032361A
Application number: GB7930859A
Authority: GB
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1978-09-06
Filing date: 1979-09-05
Publication date: 1980-05-08
Also published as: DE2838789A1; IT1162390B; IT7950184A0; DE2838789C2; GB2032361B; ES483843A1; FR2435380A1; BR7905715A

Abstract

A steering valve arrangement for a hydraulically operated steering system of a vehicle has two spring-loaded, seated inlet valves 10a and 10b. In such arrangement the supply from a pressure medium source 2 to a respective working chamber 12a; 12b of an adjusting motor 14 is closed in the neutral position of the steering system. The springs 25a, 25b of the seated valves 10a, 10b counteract the force which is generated by the drop of pressure respectively occurring at the seated valves. The arrangement includes two rotary members 22, 23 arranged coaxially one within the other and rotatable in relation to one another upon a steering movement being effected. Upon such steering movement being effected in one direction or the other, the rotary members 22, 23 reduce the force of the valve spring of the seated valve. A centring spring, in the form of a torsion rod 27 is operative between the rotary members 22, 23. In order to obtain a comparatively flat rise in the steering force-pressure characteristic on both sides of the neutral position, there is so connected to the valve spring and in opposition to it, a further spring (fine control spring) that upon a steering movement the rotary members first act on both springs and act directly on the valve spring when the travel of the fine control spring has been used up. The rotary members 22, 23 are constructed as components of a rotary slide valve which forms adjusting throttles 16a, 16b for the working fluid flowing back out of the adjusting motor 14. <IMAGE>

Description

SPECIFICATION Steering valve arrangement for vehicles This invention relates to a steering valve arrangement, wherein the supply from a pressure source is closed in the neutral position of the valve arrangement. In contrast to a steering valve arrangement which requires a constant neutral flow of the working fluid, a steering valve arrangement of the foregoing kind has the advantage that when the steering is not operated, less energy is consumed, due to the absence of circulation losses.

Steering valve arrangements of the foregoing kind are mainly used in hydraulic steeriiig systems-i.e., steering systems in which there is a mechanical connection between the actuating means (steering wheel) and an adjusting motor for the vehicle parts to be steered. In that case hydraulic boosting is required only when the vehicle travels along curves, but not when it is travelling straight ahead, for example on motorways, so that an appreciable amount of energy can be saved when the vehicle travels straight ahead.

The invention can also be applied to hydrostatic steering systems - i.e., steering systems in which there is no mechanical connection between the actuating means and the adjusting motor. It is true that vehicles equipped in this way are not permitted to reach high speeds. Nevertheless, in such case also energy loss due to the circulation of the hydraulic medium should be avoided if a particular steering movement remains unchanged, for example, when a working vehicle performs work with an unchanged steering movement, at rest or in movement.

Steering valve arrangements which are closed in the neutral position are also advantageously used for steering installations having a central hydraulic system, so that the full working pressure is available for other loads, such as brakes or a level regulating system.

Our co-pending Patent Applications (7926972 Serial No 2026964 and 7926973 Serial No. 2026965) relate to a steering valve arrangement which is closed in the neutral position, and more particularly to a construction of seated valves such that the spring chamber of the seated valves is the discharge chamber and the valve spring counteracts the force generated by the drop in pressure at the seated valve, parts of the vehicle actuating means so engaging the valve springs that upon a steering movement the force of the valve spring corresponding to the steering direction is reduced, so that the seated valve can then effect its control function to build up a working pressure in the adjusting motor.

The steering valve arrangements disclosed in these two earlier Applications are intended to produce a bent steering force-pressure characteristic on both sides of the neutral position of the valve arrangement which has a so-called fine control zone, in which with increasing steering force the pressure adjusted in the adjusting motor rises substantially less than in the adjoining cut-off zone, in which considerable rises in pressure correspond to only slight further increases in force. The characteristic therefore first has a relatively flat branch, a steep branch following the cut-off point.

