Spool valve

A spool valve for controlling a twin phaser for coupling a drive member to two driven members and to enable the phase of the two driven members to be varied independently includes a bore operably associated with the twin phaser, fluid channels opening into the bore, and a spool. The spool is received in and is moveable relative to the bore so as to selectively open and close the fluid channels in a predetermined manner, thereby providing a fluid communication between the spool and the twin phaser, and varying a phase of output members relative to an input member. The spool and the fluid channels are configured so that an axial displacement of the spool relative to the bore serves to control a phase of a first output member, and a rotation of the spool relative to the bore serves to control a phase of a second output member.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/IB2012/050078, filed on Jan. 6, 2012 and which claims benefit to Great Britain Patent Application No. 1100632.7, filed on Jan. 14, 2011. The International Application was published in English on Jul. 19, 2012 as WO 2012/095772 A1 under PCT Article 21(2).

FIELD

The invention relates to a spool valve and particularly to a spool valve for controlling a twin phaser operable for coupling a drive member for rotation with two driven members and for enabling the phase of each of the two driven members to be varied independently in relation to the drive member.

BACKGROUND

A twin phaser can be used in an internal combustion engine in the drive train from the engine crankshaft to camshaft lobes operating on two different sets of gas exchange valves of the engine. The two sets may be the intake valves and the exhaust valves, respectively. Alternatively, in an engine with multiple valves per cylinder, both sets of valves may be valves of the same type, e.g., intake valves. The present invention is primarily concerned with the construction of the twin phaser and not with the manner in which the two outputs are used in any specific application.

Various designs of phaser have been proposed in the prior art which are operated mechanically, electrically or hydraulically. The present invention relates to hydraulically controlled phasers, examples of which are vane-type phasers. In vane-type phasers, a radial vane connected to one of two members of which the relative phase is to be varied, separates two working chambers within an arcuate cavity defined by the other member.

Twin phasers that are controlled hydraulically generally need four separate oil feeds, as each of the two outputs requires a hydraulic supply line and a return line. Connecting four oil feeds to the cam phaser is complicated because four sealed interfaces are required between the moving parts on the cam/phaser and the stationary parts on the engine.

The same problem is experienced not only with phasers that are hydraulically operated, i.e., that rely on an external pressure supply, but also with other types of phaser, such as, for example, with phasers that rely on differential pressures in the working chambers of the phaser resulting from torque reversals and clutch type phasers as described in EP1216344.

The term “hydraulically controlled” is intended to include all of these phaser types.

Connecting four oil feeds or control lines to a cam phaser can be achieved using an oil-feed manifold, mounted to the front cover and connected to the front of the cam phaser, as described, for example, in U.S. Pat. No. 6,247,436 and in GB 2,401,150. On occasions, however, there is not the packaging space for this to be achieved, especially in an overhead camshaft application. Furthermore, it may be undesirable in some cases to feed pressurised oil through passageways in the front cover.

It has also previously been proposed to construct the oil feeds so that they pass through the camshaft via grooves and passageways formed in the cam bearings. As is discussed below, this approach also raises certain issues.

FIG. 11 of U.S. Pat. No. 7,610,890 (Mahle) shows four adjacent radial grooves cut into the front camshaft bearing. This proposal requires a very large or long front cam bearing to accommodate the four feeds and enough area for it to still act as a bearing surface.

FIG. 1 of U.S. Pat. No. 7,503,293 (Mahle) shows how the two front bearings in a concentric camshaft can be used to convey oil to a twin phaser. In this layout, there are increased opportunities for leakage as oil can leak out of slots in tube 6 where pin 7 moves. The complexity of this proposal also has cost implications.

FIG. 2 of US 2007/0295,296 (Mahle) shows yet another alternative way of conveying the four oil feeds.

It is preferred for the design of the hydraulic control system to reduce the number of oil feeds to the phaser. For a single-output cam phaser, it has been suggested that if the oil control/spool valve is integrated into the body of the cam phaser (rather than having it somewhere in the cylinder head or cylinder block), then only a single oil feed is required.

