SOLENOID OPERATED VALVE

Abstract: A solenoid operated control valve for use as an inlet and/or exhaust valve in pressure modulator has a flat valve element (30) cooperating with a flat valve seat (28) to control the flow of fluid through the valve. At least a portion of the solenoid armature (10) has opposed parallel flat surfaces and is disposed within a gap (12) defined between parallel faces for movement axially within the gap (12) to operate the valve. The flat valve seat (28) is disposed in the plane of one of the parallel faces and one of the parallel faces is a face (16) of the stator (18). All required settings more particularly magnetic reach, the energised gap and excess valve travel to compensate for wear are set automatically by spacers (t₁, t₂, t₃). The spacers give the required settings directly from their own thickness and not through other component dimensions in combination. This has very important implications for production since the direct spacer automatically gives the required dimension, whereas indirect ones can only be chosen by assembly measurement or selective assembly both of which are expensive.

Description: This invention relates to a solenoid operated hydraulic control valve and more particularly to such a valve for use as an automotive brake pressure modulation valve to maintain optimum adhesion or traction between the tyre for the vehicle and road surface during braking when the wheel shows a tendency to lock. Braking systems incorporating such control are commonly referred to as "anti-lock systems". Anti-lock solenoid valves are known, as for example in European Patent 0 051 965 in which the moving armature is pressure balanced to avoid a large magnetic operating force which requires a large operating current of typically many amps. Also, such valves unlike other valves, require especially tight tolerances for the armature travel or magnetic reach and for circularity and alignment of moving parts. Assembly, setting-up and adjustment is problematic especially in mass production the necessary procedures being complex and costly, especially for high speed valves where the armature travel is small so that even errors measured in ten thousandths of an inch are significant. There is a current trend to supply anti-lock systems on light mass-produced vehicles say, lighter than 2 tonnes GVW, and in this market the size and cost of vehicle parts is of paramount importance. With solenoid valves for light vehicles an unbalanced armature is possible since, with a small fluid flow, small fluid passages are sufficient and the unbalanced pressure areas can be tolerated in respect of forces and operating current. One object of this invention is to provide a solenoid operated hydraulic control valve which is simpler and cheaper to manufacture than conventionalvalves of that type, and more especially, a solenoid operated control valve suitable for use in vehicle anti-lock systems. In accordance with the present invention a solenoid-operated control valve such as disclosed in GB-A-2096283 comprising a valve element and a valve seat, each having a flat surface, the flat surface being co-operable to control a flow of fluid through the valve, wherein at least a portion of the solenoid armature has opposed parallel surfaces and is disposed within a gap defined between parallel faces for movement axially within the gap to operate the valve, wherein the flat surface of the valve seat is disposed in the plane of one of the parallel faces, and wherein one of the parallel faces is a face of the solenoid stator is characterised in that the magnetic reach of the armature is determined by the thickness of first spacing means (t₁) and in that the energised gap between the armature and the stator when the solenoid is energised is determined by the thickness of second spacing means (t₂) disposed in the gap to intervene between the armature and the case of the solenoid stator. The known control valve of GB-A-20962831 has projections on the armature which serve to limit the approach of the valve element to the end walls of the valve chamber. The use of co-operating flat valve elements and an armature which may be a simple washer type armature, give rise only to flatness requirements so avoiding the need for the very accurately fitting armature of the conventional balanced design and the need for accurate concentricity control. In a valve according to the present invention, the armature movement, necessary to give pressure change for a given input electrical signal, and indeed all required settings can be automatically achieved during assembly by the use of spacers in conjunction with flat surfaces. The spacers give the required settings directly from their own thickness and not through other component dimensions in combination. This has very important implications for production since the direct spacer automatically gives the required dimension, whereas indirect ones can only be chosen by assembly measurement or selective assembly both of which are expensive. Preferably, the gap between the said parallel faces is defined by a separator ring having the same thickness as the said portion of the armature and the first spacing means, the thickness of which determines the magnetic reach of the armature. Hence the armature and the separator ring are conveniently produced (ground) together so that they have precisely the same but not necessarily an accurately defined thickness, the magnetic reach being accurately and directly determined by the thickness of the first spacing means. The second spacing means directly determines the gap between the armature and the stator when the solenoid is energised. In the preferred embodiment, the armature is assembled to a locating abutment or facepiece separated by third spacing means whose thickness is the distance between the valve element face and one of the armature faces to produce excess travel of the valve