The steering valves have one 6r two inlet seated valves and if necessary one or two outlet seated valves. To produce the fine control zone with flat rise in pressure, a further spring (fine control spring) is provided which acts against the closure spring of the or each seated valve. In co-operation with a centring spring, which is disposed in the train of the actuating means, control is first effected accompanied by relatively large relative displacements or rotations and relatively considerable deflection of the centring spring in the fine control zone, while after the available travel of the fine control spring has been used up control is effected with only slight further travels and rises in force of the centring spring and closure spring of the particular seated valve in the cut-off zone. This applies to both the afore-mentioned Applications.

The pre-characterising clause of claim 1 relates exclusively to the first-mentioned Patent Application 7926972, in which the seated valves are actuated by two members (rotary members) which are rotatable in relation to one another, the seated valve preferably having an arcuate valve spring.

In such case relatively large rotations as between the two rotary members are required for steering in the fine control zone.

The present invention enables these relatively large paths of rotation as between the two rotary members to be utilised to control further functions of the steering valve arrangement. The object is to achieve the functions of discharge adjustment throttles and/or of a working liquid distributor, by which the working fluid is conveyed in a controlled manner to one or other working chamber of the adjusting motor, and the returning liquid to a discharge line.

Accordingly, the present invention consists in a steering valve arrangement for vehicles, having a closed centre and at least one spring-loaded seated valve whose valve spring counteracts the force which is generated by the drop in pressure occurring at the seated valve, and two rotary members arranged coaxially one within the other and which are rotatable in relation to one another upon a steering movement and which upon a steering movement being effected in one direction or the other, reduce the force of the valve spring of the seated valve, a centring spring being operative between the rotary members and, to obtain a relatively flat rise in the steering force-pressure characteristic on both sides of the neutral position, there is so connected against the valve spring a further spring (fine control spring) that upon a steering movement the rotary members first act on both springs and act directly on the valve spring when the travel of the fine control spring has been used up, characterised in that the rotary members are components of a rotary slide valve which forms adjusting throttles for the working The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

fluid flowing back out of an adjusting motor and/or a distributor for the working fluid flowing to and back from the adjusting motor The decisive idea in comparison with our copending Application 7926972 resides in the feature that the rotary members are constructed as rotary slide valves controlling the above-mentioned functions.

The discharge adjusting throttles have the following two functions: 1) The throttle associated with the pressureless working chamber of the adjusting motor enables the working fluid to be discharged as unimpededly as possible.

2) The throttle which is associated with the pressurised working chamber of the adjusting motor enables the working fluid to be discharged in a controlled manner. On the one hand this is required with forces acting from the road on the adjusting motor, such forces being possibly very high, for example in impacts. In such case this pressure chamber must be relieved. On the other hand there are cases in which pressurised liquid must be discharged from the pressurised working chamber, that is when the steering wheel runs back after a steering movement, but the driver brakes or halts such return. Then pressurised liquid still flows into the working chamber as its volume becomes smaller. However, to enable the volume to become smaller, pressure fluid must be able to flow away, and this is made possible by the associated discharge adjusting throttle.

The function of a distributor is required when only one inlet seated valve is provided. In such case the distributor apportions pressurised fluid to one working chamber of the adjusting motor and ensures that the working fluid flowing back from the other working chamber passes to the discharge line. If required the distributor can also interconnect the two working chambers in the neutral position of the valve arrangement.

Lastly, the functions of the discharge adjusting throttles and the distributor can be combined with one another in a rotary slide valve. In such case a rotary slide valve so constructed can on its own perform the complete functions of a steering valve, although in the present case this is used exclusively for an emergency function. The invention relates to a steering valve with a closed centre, wherein the pressurised liquid is prevented from flowing in the neutral position and in a small zone on both sides of the neutral position. This can be done only by a seated valve, but not by a rotary slide valve with its gland, which is liable to leak.However, if the inlet seated valve and/or an outlet seated valve fails, the rotary slide valve can take overthe complete steering function and make operation such that it at least substantially follows the required steering forcepressure characteristic.

