SOLENOID VALVE ASSEMBLY

Abstract: A valve assembly (10) having normally-open and normally-closed valves (88,96) selectively controlled by solenoids (16,18) to provide various connected and disconnected arrangements between a pressure inlet (148) and a pressure outlet (126) to provide four possible modes of operation in a fluid system, namely a pressure-apply mode, a pressure-hold mode, a pressure-release mode and an air-bleed mode. It is particularly useful in a wheel lock control or anti-skid brake system (ABS).

Description: The invention relates to a valve assembly having valves controlled by solenoids to provide various connected and disconnected arrangements in a fluid system as specified in the preamble of claim 1, for example as disclosed in EP-A-0 256 272. It is particularly useful in a wheel lock control or anti-skid brake system (ABS). A solenoid valve assembly according to the present invention is characterised by the features specified in the characterising portion of claim 1. The two solenoid control valves are preferably placed in a single package and arranged in geometric series connection. The valve assembly preferably has four functional modes with three fluid ports. The four functional modes are controlled by energizing or de-energizing the solenoids in various combinations. When used in a wheel lock control or anti-skid brake system there is a pressure-input port, a pressure-output port, and a pressure-release port or exhaust port which releases fluid directly to a reservoir. The fluid connection between the input port and the output port, and the fluid connection between the output port and the pressure-release port, are within the valve assembly. The assembly preferably has a common chamber made of two thin-walled stainless steel tubes and a centre-channelled plunger stop to which the two tubes are attached at each end thereof. The channel arrangement provides the shortest fluid passage from the pressure-output port to the pressure-release port within the valve assembly whilst having a minimum fluid energy loss. It is another feature of the invention that the electrical connection and the direction of the coil windings of the two solenoids assist in forming a continuous enhancible magnetic flux pattern so that the resulting magnetic fields can provide enhanced performance. It is a feature of the invention that the centre thin-wall stainless steel tubes act as chambers which contain the valve plungers, which are also solenoid armatures, with pressurized fluid being within the tubes under certain conditions. The arrangement avoids axial loading against the thin-wall tubes and the tubes are strengthened so as to contain the fluid pressure therein by the position of the solenoid coils and coil housings immediately about each tube. It is another feature of the invention to provide a triple cascade orifice configuration to function effectively and quietly in high-pressure application. The triple cascade orifice is positioned between the pressure-input port and the pressure-output port and includes three orifices provided in series, the third orifice being established by an opening between a ball valve and a cylindrical wall in which the ball valve is located when the ball is unseated so as to permit flow therepast. This arrangement provides sufficient fluid flow at highly compressed fluid pressures with the least pressure differential across each of the individual orifices, tending to eliminate fluid cavitation and to alleviate induced noise resulting therefrom. IN THE DRAWING: Figure 1 is a cross-section view with parts broken away showing a solenoid valve assembly embodying the invention. Figure 2 is an enlarged fragmentary portion of Figure 1 as indicated by circle 2 on Figure 1. A solenoid valve assembly 10 according to the present invention is illustrated in Figure 1 as having a housing section 12 which includes an electrical connector 14. It also houses two solenoid assemblies 16 and 18 as well as at least portions of the valves and fluid passages controlled thereby. Assembly 10 also includes a housing section 20 which houses a portion of the solenoid assembly 16 as well as a normally-open valve controlled by that solenoid. The two solenoids are illustrated as being contained within a solenoid case assembly 22. The solenoid assemblies 16 and 18 are also associated with end plates 24 and 26, respectively, as well as a centre plunger stop support plate 28. Solenoid coil frames 30 and 32, respectively containing solenoid assemblies 16 and 18, engage the plates 24, 26 and 28 and co-operate therewith to bear the axial load in compressive-loading conditions so that the axial load is not carried through a solenoid coil 34 of solenoid assembly 16 or a solenoid coil 36 of solenoid assembly 18. The direction of coil windings in said solenoid coils 34, 36 and the direction of electrical current flowing through one of said solenoid coils when only the one of said solenoid coils is electrically energized are such that any