U.S. Pat. No. 6,571,757 shows such an integrated spool design for a cam-torque actuated cam phaser where a single spool valve is located on the axis of the phaser and its axial position is controlled by an actuator mounted onto the front cover. By moving the spool valve axially, different oil channels are connected and the phaser advances or retards.

This type of design is suitable for a single-output phaser but it is relatively complex for a dual-output device because the front actuator needs to control the axial position of two in-line spool valves independently. Gaining access to the rear spool valve and being able to package two spool valves in line within the confines of the phaser envelope presents difficulty.

U.S. Pat. No. 7,444,968 shows a twin-spool design for a dual independent torque actuated phaser.

SUMMARY

An aspect of the present invention is to provide a hydraulically controlled twin phaser for mounting on a camshaft in which hydraulic fluid is supplied to control the phaser from the camshaft end of the phaser and in which the phaser can be actuated via a control input from its opposite end to control the phase of the two output members of the phaser independently of one another.

In an embodiment, the present invention provides a spool valve for controlling a twin phaser for coupling a drive member to two driven members and for enabling a phase of each of the two driven members to be varied independently relative to the drive member which includes a bore configured to be operably associated with the twin phaser, fluid channels opening into the bore, and a spool. The spool is configured to be received in and be moveable relative to the bore so as to selectively open and close the fluid channels in a predetermined manner so as to provide a fluid communication between the spool and the twin phaser so as to vary a phase of output members relative to an input member. The spool and the fluid channels are configured so that an axial displacement of the spool relative to the bore serves to control a phase of a first output member, and a rotation of the spool relative to the bore serves to control a phase of a second output member.

DETAILED DESCRIPTION

In an embodiment of the present invention, a spool valve is provided for controlling a twin phaser of the type operable to couple a drive member for rotation with two drive members and for enabling the phase of each of the two driven members to be varied independently relative to the driven member, the spool valve comprising a spool dimensional to be received in the bore which is operable and associated with the said twin phaser, wherein the spool is operable to selectively open and close a plurality of fluid channels in a predetermined manner to provide fluid communication between the spool and the said twin phaser to thereby vary the phase of the said output members relative to the said input member, whereby axial displacement of the spool relative to the said bore controls the phase of one of the output members and rotation of the spool relative to the said bore controls the phase of the other output member

In an embodiment of present invention, a twin phaser is provided for coupling a drive member for rotation with two driven members and for enabling the phase of each of the two driven members to be varied independently in relation to the drive member, wherein the twin phaser comprises a spool valve as described in the preceding paragraph.

In an embodiment of the present invention, a valve mechanism is provided for an internal combustion engine having a twin phaser as described in the preceding paragraph.

In the present invention, a spool valve is used to control the hydraulic connections of two groups of control ports of the phaser, to a supply line and a return line. The valve spool has two degrees of freedom, namely axial translation and rotation. Each degree of freedom serves to control a respective one of the two output members of the phaser. The two degrees of freedom are totally independent of one another, inasmuch as the spool can be rotated when in any axial position and can be moved axially when in any angular position. This allows the position and orientation of a single valve spool to set the phases of both output members of the phaser independently of one another.

In an embodiment of the present invention, the operably associated bore which receives the spool is defined by a sleeve that is rotatably received within the phaser, enabling the components of the spool valve, namely the spool and the surrounding sleeve to be held stationary and moved relative to one another as the remainder of the phaser rotates.

In an embodiment of the present invention, the operably associated bore which receives the spool is defined by the phaser and there is no intermediate sleeve. In this embodiment, the spool rotates in use with the phasers and an actuator (or two separate actuators) is used to vary its axial and angular position relative to the main body of the phaser while the phaser rotates.

Referring toFIG. 1, a spool valve10, according to the present invention, for controlling a hydraulic twin phaser, comprises an outer sleeve12, a valve spool14and a feed sleeve16. The outer sleeve12and the valve spool14are shown to an enlarged scale inFIGS. 2 and 3.