According to a further development of the invention, the discharge adjusting throttles are constituted by transverse ducts arranged angularly offset in relation to one another within the two rotary members.

Preferably, the angularly offset transverse ducts are arranged in the inner rotary member.

A further development of the invention relates to a convenient design of a rotary slide valve, which controls the flow of the pressurised liquid from the inlet seated valve to the adjusting motor and from the latter two a discharge, while on the other hand forming discharge adjusting throttles, so that in the afore-mentioned emergency function the work characteristic can be approximated.

Conveniently, incorporated in the return line is an outlet seated valve which can be actuated in the same manner, that is by its valve spring, and also forces an outline of characteristic like the inlet seated valve, although the outlet characteristic is in each case higher by a value Ap than the inlet characteristic, so that a pressure can always reliably build up in the adjusting motor. In this case also the rotary slide valve can have the function of discharge adjusting throttles, although this is important only for emergencies.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example embodiments thereof, and in which: Fig. 1 is a circuit diagram of a hydraulic steering system having inlet seated valves and discharge adjusting throttles, Fig. 2 is a cross-section through a rotary slide valve, on the line ll-ll of Fig. 3, and shows one of the inlet seated valves and one of the discharge adjusting throttles, but without casing, Fig. 3 is an axial section through the rotary slide valve with its casing, Fig. 4 shows the working characteristic of an inlet seated valve, Fig. 5 illustrates in a similar manner to Fig. 2 a modification of the embodiment illustrated in Figs. 2 and 3, Fig. 6 is a hydraulic circuit which corresponds to Fig. 1, but has a single inlet seated valve and a dis tributorwhich also performs the function of discharge adjusting throttles, Fig. 7 is a partial axial section on the line Vll-Vll of Fig. 10 through a rotary slide valve performing the function of the distributor illustrated in Fig. 6, Fig. 8 is a cross-section on the line VIII-VIII of Fig. 9, showing the double inlet seated valve, Fig. 9 is a partial axial section on the line IX-IX of Fig.10, Fig. 10 is a cross-section on the line X-X of Figs. 7 and 9 and shows the four sets of longitudinal grooves which perform distributor and throttle functions, Fig. 11 is a hydraulic circuit corresponding to Fig.

6, but with an additional outlet seated valve, and Fig. 12 shows working characteristics of a circuit as illustrated in Fig. 11.

The steering valve arrangement presupposes constant or only slightly fluctuating supply pressure. As shown in Fig. 1, this pressure is advantageously supplied from a high-pressure pump 2 which automatically reduces its delivery flow when the required high pressure is reached, so that pressurised liquid is delivered only when it is used by the steering system and to make up for leakages. In the case of radial piston pumps with intake control, the pressure can be controlled using a simple valve 4. If a hydraulic accummulator 6 is incorporated in the steering system, a relatively small high-pressure pump 2 can be used, since the accumulator covers brief peaks of consumption in the steering system. The accumulator can also supply further loads and is a standby in case of pump failure.Connected to a delivery line 8 supplied from the high-pressure pump 2 and the hydraulic accumulator are two spring-loaded inlet seated valves 10a,10b whose spring chambers are connected to working chambers 12a, 12b of an adjusting motor 14. In contrastto the conventional arrangement, the springs of the seated valves counteract the pressure in the delivery line 8. Stated more precisely, the valve springs counteract the force which is generated by the drop in pressure occurring at the seated valves. Preferably, the valve springs are constructed in the manner disclosed in our co-pending PatentApplication 7926972.

The spring chambers of the two seated valves 10a, 10b are connected via discharge adjusting throttles 16a, 16b to a reservoir 18 from which the high pressure pump 2 delivers.