magnetic field of said one electrically energized solenoid coil which influences an armature plunger of the other of said solenoid coils acts on that armature plunger to urge it in the axial direction opposite to the axial direction in which that armature plunger is magnetically urged by the other of said solenoid coils when said other solenoid coil is electrically energized. Moreover, the direction of coil windings in said solenoid coils 34, 36 and the direction of electrical currents flowing therethrough when both of said solenoid coils 34,36 are electrically energized are such that the magnetic flux patterns thereof at their adjacent ends enhance each other. Solenoid assembly 16 has one end 38 of case assembly 22 crimped over a flange 40 of a normally-open valve housing 42. The other end 44 of case assembly 22 is similarly crimped about a flange 46 of a solenoid assembly cap 48. Cap 48 is illustrated as being provided with a multiple land sealing grommet 50 which extends through a tube-like bottom portion 52 of a reservoir 54 so that an upper end 56 of cap 48 opens into the reservoir 54 and the grommet 50 effectively seals between the cap 48 and the reservoir portion 52. Reservoir 54 is preferably the reservoir for a master cylinder and a booster of a brake system as well as for an ABS system of which the solenoid valve assembly herein disclosed and claimed is preferably a part. Plunger stop assembly 58 includes a stop 60 and stainless steel tubes 62 and 64. Stop 60 has a through passage 66 formed axially therethrough and having slightly enlarged passage ends 68 and 70. A spring 72 is positioned in passage end 68 and abuts a shoulder formed at the bottom portion thereof. Another spring 74 is similar positioned in passage end 70. A centre portion of plunger stop 60 is suitably slotted or grooved so as to receive at least a part of plate 28 therein to anchor and locate the plunger stop assembly 58 axially and radially. An outer end 76 of tube 62 extends into the valve housing 42, and an outer end 78 of tube 64 extends into the solenoid assembly cap 48. The cylindrical spaces outwardly of the plunger stop 60 and the ends 76 and 78 of the stainless steel tubes provide cylinders. The inner ends of the stainless steel tubes 62 and 64 are secured to the plunger stop 60 in any suitable manner, for example by welding. The electrical connector 14 has suitable terminals and connecting wires arranged for energization and de-energization of each of the solenoid coils 34 and 36. These coils are wound in opposite directions for reasons to be described hereinafter. Solenoid assembly 16 has a solenoid armature plunger 79 which is reciprocably received within tube 62 and has axially-extending passages 80 which permit fluid flow therepast. Spring 68 is in engagement with an inner end 82 of plunger 79 so as to urge that plunger outwardly of the tube 62. A rod 84 has one end secured to plunger 79, with the other end extending outward of tube 62 and into a portion of the valve housing 42. Rod 84 is provided with a head 86 which controls the condition of a normally-open valve 88, described in greater detail below. Solenoid assembly 18 has an armature plunger 90 reciprocably received for axial movement in tube 64. Spring 74 engages plunger 90 and urges that plunger outwardly of tube 64. Plunger 90 also has a passageway 92 formed therethrough which is in continuous fluid communication with passage of the plunger stop 60. Plunger 90 is formed to provide a valve head 94 which is a part of a normally-closed valve 96. A seat member 98 is sealingly mounted in the outer end 78 of tube 64 and has a restrictive orifice passageway 100 formed therethrough. The end of passageway 100 facing valve head 94 is formed as a valve seat 102, and valve head 94 is normally in engagement with valve seat 102 to maintain passageway 100 closed. The seat member 98 is provided with a seal 104 which prevents leakage between the seat member and the inner wall of tube 64. The other end of seat member 98 is engaged by the inner end of a plug 106 which is threaded into cap 48 so as to provide the appropriate axial position of seat member 98. Plug 106 has a recess 108 formed therethrough in continuous fluid communication with passageway 100. The upper end of recess 108 is provided with a port 110 which is the release port of the assembly. Port 110 opens into the interior of reservoir 54. It can be readily seen that any fluid passing through passageway 100 and recess 108 will then be discharged directly into the reservoir. Valve housing 42 has a centre wall 112 provided with a passageway 114 extending axially therethrough. Rod 84 extends through this passageway but is somewhat smaller in diameter than the diameter of the passageway so that fluid communication is maintained between the interior of tube 62 and the other side of the centre wall 112. On the other side of wall 112 is located the rod head 86 which is axially spaced slightly from that wall. A plug 116 is inserted in an outer opening 