The outer sleeve12is a tube with four annular grooves121,122,123and124on its outer surface. Each of the grooves (121,122,123and124), in use, communicates with a respective one of four control lines of a hydraulic twin phaser, as will be described in more detail below. Ports125,126,127and128in the respective grooves121,122,123and124allow hydraulic fluid to flow between the grooves and the inside of the outer sleeve12when the ports are not covered by the valve spool14.

The valve spool14is formed from a cylinder that fits within the outer sleeve12, the fit of the cylinder being such that it will slide and move axially in the sleeve12, but will prevent fluid flow through any of the ports125to128that are covered at any time by the spool14. The spool has a hollow blind bore141that receives the feed sleeve16at its open end. The cylinder has at its blind end a projection148that can be acted upon by an actuator to set the position of the valve spool14relative to the outer sleeve12.

The outer surface of the valve spool14is formed with three grooves142a,142band142cthat extend over the entire length of the cylinder from one end to the other. These grooves, which will be referred to by the generic reference numeral142, are uniformly circumferentially staggered around the outer surface of the cylinder. The outer surface of the valve spool14is formed with three further axial grooves144(only two of the grooves144aand144bbeing seen inFIG. 3) that extend over only part of the length of the cylinder. The grooves144are similarly distributed uniformly about the circumference of the cylinder and alternate with the grooves142. An opening146in each of the grooves144allows hydraulic fluid to flow into the grooves144from the blind bore141.

In the assembled valve, as shown inFIGS. 4 to 6, the feed sleeve16, through which hydraulic fluid under pressure enters the spool valve assembly10, slidingly fits within the open end of the valve spool14and is held in the outer sleeve12by a circlip162. Annular chambers181and182at opposite ends of the valve spool14communicate with one another at all times through the grooves142, and fluid can escape from the spool valve assembly10through the chamber182to drain into an engine front cover. As shown inFIGS. 4 to 6, fluid can drain into a front engine cover from the chamber182, but it is alternatively possible to have a return line in the camshaft to communicate with the chamber181.

In use, two control lines of the twin phaser controlling a first of the two output members communicate permanently with the grooves121and124, while two further lines controlling the second output member communicate with the grooves122and123.

The control of the first output member of the phaser is effected in the manner shown inFIGS. 4,5and6by an axial displacement of the valve spool14.FIG. 4shows that the ports125and128are covered by the outer surface of the valve spool14. In this position, hydraulic fluid can neither be supplied to nor drained from any of the working chambers associated with the first output member and its phase is therefore hydraulically locked relative to that of the driven member.

Movement of the valve spool14to the right as shown inFIG. 5, results in the ports128being connected to the pressurised grooves144and the ports125being connected to a return path for the hydraulic fluid. In particular, the return fluid enters the chamber181and flows through the grooves142into the chamber182from which it can drain into the front cover of the engine. Conversely, as shown inFIG. 6, movement of the valve spool14to the left causes the ports125to be connected to the pressurised grooves144and the ports128to be connected to the oil drain path via chamber182.

FIGS. 7aand8aare sections through a plane passing through the ports126in the groove122of the outer sleeve12, whereasFIGS. 7band8bare sections through a plane passing through the ports127in the groove123, these ports126and127being connected to the control lines associated with the second output member of the phaser. These Figures show the effect of rotating the valve spool14relative to the outer sleeve12. The three shorter grooves144that are pressurised are shown with solid shading and act as supply grooves while the return grooves142are shown unshaded and provide a drainage path. It can be seen fromFIGS. 7aand7bthat in one angular position of the valve spool14, the ports126are connected to the supply channel144and the ports127are connected to drain channel142causing the phase of the second output member to be varied in one sense. Conversely, as shown inFIGS. 8aand8b, rotation of the valve spool14can result in the ports126being connected to the drain channel142and the ports127to the supply channel144, causing the phase to be varied in the opposite sense.

FIG. 9shows that seals200can be arranged on the outer surface of the outer sleeve12to isolate the control ports from one another as the stator30of the phaser rotates while the outer sleeve12is held stationary.

To avoid the pressure of the hydraulic fluid applying a biasing force to the valve spool14, it is possible, as shown inFIG. 10, to form the feed sleeve316with a blind bore that communicates only with the shorter grooves144through openings317. This avoids changes in the supply pressure affecting the position of the valve spool14.