As shown in Figs. 2 and 3, the discharge adjusting throttles 16a, 16b are formed by the parts of a rotary slide valve 20 having two coaxial constructional members, of which one is referred to as the inner rotary member 22 and the other as the outer rotary member 23. As disclosed in our Patent Application 7926972, the two rotary members actuate the arcuate valve springs 25a, 25b of the two inlet seated valves 10a, 10b which are disposed in opposite directions, so that upon a steering movement in one direction, only one of them provides the control, the other one providing the control upon a steering movement in the other direction.

The rotary members 22, 23 are connected rotationally fast to a torsion rod 27. A fine control spring 29 acts against each of the valve springs, the result being, as disclosed in detail in the co-pending Application 7926972, a steering power-pressure characteristic 30 (Fig. 4) having a fine control zone (straight line 31) and a cut-off zone (straight line 32). Starting from a force F exerted at the steering wheel (not shown), such force having the value 0 in the neutral position, mechanical steering is effected on both sides of the zero position - i.e., when the vehicle is travelling straight ahead with small steering movements. Only above a predetermined limit force G does one of the inlet seated valves start to set up a pressure in one working chamber of the adjusting motor 14.This is effected during the travel of the fine control spring 29 along the straight line 31 of the fine control zone, that is with a relatively low rise in pressure per increase in force. When the travel of the fine control spring has been used up- i.e., after a pin 34 has abutted a stop pin 36 of the valve spring - only a slight further relative movement takes place between the rotary members 22 and 23. The result is a substantially steeper rise of the characteristic in the zone of the straight line 32 of the cut-off zone.

The rotary members 22,23, which actuate the springs, also form the two discharge adjusting throttles 16a, 16b. While in principle use may be made of fixed throttles, the object of the discharge adjusting throttles is to keep down the loss flow of the pressurised oil discharged.

At its right-hand end 38 (as viewed in Fig. 3) the inner rotary member 22 is connected rotationally fast to the steering spindle and to the torsion rod 27 and is accommodated with provision for rotation with a small clearance in a coaxial blind bore 40 of the outer rotary member 23. The outer rotary member 23 is connected rotationally fastto the lefthand end (as viewed in Fig. 3) of the torsion rod 27 and is pivotably mounted in a coaxial bore 42 of a casing 44. In its left-hand zone (as viewed in Fig. 3) the outer rotary member 23 is constructed as a pinion 46 which serves to drive the rack 48 of a rack and pinion type hydraulic steering system.

The outer rotary member 23 has annular chambers 50a, 50b, each of which receives one of the inlet seated valves 10a, lOb. The annular chambers are sealed off from one another and from atmosphere by ring seals 49. To enable the valve springs 25a, 25b to be mounted, in the zone of each annular chamber the outer rotary member 23 is milled away to such an extent that its width b (Fig. 2) is somewhat smal ler than the diameter of the inner rotary member 22.

Consequently the latter partially projects sideways through rectangular apertures in the outer member 23. Viewed without the inner rotary member 22, the opposite rectangular apertures within each annular chamber co-operate with the bore 40 to form a transverse duct 51 inside the outer rotary member 23. Of the transverse duct 51, Fig. 2 shows only four triangular residual parts outsidethe inner rotary member 22. The important feature here is the resulting control edges 52. The transverse ducts 51 inside the outer rotary member 23 extend parallel with one another.

An obliquely extending transverse duct 54a,54b is provided in the inner rotary member 22 in the zone of each of the annular chambers 50a, sOb. The ducts are disposed angularly offset in relation to one another, that is at an angle a in the direction of one side or the other of a plane of symmetry 56 (Fig. 2), which is an axial plane and extends at right angles to the transverse ducts 51 of the outer rotary member 23. The transverse ducts 54a, 54b are constructed as bores which issue into a coaxial central duct 58 (Figs.

2 and 3) of the inner rotary member 22. The central duct 58 is connected via a left-hand (as viewed in Fig.