element relative to the armature travel thus ensuring contact between the valve element and valve seat, up to a wear level equal to this excess, in the no flow condition. The flat valve element may be a simple disc or the like, the element is carried by the armature in an assembly including a spring or other biasing means urging the element against a locating abutment such that when not in contact with the valve seat, the flat valve element lies substantially parallel thereto. A valve according to the present invention may be of a normally open configuration as used for the inlet/delivery valve of an anti-lock pressure modulator or a normally closed valve as used for the exhaust valve of a pressure modulator. Indeed, both the inlet/delivery and exhaust valve of a pressure modulator may be valves in accordance with the present invention although it is possible to have a combination of an unbalanced inlet valve in accordance with the invention and a balanced exhaust if this is required. As stated above, there is no requirement for an accurately fitting armature and tight concentricity control. In the case of a normally closed valve according to the invention therefore, the valve element of disc can be initially unseated when the solenoid is energised, by being raised at one edge. Such lever action reduces the total pull required to lift the valve against pressure head. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic cross-section of a solenoid operated hydraulic control valve having a normally open configuration and suitable for use as the delivery or inlet valve of a pressure modulation valve of an anti-lock system; Figure 1A is a view on X-X in Figure 1; Figure 2 is a diagrammatic cross-section similar to Figure 1 but of a normally closed valve suitable for use as the exhaust valve of a pressure modulation valve; Figure 3 is a cross-section of a pressure modulator incorporating inlet and exhaust valves as shown in Figures 1 and 2; Figure 4 is a cross-section of a pressure modulator having an inlet valve in accordance with the present invention and an exhaust valve of conventional balanced design; Figures 5 and 6 show separate inlet and exhaust valve assemblies in accordance with the invention; Figures 7 and 8 show stackable inlet and exhaust valve assemblies in accordance with the invention; Figure 9 is a cross-section of a pressure modulator built of the inlet and exhaust valve assemblies shown in Figures 7 and 8; and Figure 10 is a cross-section of another configuration of pressure modulator built of the inlet and exhaust valve assemblies shown in Figures 7 and 8. The normally open inlet/delivery valve shown diagrammatically in Figure 1, includes a flat washer like armature 10 which is disposed within a gap 12 defined between a flat annular face 16 of a solenoid stator 18 presenting poles 18a, 18b and a flat annular face 20 parallel to the stator face 16, presented by an end piece 22 of the valve as will be described below with reference to Figure 3. The end piece 22 is spaced from the stator 18 by an intervening ring 24 having the same thickness as the armature 10, and a spacer the thickness t₁ of which is selected to determine the magnetic reach of the solenoid and is typically of the order of 0.006 inches. A valve seat 26 mounted in the stator has a flat surface 28 that lies in the plane of the stator face 16. The armature 10 forms part of an armature assembly including a floating-valve element or disc 30 for co-operation with the valve seat 26, which is received within the bore of a guide bush 32 securely held to the armature 10 and spaced from it by intervening spacers t₂ and t₃. As will be seen from Figure 1A, the guide bush 32 has a bore 34 within which the valve seat 26 is received and from which emanate three equally angularly spaced radial grooves 36 extending axially of the guide bush 32. A cup 38 having a circumferential corrugation 40, and inserted into a central hole 42 in the armature 10, is located by abutment of the corrugation with the lower side of the armature 10. Tags 44 extending from the lip of the cup 38 pass through the radial grooves 36, the ends 46 thereof being bent over the top of the guide bush 32 to secure the assembly. The lower flat surface of the guide bush provides an abutment for the floating valve element or disc 30 which is housed within the cup 38 and loaded by a spring 48. A spring 50 disposed within the annular solenoid stator 18 around the valve seat 26 biases the armature assembly away from the annular solenoid stator face 16 toward the normally open position illustrated, wherein the armature engages the flat face 20 of the end piece 22 and a flowpath is provided for the flow of fluid from an inlet (not shown) in the end piece through the valve seat 26. The flow path as indicatad in Figure 1 is through a ring of holes 52,54 in the armature and spacer t₂ and equally angularly spaced radial grooves 56 in the guide bush 32, these grooves 56 being interspersed with, but deeper, than the grooves 36. The normally closed exhaust valve shown in Figure 2 is of closely similar construction but in this case, the arrangement is inverted. A return spring 50 which surrounds the cup 38 projecting from one side of the armature 10 biases the armature assembly away from the flat annular face 16 of the solenoid stator presenting poles 18b and 18c, into contact with a flat face 20 of the end piece 22. In this position, the floating valve element 30 or disc engages the flat valve seat 26 which lies in the plane of the end piece face 20. When the valve opens upon energisation of the solenoid, fluid flows from within the annular solenoid stator 18, through the ring of holes 52,54 in the spacer t₂ and armature 10, through the radial grooves 56 and into and through the valve seat 26. In each of the above described valves the diameter of spacer t₂ is such as to prevent contact of the armature 10 with the solenoid