In the embodiment ofFIG. 11, the feed tube416is formed with a non-return valve417. This allows the working chambers of the phaser to remain under pressure even when the supply pressure drops and prevents any instantaneous high pressures in the phaser overcoming the supply pressure.

In the embodiment ofFIG. 12, the same spring518is used to function as a torsion spring to apply a torque to the valve spool14and as a compression spring to urge the valve spool14to the left, as viewed. It should also be noted that instead of using one or more springs, one can rely on friction and the rotation of the phaser to bias the valve spool rotationally.

FIG. 13shows a cross section through an assembled camshaft40, a twin-vane phaser30, spool valve assembly10and an actuator assembly50. The design of the assembled camshaft40and twin-vane phaser30will not be described herein. The design of twin-vane phasers is furthermore described in, for example, U.S. Pat. No. 6,725,817 and WO 2006/067519.

Likewise, the design of an assembled concentric camshaft, also sometimes referred to as a single cam phaser (SCP) camshaft, is described in several earlier patent documents. Such an assembled camshaft has an outer tube fast in rotation with a first set of cam lobes on which outer tube there is also mounted a second set of cam lobes that can rotate relative to the outer tube. An inner shaft rotatably mounted within the outer tube is connected for rotation with the second set of cams by means of pins that pass through arcuate slots in the outer tube. The inner shaft and the outer tube are connected to the two driven members of the phaser of which the drive member is rotated by the crankshaft. In this way, the phaser allows the phase of each set of cam lobes to be adjusted independently relative to the engine crankshaft.

The spool valve assembly10is concentric with the camshaft axis. Pressurised oil is fed to the spool valve assembly10via a groove24in the front cam bearing and is fed to the inner part of the spool valve assembly via drillings25in the rotor of the phaser.

The actuator50is used to axially displace and to rotate the spool valve relative to its sleeve for independent control of the two pairs of oil feed lines of the phaser that control the respective output members. Such an actuator may take the form of the combined linear-rotary actuator as described in U.S. Pat. No. 5,627,418.

The spool valve assembly10in this embodiment remains stationary while the camshaft40and phaser30rotate relative to it. The spool valve assembly10sits in a close running clearance bore in the cam nose for sealing purposes. Because of this close running clearance and the possible run out of the phaser, it is expected that the actuator50may need to be mounted on flexible mounts52so that the system is not over-constrained.

The internal construction of the phaser, the spool valve assembly10and the camshaft40inFIGS. 14 to 18is essentially the same as that ofFIG. 13. The difference in this embodiment of the present invention is that separate actuators250and260are used for axial displacement and rotation of the valve spool14. The axial displacement actuator250can operate electrically, mechanically, hydraulically or pneumatically and serves only to push on the end of the valve spool14against the action of the return spring18.

The rotation of the valve spool14relative to the sleeve12is effected by a second linear actuator260which is shown more clearly inFIGS. 15 to 17. The end of the actuator260carries a plate262with an elongated slot264that slides over the valve spool14. A pin266projecting from the plate262engages in a slot268(seeFIG. 2) in the end of the outer sleeve12to cause it to rotate relative the valve spool14as the actuator260moves linearly. Furthermore, the rotation of the camshaft40could be used to bias the rotation of the outer sleeve12to one end of its travel.

FIG. 18shows an embodiment that includes a torsion spring39, between the valve spool14and the outer sleeve12to bias the rotation of the spool valve assembly10to one end of its travel. This is an alternative to the modification ofFIG. 12, where the same spring is used to bias the valve spool14both axially and rotationally.

In the embodiment ofFIG. 19, the outer sleeve712is integrated into the actuator assembly750as a one-piece module that is assembled to the engine in a single operation. Such a module could be permanently attached to the inside of the front cover of the engine which would slide into the phaser and the nose of the camshaft40when the front cover is mounted onto the engine.