3) end face chamber 60, at least one oblique duct 62 and an annular chamber 64 to a discharge port 66.

Pressurised liquid is supplied by the high-pressure pump 2 via a coaxial duct 68 in the outer member 23, a bore 70 and a duct 72 to the inlet seated valves iota, 10b.

The two annular chambers 50a, 50b are connected in known manner (not shown in detail) to the working chambers 12a, 12b of the adjusting motor 14.

With small steering forces within the range O-G of the characteristic shown in Fig. 4 steering is purely mechanical. Within the adjoining fine control zone G - A of the straight line 31, the fine control spring 29 and the valve spring of one inlet seated valve or the other build up pressure in the particular pressure chamber of the adjusting motor. The two parallel transverse ducts 51 of the outer rotary member 23 and the angularly offset transverse ducts 54a, 54b of the inner rotary member 22 so co-operate as prog ressivelyto block communication from one annular chamber, for example 50a, to the central duct 58, while communication between the other annular chamber and the central duct is progressively opened.This enables a pressure to build up in the particular pressure chamber of the adjusting motor without pressurised liquid flowing away again to any appreciable extent and resulting in energy losses, while pressurised liquid can flow away with as low throttling losses as possible to the reservoir from the other working chamber of the adjusting motor.

A modification of the first embodiment.

As shown in Fig. 5, the transverse ducts can also be differently arranged. Two parallel transverse ducts 74 can be disposed at an axial distance in the inner rotary member 22, while disposed in the outer rotary member 23 at the same axial distance are two oblique transverse ducts 76 which in this case also are each angularly offset by an agle a in opposite directions in relation to the plane of symmetry 56.

Otherwise the inlet seated valves are constructed and arranged in the same manner and operation is the same as disclosed hereinbefore.

Second embodiment.

Instead of the two inlet seated valves 10a, Ob operative in opposite directions (Fig. 1), the hydraulic circuit illustrated in Fig. 6 has only one inlet seated valve 80, but it operates with steering movements in both directions. Connected to the inlet seated valve 80 is a distributor 82 which, in dependence on the direction of steering movement, apportions pressurised liquid to one working chamber 12a or the other 12b of the adjusting motor 14 and allows working liquid to flow back into the reservoir 18.

Figs. to 10 illustrate the construction of the second embodiment; elements which are identical or similar to those shown in the preceding Figures have the same references and will not be described in greater detail.

Referring to Fig. 8, the inlet seated'valve 80 is formed by two individual valves which operate in opposite directions, whose seats adjoin the same delivery line 8 and which open to opposite sides. A single annular chamber 50 acts as a joint discharge chamber for the right-hand and left-hand parts (as viewed in Fig. 8) of the inlet seated valve 80. Both share a common arcuate valve spring 84. In dependence on the direction of rotation of the inner member 22, the left-hand or right-hand part of the inlet seated valve 80 can be controlled by a cam 86 via fine control springs 29a or 29b, otherwise as disclosed hereinbefore in connection with Fig. 2 and in our co-pending Patent Application No.7926972.

The outer rotary member 23 of the rotary slide valve 83 has two annular grooves (adjusting motor grooves) 86a, 86b, which are in communication with connections 88a, 88b provided in the casing for the two working chambers 12a, 12b ofthe adjusting motor.

As shown in Figs. 8 and 9, the inner rotary member 22 has a set of longitudinal grooves 90 which open into a groove 91 extending peripherally and into the discharge chamber of the inlet seated valve 80, the inner rotary member 22 also having a second set of shorter longitudinal grooves 92 which are connected via radial ducts 94 to the central duct 58 of the inner rotary member 22. The central duct 58 is connected in the manner disclosed hereinbefore to a return line extending to the reservoir 18.

The outer rotary member 23 also has two sets of longitudinal grooves (Figs. 7 and 10), that is a third set of longitudinal grooves 96a, which are connected via radial ducts 98a to the adjusting motor groove 86a, and a fourth set of longitudinal grooves 96b, which are connected via radial ducts 98b to the adjusting motor groove 86b.