stator 18 when the solenoid is energised. The spacer t₂ thus determines the so-called energised gap and is selected to give optimum magnetic decay during armature release. It is typically in the range 0.0015 - 0.002 metres. Spacer t₃ determines the valve disc overtravel available which accomodates seat/disc wear and erosion. The amount of lift l₁ permitted between the valve element or disc 30 and the seat 26 is determined by the construction and given by l₁ = t₁-t₂-t₃ . The armature travel l₂ is given by l₂ = t₁ - t₂ . It will be seen that the dimensional setting up of the delivery valve (Figure 1) is achieved to within a specified band by the use of the three spacers t₁, t₂ and t₃ each of which will incur its own thickness tolerance. The same reasoning applies to the exhaust valve (Figure 2) but because the valve is normally closed the spacers are positioned accordingly and the armature return spring 50 is rated appropriately together with the operating coil (not shown). The valve shown in Figure 3 is a complete pressure modulator for use in an anti-lock brake system and incorporating an inlet delivery valve as described above with reference to Figures 1 and 1A and an exhaust valve as described with reference to Figure 2. The inlet and exhaust valves having respective solenoid coils 58,60 and a common solenoid core or stator assembly 18a, 18b, 18c are housed within a container 62. Pressurised fluid supplied from the brake valve (not shown) enters port 64 through filter screen 66i and, when there are no electrical modulation signals in coil 58, passes this inlet valve disc 30i which is normally lifted from the seat 26i by the spring 50i and then passes through port 68 to operate the brakes. A seal 70i whose bore dimension is such as to contain the axial bursting force under high fluid pressure within exceeding the external pressure force over seal, avoids unnecessary axial working force on the outside container 62. The same arrangement is used at the exhaust valve end in respect of seal 70e, but the external pressure force is only over the annulus between the delivery seal and return seal, giving a resultant force loading the modulator towards its delivery/exhaust manifold. This avoids any requirements for accurate manifold spacing particularly where several modulators with height variation are together. To ensure correct operation of the delivery and exhaust valves for the purpose of modulating pressure the following manufacturing requirements must be met together with the correct choice and fitment of spacer t₁, t₂ and t₃ (see Figures 1 and 2). The armature 10 and ring 24 (both ends of modulator) must have the same thickness with both faces parallel and flat, if the two components are produced together in batches the thickness may have an open tolerance. The face of the guide bush 32 for contact with the valve element 30 (both ends of modulator) must be flat. Both ends of the solenoid core or stator 18, must be flat (but no accuracy is required on parallelism) and additionally the flat face 28 of valve seat 26 must have the required valve seat finish which can be obtained by lapping after it has been pressed into its mounting i.e. stator portion (delivery valve) or end piece (exhaust valve) to give a slight protrusion. This protrusion may result from elastic retrieval following the use of a flat anvil pushing the seat into its mounting, or it may be achieved by the use of jigs. The faces of the two end pieces 22 must be flat. There are no important concentricity requirements for the armatures 10i, 10e but they are guided by the location of guide bush 32i,32e sliding over the valve seat 26i,26e. In the unenergised state i.e. no voltage applied to coil, 58 the inlet valve is open. On receiving a voltage signal, the coil 58 generates a magnetic pull between the stator poles 18a, 18b urging the armature 10i to the valve closed position, complete contact between the poles 18a, 18b and armature 10i is prevented by spacer t₂ (the energised gap) which is adjusted (selected) to ensure a fast drop-out over armature return when the voltage is removed to open the valve. The small annular gap between the stator poles 18a, 18b and 18b, 18c is adjusted to achieve a fast decay of magnetic flux without impairing pull-in performance. Seals 72i, 72e are incorporated to contain the pressurised fluid and the complete valve assembly is contained by the rolled over tube 62 which deals with handling forces predominantly. The exhaust valve is normally closed, (see also Figure 2) and when a voltage signal is applied to the coil the valve disc lifts allowing fluid from the brakes to pass through the second screen filter 66eand return to the reservoir. The valve movements are determined by the spacer t₁, t₂ and t₃ as with the inlet valve, but they are located to suit the normally close configuration. It is a basic requirement that braking systems release the brakes when the brake pedal effort is removed and if an anti-lock modulator is in the 'hold' state (i.e. inlet and exhaust valve closed with pressure in brakes) then the electric signal to the inlet valve prevents this happening. To avoid this situation in conventional valves, a separate one-way valve is fitted. The one way feature is automatially achieved in the inlet valve of Figures 1 and 3, by the inlet valve disc 30 since under the lightly loaded spring 48 it cannot sustain pressure at the delivery unless there is pressure at the inlet. The construction of the armature 10e and exhaust valve disc 30e is such that during magnetic pull the armature can tilt because of the diametral clearance between the valve seat 26e and guide bush 32e and slight uneveness of the magnetic flux due to eccentricity between the bore and outside diameter of armature 10e with the result that the disc 30e is levered from the seat 26e whilst under fluid pressure (typically 170 bars) thereby minimising the magnetic pull