The embodiment ofFIGS. 20 to 22differs from those previously described in that the outer sleeve is omitted and the bore receiving the valve spool814is defined by the rotor of the phaser830. A mechanism842is provided that allows a twin axial actuator to move the spool valve assembly10axially and rotate it relative to the cam nose. This has the added advantage that the spool valve assembly10is then integrated within the cam phaser830.

The mechanism842has an outer collar843, which can only slide relative to the cam nose. This outer collar843has a helical slot cut844, through which a pin845protrudes and engages with the modified inner valve spool814.

When the outer collar843is moved axially relative to the valve spool814, the pin845rotates in the slot844therefore rotating the valve spool814. When both the outer collar843and the valve spool814are moved axially in unison, the valve spool814will just move axially and not rotate. In this way, two axial actuators can be used to control the axial and rotational position of the spool relative to the cam nose.

It will be appreciated that other types of linear/rotary actuator may be used to move the valve spool relative to the outer sleeve, such as, for example, the use of a stepper motor, air cylinders, or solenoid actuators.

The spool valve assembly10can also be adapted for use with other types of twin phasers. For example, for an axially stacked twin phaser it is advantageous to use a spool having pairs of outputs adjacent to each other.

FIG. 23shows an exploded view of an alternative spool valve assembly910suitable for use with an axially stacked twin phaser. The spool valve assembly910is similar to the spool valve assembly10(described in relation toFIGS. 1 to 3) in that it comprises an outer sleeve912, a valve spool914and a feed sleeve916.

The outer sleeve912is a tube with four annular grooves921,922,923and924on its outer surface. Ports925,926,927and928allow hydraulic fluid flow between the grooves (921to924) and the inside of the outer sleeve912when the ports are not covered by the valve spool914.

The valve spool914is formed from a cylinder that fits within the outer sleeve912, the fit of the cylinder being such that it will slide and move axially in the outer sleeve912but will prevent fluid flow to any of the ports925to928that are covered at any time by the valve spool914. The valve spool914has a hollow blind bore that receives the feed sleeve916through its open end. The valve spool914has a projection948that can be acted upon by an actuator to set the position of the valve spool914relative to the outer sleeve912.

The outer surface of the valve spool914is formed with three grooves942a,942band942cthat extend over the entire length of the valve spool914from one end to the other in a direction parallel to the longitudinal axis of the valve spool914. These grooves, which will be referred to by the generic reference942, are uniformly circumferentially spaced apart around the outer surface of the valve spool914.

Until now, the valve spool914has been similar to the valve spool14described in relation toFIG. 3. However, valve spool914has a different arrangement of grooves formed on its outer surface.

The outer surface of valve spool914is formed with three grooves944(only two of the grooves944aand944bcan be seen inFIG. 23) that extend over only part of the length of the valve spool914. The grooves944are circumferentially spaced apart around the outer surface of the valve spool914and extend in a direction parallel to the longitudinal axis of the valve spool914in an arrangement such that they are inter-disposed between adjacent grooves942. An opening946in each of the grooves944allows hydraulic fluid to flow between the grooves944and the inner bore of the spool.

The outer surface of the valve spool914is also formed with three slots950(only two of the slots950aand950bcan be seen inFIG. 23). The slots950are circumferentially spaced apart around the outer surface of the valve spool914in an arrangement such that they are inter-disposed between adjacent grooves942and aligned with corresponding grooves944in a direction parallel to the longitudinal axis of the valve spool914. An opening952in each of the slots950allows hydraulic fluid to flow between the slots950and the inner bore of the spool.

The outer surface of the valve spool914is also formed with a radial groove954which extends around the circumference thereof and is disposed between the grooves944and the slots950such that it is discrete therefrom. The radial groove954passes through the longitudinally extending grooves942such that they are interconnected therewith.

The feed sleeve916is a hollow tube having a flanged end956. The outer surface of the feed sleeve916has two annular grooves958aand958bextending around the circumference thereof. Each annular groove,958aand958b, has a plurality of openings,960aand960b, respectively, circumferentially spaced apart to extend around the complete circumference of each annular groove,958aand958b.

In the spool valve assembly910, the feed sleeve916, through which hydraulic fluid under pressure enters the spool valve assembly910, slidingly fits within the open end of the valve spool914.