Each of the sets has three longitudinal grooves disposed at identical sector angles. In the neutral position illustrated in Figs.7 to 10 the longitudinal grooves 90 of the first set are blocked off from the longitudinal grooves 96a, 96b of the third and fourth set, while the longitudinal grooves 92 of the second set are connected to the longitudinal groove 96a of the third set and the longitudinal grooves 96b of the fourth set Operation of the second embodiment.

In the neutral position illustrated, and also for some distance on both sides thereof, the inlet seated valve 80 remains blocked. In the adjoining fine control zone (straight line 31 in Fig. 4) one half or the other of the inlet seated valve sets up in its discharge chamber (annular chamber 50) a pressure which operates via the distributor in one working chamber or the other of the adjusting motor 14. While the cam 86 of the inner rotary member 22 actuates, for example the right-hand half of the inlet seated valve, as viewed in Fig. 8, the longitudinal grooves 90 of the first set turn clockwise, so that the associated control edges of the longitudinal grooves 90 and of the longitudinal grooves 96a of the third set allow pressurised liquid to flow so the working chamber 12a.The unpressurised working liquid flowing back from the working chamber 12b passes to the longitudinal grooves 96b of the fourth set, overflows into the longitudinal grooves 92 of the second set, and flows therefrom via the central duct 58 to the reservoir.

If the inlet seated valve 80 fails, the steering system can be controlled by the distributor 82 on its own.

A modification of the second embodiment.

As Fig. 11 shows, an outlet seated valve 100 is included in the discharge line from the distributor 82 to the reservoir 18. The outlet seated valve 100 may be constructed in the same way as the inlet seated valve 80. However, suitable dimensioning of the valve springs 84 and fine control springs 29a, 29b of both valves ensures that the outlet seated valve 100 always holds the balance to a pressure higher by a differential pressure Apthan the inlet seated valve 80. These conditions are illustrated by the characteristics shown in Fig. 12, in which the characteristic 30 corresponds to the inlet seated valve and a characteristic 103 to the outlet seated valve. The characteristic 103 has a straight portion 101 corresponding to the fine control zone and a straight portion 102 corresponding to the cut-off zone. The two straight portions are at a distance of Ap from the straight portions 31,32 of the characteristic 30.

The position and shape of the control edges of the longitudinal grooves 90 in the first set and of the longitudinal grooves 96a, 96b in the third and fourth sets, and also of the discharge longitudinal grooves 92 in the second set are so selected that if the inlet and/or outlet seated valve 90; 100 fails, the distributor approaches the afore-mentioned characteristics. For example, if the inlet seated valve 80 fails, as may occur, for example, due to dirt or rupture of the valve spring, there is an excessive pressure at the distributor, in an extreme case the full pressure of the hydraulic accumulator 6. In that case the distributor sets up in the particular pressure chamber of the adjusting motor a pressure which extends substantially along a characteristic 104 shown in broken lines. If, in contrast, the outlet seated valve 100 fails, a characteristic 106 shown in chain-dotted lines is correspondingly set up by the distributor.

Basically the longitudinal grooves of the first to fourth sets are dimensioned in the same manner for the hydraulic circuits illustrated in Figs. 6 and 11 i.e., independently of whether an outlet seated valve is used or not. However, if an outlet seated valve is used, the discharge throttle cross-sectional areas can be made larger in the neutral position, since of course in all normal operational phases the outlet seated valve ensures controlled discharge. The tolerances can be larger, thus making the rotary slide valve cheaper two manufacture.