required. Since magnetic pull is time growth dependent a faster valve response results. The modulator of Figure 4 includes an inlet valve as described with reference to Figure 1 except that it is inverted with fluid supplied from the brake valve through the valve seat so that the non-return feature is absent, and balanced exhaust valve similar to that described in our European Patent 0 051 965. Pressurised fluid from the brake valve enters at port 100 and flows through chamber 102 towards normally open valve 104. The coil 106 can modulate this valve in the same manner described for the inlet valve of Figures 1 and 3. The fluid passes through chamber 108 either to the brakes via port 110 or to reservoir via port 112 if valve is modulated. The opening of normally-closed valve 114 is achieved by coil 116 lifting armature 118 the spool diameter of which is the same as the valve seat diameter preventing an axial pressure force acting thereon. Figures 5 and 6 show separate delivery and exhaust valve assemblies arranged for bolting to a surface recess. Each valve is contained within a housing having a flange through which four bolts (one shown) pass to secure the assembly and support the axial pressure load. The exhaust valve of Figure 7 is equivalent to the valve of Figure 6 except a cover plug is incorporated such that a delivery valve such as shown in Figure 8 may be stacked with it to form a complete modulator as shown in Figure 9. This delivery valve in Figure 8 is equivalent to the valve of Figure 5 except that a cover plug is incorporated for stacking. The valve may be stacked as shown in Figure 9 which provides the non-return valve function previously described or it may be inverted as shown in Figure 10 to omit the non-return valve function. The assemblies of Figures 9 and 10 offer complete modulation like the unit of Figure 3, but additionally the valve may be used separately and are therefore rationalised designs.

Claims: A solenoid-operated control valve comprising a valve element (30) and a valve seat (26), each having a flat surface, the flat surfaces being co-operable to control a flow of fluid through the valve, wherein at least a portion of the solenoid armature (10) has opposed parallel surfaces and is disposed within a gap (12) defined between parallel faces (16, 20) for movement axially within the gap to operate the valve, wherein the flat surface of the valve seat is disposed in the plane of one of the parallel faces, and wherein one of the parallel faces is a face of the solenoid stator (18), characterised in that the magnetic reach of the armature is determined by the thickness of first spacing means (t₁) and in that the energised gap between the armature (10) and the stator (18) when the solenoid is energised is determined by the thickness of second spacing means (t₂) disposed in the gap (12) to intervene between the armature (10) and the face (16) of the solenoid stator (18). A valve according to claim 1 wherein the gap (12) between the said parallel faces (16, 20) is defined by a separator ring (24) having the same thickness as the said portion of the armature (10), and the first spacing means (t₁) the thickness of which determines the magnetic reach of the armature. A valve according to claim 1 or claim 2, having third spacing means (t₃) whose thickness defines the distance the valve element face and one of the armature faces to produce excess travel of the element relative to the armature travel, whereby wear or erosion of the valve element (30) and/or the valve seat (26) is compensated. A valve according to any preceding claim, wherein the valve element (30) is tiltable with respect to the valve seat (26) when being lifted therefrom. A valve according to any preceding claim, wherein the valve element (30) is movably mounted to the armature and biasing means (48) are provided to urge the valve element into contact with the valve seat (26). A valve according to any preceding claim wherein, when not in contact with the valve seat (26), the valve element (30) is restrained by being urged into contact with a locating member (32) such that the flat surface of the valve element (30 is kept substantially parallel to the flat surface of the valve seat (26). A valve according to any preceding claim wherein the armature (10) is biased away from the face of the stator (18) so that, when the solenoid is inactive, one of the flat surfaces of the armature abuts the face parallel to the face of the stator. A valve according to claim 7, wherein the face of the stator (18) faces in the opposite direction to the flat surface of the valve seat (26), so that the armature (10) and the valve element (30) are urged towards the valve seat (26) whereby the valve is closed when the solenoid is not energised. A valve according to claim 7, wherein the face of the stator (18) faces in the same direction as the flat surface of the valve seat (26), so that the armature (10) and the valve element (30) are urged away from the valve seat (26) whereby the valve is open when the solenoid is not energised. A valve according to any preceding claim which may be arranged to adapted to invert the fluid flow path within. A valve according to any preceding claim adapted to be attached to a surface recess by attachment means such as bolts. A pressure modulator having an inlet/delivery valve according to claim 9 and an exhaust valve according to claim 8. A pressure modulator according to claim 12, wherein the valves each have a solenoid coil and each valve shares a common solenoid stator. A pressure modulator according to claim 12, wherein the valves are stackable to form the modulator but may be used separately. A pressure modulator having an inlet/delivery valve according to claim 9 and a balanced exhaust valve.

Inventors: HAWKER, MICHAEL JOHN
Applicants: WABCO AUTOMOTIVE U.K. LIMITED
Application year: 1988
Main classification: B60T8
IPC codes: B60T8, B60T15, F16K31