118 of valve housing 42 and limits axial outward movement of the valve head 86. Plug 116 has a passage 120 extending axially therethrough, with a filter 122 held in the outer end of passage 120 by a retainer 124. Thus passage 120 is connected through the filter 122 to a pressure output port 126 provided in a part of housing section 20 in which the valve housing 42 and the plug 116 are mounted. The valve housing centre wall 112 is of a decreased diameter in relation to valve housing ends 128 and 130 so that an annular chamber 132 is formed thereabout, this chamber being defined on its outer circumference by a portion of a cylinder wall 134 of a cylinder-like recess in housing section 20 into which the valve housing 42 is mounted. Suitable seals 136 and 138 are respectively provided on valve housing ends 128 and 130 so as to seal the annular chamber 132 relative to the pressure-output port 126 and the portion of housing 20 containing a part of the solenoid assembly 16. As shown more clearly in Figure 2, an L-shaped passage 136′ is formed in the valve housing centre wall 112 with one end 138′ opening into the annular chamber 132 through a first orifice 140 formed in an orifice plate 142. Plate 142 is mounted in the end 138′ of passage 136′. An annular filter 144 is secured in the annular chamber 132 so that all fluid flowing from the chamber into passage 136′ first passes through that filter. It is noted that annular chamber 132 is in continuous fluid communication with a passage 146 in housing section 20 which is directly connected to a pressure-input port 148. Thus operating pressure is supplied to the valve assembly via pressure-input port 148 and is always presentin the annular chamber 132. Passage 136′ has another portion thereof formed to provide a second orifice 150 which extends parallel to the axis of the valve housing 42 and opens to provide a tapered valve seat 152 and a valve cylindrical wall 154, which in turn is fluid-connected to the passage 120 and pressure-output port 126 through filter 122. The normally-open ball-check valve 88 (axially spaced from the solenoid 16) is positionally retained within a cylindrical wall 154 so as to be engageable with tapered valve seat 152. When the rod head 86 is positioned downwardly as seen in Figure 1, solenoid coil 34 being de-energized, the head is sufficiently spaced from the centre wall 112 to permit the ball-check valve 88 to be spaced from its seat 152 and therefore to permit flow through the passage 136′ including orifices 140′ and 150 and an orifice 156 defined by the annular space around the ball-check valve 88 and the surface of cylindrical wall 154. When the solenoid coil 34 is electrically energized, it acts on plunger 79 to move the rod 84 and the head 86 upwardly as seen in Figure 1 to force valve 88 into engagement with the valve seat 152, holding the valve closed. Another L-shaped passage 158 in the valve housing centre wall 112 connects the annular chamber 132 with the pressure-output port 126 at all times. Ball-check valve 160 prevents reverse flow from the annular chamber 132 to the pressure-output port 126. A portion of passage 158 adjacent the valve seat of ball-check valve 160 is an orifice which will permit flow from the pressure-output port 126 to the pressure-input port when the pressure at the pressure-output port 126 is trying to be at a greater value than that of the input port. Thus valve 160 and passage 158 prevent the pressure at the pressure-output port 126 from being greater at any time than that of the pressure at the pressure-input port 148. The three orifices 140, 150 and 156 between the pressure-input port 148 and the pressure-output port 126 provide a triple cascade orifice configuration which functions effectively and quietly in high pressure applications. At the same time it permits a sufficiently high fluid flow at highly compressed fluid pressures with the least pressure differential across each individual orifice, hence minimizing fluid cavitation and alleviating noise induced from such cavitation. The normal, de-energized, position of the valves in the assemblies is the position for normal pressure applied from the pressure-input port 148 to the pressure-output port 126 through the normally-open valve 88. This occurs when both solenoid coils 34 and 36 are de-energized so that valve 88 is opened and valve 96 is closed. Input pressure will also be conducted through the passageway 114 and past plunger 79, into passage 66 and passageway 92. However, the normally-closed valve 96 prevents that input pressure from being conducted to the reservoir 54 through port 110. In the output pressure hold mode the solenoid coil 34 controlling the normally-open valve 88 is energized, moving plunger 79 towards plunger stop 60, and moving rod head 86 so that it engages the ball valve 88 and moves that valve, holding that valve seated against the valve seat 152. This therefore closes off the input pressure in port 148, and holds the output port pressure in port 