In use, rotation of the valve spool914controls the flow of fluid to and from ports925and926for controlling the first output of the twin phaser and axial motion of the valve spool914controls the flow of fluid to and from ports927and928for controlling the second output of the twin phaser. The radial groove954interconnects the grooves942which act as exhaust channels. Accordingly, for example, when the valve spool914is moved axially towards the flange end956, of the feed sleeve916, fluid can exhaust from annular groove923, of the outer sleeve912, into the radial groove954, of the valve spool914.

FIG. 24shows a cross-section through an axially stacked twin phaser962having two axially stacked output rotors,964and966. The spool valve assembly910is fitted within a cam nose968and, in the position shown, the ports are arranged so that the relevant feed and return channels are aligned for fluid communication with the stacked rotors,964and966.

The spool valve assembly can also be adapted for use with other types of phasers, such as, for example, torque actuated phasers. Torque-actuated phasers require a different fluid circuit compared to the above-mentioned pressure-actuated phasers and therefore require a different spool.

FIG. 25shows an exploded view of a torque actuated spool valve assembly1010, having an outer sleeve1012and a valve spool1014.

The outer sleeve1012is a tube with six annular grooves,1070,1071,1072,1073,1074and1075on its outer surface. Each of the grooves, in use, communicates with a respective one of six fluid control channels of a torque-actuated phaser. Ports1083,1084,1085,1086,1087and1088, in the respective grooves1070,1071,1072,1073,1074and1075, allow fluid to flow between the grooves and the inside of the sleeve1012when the ports are not covered by the valve spool1014.

The valve spool1014is formed from a cylinder that fits within the bore of the sleeve1012, the fit of the valve spool1014being such that it will slide and move axially in the outer sleeve1012but will prevent fluid flow through any of the ports,1083to1088, that are covered at any time by the valve spool1014.

The valve spool1014has an end projection1048that can be acted upon by an actuator to set the position of the valve spool1014relative to the outer sleeve1012.

The outer surface of the valve spool1014is formed with an axial groove1044that extends over only part of the length of the valve spool1014in a direction parallel to the longitudinal axis thereof.

The outer surface of the valve spool1014is also formed with an annular groove1054which extends around the whole of the circumference of the outer surface of the valve spool1014.

In use, with the assembled spool valve assembly, axial groove1044is suitably disposed on the outer surface of the valve spool1014to selectively provide fluid communication between groove1071and annular sleeve grooves1070and1072, via ports1083to1085, respectively. Opening and closing of ports1083to1085in order to selectively provide fluid communication is carried out by rotational movement of the valve spool1014relative to the outer sleeve1012.

Annular groove1054is suitably disposed on the outer surface of the valve spool1014to, in use, selectively provide fluid communication between groove1074and to annular grooves1073and1075, via ports1086to1088, respectively. Opening and closing of ports1086to1088in order to selectively provide fluid communication is carried out by axial movement of the valve spool1014relative to the outer sleeve1012.

FIG. 26is a schematic diagram showing a twin torque actuated phaser circuit1090using a spool valve assembly1010, as described above. A drive member1091has cavities,1092and1093, in which vanes1094and1095, are disposed, respectively.

In use, the circuit1090provides selective fluid communication between the spool valve assembly1010and cavities1092and1093for controlling the angle of the vanes1094and1095. The circuit1090provides the fluid communication through fluid paths1070′,1071′,1072′,1073′,1074′ and1075′, associated with ports1070to1075, respectively, of the spool valve assembly1010.

Unlike a vane type phaser driven by hydraulic pressure, the torque-actuated phaser only requires a pressurised supply of fluid to provide a top-up. The top-up fluid enters the system from fluid supply1097via one way valves1096aand1096b

The angle of the vanes,1094and1095, is controlled by selectively providing a combination of closed and open ports1083to1088, associated with the respective annular grooves1070to1075. This selectively enables fluid to flow through one-way valves1096c,d,eandfsuch that the vanes are able to move towards their required position under the action of the cam drive torques.