Claims

1. A steering valve arrangement for vehicles, having a closed centre and at least one spring-loaded seated valve whose valve spring counteracts the force which is generated by the drop in pressure occurring at the seated valve, and two rotary members arranged coaxiallyone within the other and which are rotatable in relation to one another upon a steering movement and which upon a steering movement being effected in one direction or the other, reduce the force of the valve spring of the seated valve, a centring spring being operative between the rotary members and, to obtain a relatively flat rise in the steering force-pressure characteristic on both sides of the neutral position, there is so connected against the valve spring a further spring (fine control spring) that upon a steering movement the rotary members first act on both springs and act directly on the valve spring when the travel of the fine control spring has been used up, characterised in that the rotary members are components of a rotary slide valve which forms adjusting throttles for the working fluid flowing back out of an adjusting motor and/or a distributor for the working fluid flowing to and back from the adjusting motor.

2. A steering valve arrangement according to claim 1, wherein disposed between the outer rotary member and a casing are two annular chambers, each of which receives one of two oppositely disposed inlet seated valves having arcuate valve spring and each of which forms a discharge chamber of the respective valve, and wherein to form the two oppositely operative discharge adjusting throttles which are associated with each seated valve, the rot ary members each have within each annular chamber a continuous duct extending transversely of the axis of rotation of said members; the two transverse ducts of one rotary member are disposed parallel with one another, those of the other rotary member being disposed axially off-set relative to one another, that is laterally inverted in relation to an axial plane extending in the neutral position perpendicularly to the transverse ducts parallel with one another; the transverse ducts of one rotary member are connected to the annular chamber of the inlet seated valves, those of the other rotary member being connected to a return line; and the transverse ducts of both seated valves form with one another throttles which are opened in the neutral position, while with a steering movement the throttles associated with one seated valve are increasingly opened, those associated with the other seated valve being increasingly closed.

3. A steering valve arrangement according to claim 2, wherein the transverse ducts disposed angularly offset in relation to one another are provided in the inner rotary member.

4. A steering valve arrangement according to claim 1, wherein an inlet seated valve operative in both steering directions is provided, and wherein to form a distributor for the working liquid flowing out of the discharge chamber of the valve ("pressure chamber") to one working chamber or the other of the adjusting motor and the working liquid flowing back from the other, corresponding working chamber, the outer wall of the inner rotary member and the inner wall of the outer rotary member are each formed with two sets of the same numbers of longitudinal grooves, which alternate with one another and are disposed at the same centring angle; one (the first) set of the longitudinal grooves of one rotary member is connected to the pressure chamber, the other (the second) set of longitudinal grooves of such rotary member being connected to a return line; and one (the third) set of longitudinal grooves of the other rotary member is connected to one working chamber, the other (the fourth) set of longitudinal grooves being connected to the other working chamber of the adjusting motor.

5. A steering valve arrangement according to claim 4, wherein the widths of the longitudinal grooves of the first, third and fourth set are such that in the neutral position communications between them are blocked.

6. A steering valve arrangement according to claim 4 or 5, wherein the widths of the longitudinal grooves of the second, third and fourth set are such that in the neutral position communications between them are open.

7. A steering valve arrangement according to any of claims 4 to 6, wherein the longitudinal grooves of the first and second set are provided on the inner rotary member, and an inner chamber of the inner rotary member acts as a return line and is connected to the longitudinal grooves of the second set.

8. A steering valve arrangement according to claim 7, wherein the outer rotary member has two annular grooves which are sealed off from one another and of which one annular groove is connected to one working chamber of the adjusting motor and the third set of longitudinal grooves, while the other annular groove is connected to the other working chamber of the adjusting motor and the fourth set of longitudinal grooves.

9. A steering valve arrangement according to any of claims 4 to 8, wherein incorporated in the return line is an outlet seated valve which is disposed between the rotary members and controls the outlet pressure in both directions of rotation, and the springs of the inlet and outlet seated valve are so adapted to one another that the outlet seated valve always holds the balance to a pressure higher by a differential pressure Ap than the inlet seated valve.

10. A steering valve arrangement for vehicles, substantially as herein described with reference to and as shown in the accompanying drawings.