126 to the pressure therein at the time valve 88 was closed. Since valve 96 remains closed, the pressure in the output port 126 neither decreases nor increases. When the pressure in the output port is to be released to a lesser pressure, or even to zero pressure, the solenoid coils 34 and 36 are both energized, closing or keeping valve 88 closed as in the previous state, and moving plunger 90 toward the plunger stop 60 to open valve 96. The output port pressure is then connected through passage 120 and passage way 114 as well as passage 66 and passageway 92 to the restrictive orifice passage 100 which controls rate of flow of fluid therethrough, after which the fluid enters the reservoir 54 through the release port 110. The pressure apply mode may be re-instituted by de-energizing both solenoid coils, returning the valves to their respective normally-open and normally-closed positions. When there is trapped air in the system a trapped air bleed mode is established by de-energizing coil 34, if it is energized, and energizing coil 36. This opens both valves 88 and 96, allowing the system to be bled, with the flow of fluid under pressure from the input port assisting in flushing any trapped air out of the assembly. Once the assembly is bled, both solenoids are then normally de-energized to return the assembly so that it may again permit the application of pressure from input port 148 to output port 126.

Claims: A solenoid valve assembly (10) having a housing (12,20), a pressure inlet (148), a pressure outlet (126), an exhaust port (110), a first solenoid (16) having a first solenoid-actuatable plunger (79); a second solenoid (18) having a second solenoid-actuatable plunger (90) in axial alignment with said first solenoid (16) and plunger (79); a plunger stop and guide member (58) comprising a stop element (60) positioned axially intermediate said plungers (79,90) and tubular guide means (62,64) secured to and extending from said stop element (60) with said first plunger (79) and said second plunger (90) being respectively reciprocably received therein, said stop element (60) having an axially-extending bore (66) therethrough; a first valve housing (42) having normally-open first valve means (88) therein, axially-spaced from said first solenoid (16) and positioned in a fluid circuit intermediate said pressure inlet (148) and said pressure outlet (126) and having a valve-closing member (86) secured to said first plunger (79) and movable therewith when said first solenoid (16) is energized to close said first valve means (88); passage means (114) in said first valve housing (42) in axial alignment with said first plunger (79) and maintaining continuous fluid communication between said pressure outlet (126) and said axial passage (66) in said stop element (60) through said first tubular guide (62); and normally-closed second valve means (96) including a valve seat (102) in said second tubular guide (64) in axially-spaced relationship to said stop element (60) with said second plunger (90) positioned axially therebetween, a valve element (94) formed on said second plunger (90) and normally seated on said valve seat (102) to close said second valve means (96) and being axially movable when said second solenoid (18) is energized to open said second valve means (96), said second plunger (90) providing fluid communication with said stop element axial passage (66) to said valve element (94), and a restrictive orifice passageway (100) extending through said valve seat (102) and in fluid communication with said exhaust port (110); said solenoids (16,18) being selectively energizable and de-energizable to selectively open and close said first and second valve means (88,96) and thereby control the fluid pressure in said pressure outlet (126) in pressure-apply, pressure-hold, pressure-release, and air-bleed modes of operation of the solenoid valve assembly characterised in that , in said assembly (10), the tubular guide means comprises first and second tubular guides (62,64); there are oppositely-extending first and second plunger springs (72,74) respectively urging said first and second plungers (79,90) axially away from said stop element (60); there is a plate (28) received by the stop element (60) between the tubular guides (62,64) to anchor and locate the plunger stop assembly (58) axially and radially within said housing (12,20); and said second plunger (90) has a passage (92) therethrough providing said fluid communication with said stop element axial passage (66) to said valve element (94). A solenoid valve assembly according to claim 1, characterised in that said first valve housing (42) further has a non-spring-biased check valve (160) therein between said pressure inlet (148) and said pressure outlet (126) and acted on by pressures therein to open when pressure in said pressure outlet (126) exceeds the pressure in said pressure inlet (148) to limit the pressure in said pressure outlet (126) to the pressure in said pressure inlet (148), and