Rotation of the valve spool1014relative to the outer sleeve1012controls the provision of fluid communication from annular groove1071to either groove1070or groove1072and thereby controls the angle of vane1094through the associated part of the circuit1090.

Movement of the valve spool1014in an axial direction relative to the outer sleeve1012controls the provision of fluid communication from the annular groove1074to either groove1073or groove1075and thereby controls the angle of vane1095through the associated part of the circuit1090.

FIG. 27is a drawing of an alternative embodiment of a spool valve assembly for use with torque actuated phasers where the top-up feed1097is internal to the valve spool. Referring toFIG. 27, a spool valve assembly1110has an outer sleeve1012and an inner valve spool1114. The outer sleeve1012is the same as that described above in relation toFIG. 25. The valve spool1114is similar to valve spool1014as described in relation toFIG. 25except that it has apertures1147in the axial groove1144and apertures1149in the radial groove1154.

The spool valve assembly1110additionally has an inner fluid feed sleeve1198which is formed from a cylinder that fits within the hollow bore of the valve spool1114in the assembled spool valve assembly1110. The fluid feed sleeve1198also has a hollow blind bore with two sets of ports1199aand1199b. Each set of ports,1199aand1199b, extends around the circumference of the fluid feed sleeve1198and each port extends radially through the wall of the fluid feed sleeve1198.

The sets of ports1199aand1199bprovide fluid communication, as required, between the hollow bore, of the fluid feed sleeve1198, and the annular groove1154and grooves1144, of the valve spool1114, respectively.

Also fitted within the hollow bore of the fluid feed sleeve1198are two one way valves1096aand1096b, wherein a first one way valve1096ais fitted at the open end of the closed bore to selectively allow fluid into the bore and a second one way valve1096bis fitted between the two sets of ports,1199aand1199b, such that it selectively allows fluid in to the second set of ports1199b.

In use, top-up fluid is fed, from a source, into the fluid feed sleeve1198through the one-way valves1096aand1096b. The top-up fluid in then fed to the annular grooves1074and1071, via the set of ports,1199aand1199b, respectively.

FIG. 28shows another alternative embodiment of a spool valve assembly1210suitable for use with twin torque-actuated phasers. Compared to the spool valve assembly1110, as described in relation toFIG. 27, the alternative spool valve assembly1210has an outer sleeve1212with an alternative arrangement having only four annular grooves1270,1271,1272and1723.

Rotational movement of the valve spool1214relative to the outer sleeve1212controls the feeding of fluid from the hollow bore of the inner fluid feed sleeve1198to either annular grooves1270or annular grooves1271, via ports1199band longitudinal grooves1244.

Axial movement of the valve spool1214relative to the outer sleeve1212controls the feeding of fluid from the hollow bore of the inner fluid feed sleeve1198to either annular grooves1272or annular grooves1273, via ports1199a, apertures1249and annular groove1254.

FIG. 29is a schematic diagram showing a twin torque actuated phaser circuit1290using a valve spool assembly1210, as described above in relation toFIG. 28.

Referring to bothFIGS. 28 and 29, a drive member1091has cavities,1092and1093, in which vanes1094and1095, are disposed, respectively.

In use, the circuit1290provides selective fluid communication between the spool valve assembly1210and cavities1092and1093, for controlling the angle of the vanes1094and1095. The circuit1290provides the fluid communication through fluid paths1270′,1271′,1272′ and1273′, associated with ports1270to1273, respectively, of the spool valve assembly1210.

A top-up supply of fluid is supplied into the hollow bore of the inner fluid feed sleeve1198via a one-way valve1096from a fluid supply1097.

The angle of the vanes,1094and1095, is controlled by selectively providing a combination of closed and open fluid paths via ports1199band1199a, aperture1249, longitudinal grooves1244and annular groove1254, and their position relative to the ports in annular grooves1270and1271, and1272and1273, respectively. The paths being determined by axial or rotational movement of the valve spool1214relative to the outer sleeve1212, as previously described.

The advantage of this embodiment is that it has fewer (i.e., four) annular grooves and therefore the spool valve assembly1210is significantly shorter in length than the previously described spool valve assembly1110(seeFIG. 27).