to be closed whenever the pressure in said pressure inlet (148) exceeds the pressure in said pressure outlet (126). A solenoid valve assembly according to claim 1, characterised in that said first valve housing (42) contains a triple cascade orifice arrangement intermediate said pressure inlet (148) and said pressure outlet (126) defined by a thin plate first orifice (140), a restrictive flow passageway second orifice (150), and a ball valve (88) retained within a tapered valve seat (152) which is at least a part of said valve means, the opening of said ball valve (88) in said tapered valve seat (152) providing a restrictive flow third orifice (156), said triple cascade orifice arrangement providing sufficient fluid flow at high fluid pressures at said pressure inlet (148) and stepped pressure differentials across each of said first and second and third orifices (140,150,156), substantially eliminating fluid cavitation and alleviating induced noises resulting therefrom. A solenoid valve assembly according to claim 1, characterised in that the first and second solenoids (16,18) comprise first and second oppositely wound, axially-aligned, selectively electrically energizable and de-energizable solenoid coils (34,36) having their adjacent ends in juxtaposed relationship to one another; said first and second plungers (79,90) are first and second coaxially-positioned solenoid armature plungers (79,90) respectively received within said first and second solenoid coils (34,36); said first valve housing (42) and a second valve housing (48) housing said normally-closed second valve means (96) are positioned in axial alignment with said plungers (79,90) outside of but adjacent to the opposite ends of said solenoid coils (34,36) and respectively have said first and said second valves (88,96) therein; said pressure inlet (148) is in fluid communication with said first valve (88) on the inlet side thereof and said pressure outlet (126) is in fluid communication with said first valve (88) on the outlet side thereof; said second valve (96) has the inlet side thereof in continuous fluid communication with the outlet side of said first valve (88); and said pressure exhaust port (110) is in continuous fluid communication with the outlet side of said second valve (96); said assembly being adapted to operate in a first, pressure-apply, mode with both solenoid coils (34,36) de-energized and said first valve (88) open and said second valve (96) closed to conduct pressurized hydraulic fluid from said pressure inlet (148) to said pressure outlet (126) when that pressure outlet (126) is connected to a hydraulic fluid pressure-operated means; said assembly being adapted to operate in a second, pressure-hold, mode with said first solenoid coil (34) electrically energized and said second solenoid coil (36) de-energized and both of said first and second valves (88,96) closed to hold hydraulic fluid pressure in said pressure outlet (126) at the pressure present therein when said first valve (88) closed; said assembly being adapted to operate in a third, pressure-release, mode with both of said solenoid coils (34,36) electrically energized and said first valve (88) closed and said second valve (96) open to release hydraulic fluid pressure from said pressure outlet (126); and said assembly being adapted to operate in a fourth, air-bleed, mode with said first solenoid coil (34) de-energized and said second solenoid coil (36) electrically energized and both of said first and second valves (88,96) open to bleed air from said assembly (10) and from said pressure inlet (148) and outlet (126) and thus being adapted to also bleed air from hydraulic fluid present in any hydraulic devices which may be secured to said pressure inlet (148) and pressure outlet (126). A solenoid valve assembly according to claim 4, characterised in that the direction of coil windings in said solenoid coils (34,36) and the direction of electrical current flowing through one of said solenoid coils (34,36) when only the one of said solenoid coils (34,36) is electrically energized is such that any magnetic field of said one electrically energized solenoid coil which influences the armature plunger of the other of said solenoid coils acts on that armature plunger to urge it in the axial direction opposite to the axial direction in which that armature plunger is magnetically urged by the other of said solenoid coils when said other solenoid coil is electrically energized. A solenoid valve assembly according to claim 4, characterised in that the direction of coil windings in said solenoid coils (34,36) and the direction of electrical currents flowing therethrough when both of said solenoid coils (34,36) are electrically energized are such that the magnetic flux patterns thereof generated at their adjacent ends enhance each other.

Inventors: PARROTT, RICHARD M., PENG, YUCHI P., RICKETTS, WILLIAM J.
Applicants: GENERAL MOTORS CORPORATION
Application year: 1988
Main classification: B60T8
IPC codes: B60T8