EXHAUST GAS RECIRCULATION VALVE ASSEMBLY

Abstract: A valve assembly (l0) for controlling recirculation of exhaust gases has three solenoid-operated valve members (32) that meter flow of exhaust gases through calibrated outlets (20a) from an exhaust gas chamber (l8). Each valve member (32) has a valve stem (30) extending to a respective solenoid armature (28), and each valve stem (30) is surrounded by a pair of spring-biased seals (34,36) that seal openings (44,50) around the valve stem (30) into a respective solenoid coil (24) and the chamber (l8). In this assembly (l0), each armature-valve member-seal (28,32,34,36) floats laterally to compensate for potential misalignment between the respective solenoid coil (24) and the respective outlet (20a).

Description: Technical Field This invention relates to a valve assembly for controlling recirculation of exhaust gases in an internal combustion engine. Background and summary of the invention When employing an electrically-actuated valve assembly to control exhaust gas recirculation, the actuator should be isolated from the exhaust gases to assure proper operation. Electrically-actuated valve assemblies heretofore proposed for controlling exhaust gas recirculation have not isolated the actuator from the exhaust gases in a practical manner. This invention provides a practical electrically-actuated exhaust gas recirculation valve assembly in which the actuator is isolated from the exhaust gases to assure proper operation. In a preferred embodiment of an exhaust gas recirculation valve assembly employing this invention, a valve member controls the flow of exhaust gases from an exhaust gas chamber through a calibrated valve seat. A solenoid coil is located outside the chamber, and the valve member has a valve stem extending to a solenoid armature surrounded by the coil. The valve stem is surrounded by a pair of spring-biased seals that seal the openings around the valve stem into the solenoid coil and the chamber, and the armature-valve member-seal sub-assembly floats laterally to compensate for potential misalignment between the solenoid coil and the outlet. The details as well as other features and advantages of three embodiments of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings. Summary of the drawings Figure l is a sectional view of a first embodiment of an exhaust gas recirculation valve assembly incorporating this invention. Figure 2 is a bottom view of the Figure l embodiment, showing calibrated outlets thereof. Figure 3 is an enlarged view of a armature-valve member-seal sub-assembly employed in Figure l embodiment. Figure 4 is a partially sectional view of a second embodiment of an exhaust gas recirculation valve assembly incorporating this invention. Figure 5 is a partially sectional view of a third embodiment of an exhaust gas recirculation valve assembly incorporating this invention. Figure 6 is a plan view of the Figure 5 embodiment. The preferred embodiments Referring first to Figures l-3, an exhaust gas recirculation valve assembly l0 includes a base l2 having an inlet l4 for receiving exhaust gas from the engine. A cover l6 overlies base l2 to enclose an exhaust gas chamber l8, and base l2 has three calibrated outlets 20a, 20b, 20c each surrounded by a valve seat 22. A solenoid coil 24 is mounted on a bracket 26 over each valve seat 22. Each coil 24 surrounds an armature 28, and a valve stem 30 extends from each armature 28 to a valve member 32 disposed in chamber l8. A pair of seals 34 and 36 surround each valve stem 30. Each upper, or bracket seal 34 has a central disk portion 38 embracing valve stem 30 and a peripheral lip 40 biased by a spring 42 to engage bracket 26. Bracket seals 34 seal the openings 44 through bracket 26 about valve stems 30 and armatures 28. Each lower, cover seal 36 has a hub 46 embracing valve stem 30 and a peripheral flange portion 48 biased by spring 42 to engage cover l6. Cover seals 36 seal the openings 50 through cover l6 about valve stems 30. Seals 34 and 36 are formed of sintered graphite bronze, stainless steel, or other material selected to provide the desired lubricity and wear resistance. The bore 52 through the hub 46 of lower seal 36 may be chamfered at top and bottom to allow valve stem 30 to slide easily through seal 36. Chamfers are not required on the bore 54 through the thin central disk portion 38 of upper seal 34. To construct valve assembly l0, three solenoid coils 24 are secured on bracket 26 and the coil-bracket sub-assembly is inverted. Three armature-valve member-seal sub-assemblies 55 are made by placing lower seal 36, spring 42 and upper seal 34 on valve stem 30, placing armature 28 on valve stem 30, and upsetting tip 56 of valve stem 30 to secure the armature-valve member-seal sub-assembly. Springs 57 are inserted in each solenoid coil 24, and armatures 28 are then inserted through bracket openings 44 into solenoid coils 24. Cover l6 is secured to base l2 by fasteners 58, and the cover-base sub-assembly is inverted, assembled with valve members 32 extending through openings 50 to engage valve seats 22, and secured to bracket 26 with fasteners 60. Springs 42 react between the central disk portion 38 of upper seal 34 and the peripheral flange portion 48 of lower seal 36 to engage seal 34 with bracket 26 and seal 36 with cover l6. In operation, each spring 57 biases the respective armature 28 and valve stem 30 to engage the respective valve member 32 with the associated valve seat 22. When a solenoid coil 24 is energized, the respective armature 28 and valve stem 30 are lifted against the bias of the respective spring 57 and the respective valve member 32 is raised away from the associated valve seat 22 to allow recirculation of exhaust gases. Preferably, the areas of outlets 20a, 20b, 20c are calibrated as a binary series with the area of outlet 20b twice that of outlet 20a and the area of outlet 20c twice that of outlet 20b; in some applications, however, other combinations of outlet areas may be used. Recirculation of exhaust gases is metered by energizing the appropriate solenoid coil or coils 24 to raise the appropriate valve member or members 32 away from the associated valve seat or seats 22 and thus allow recirculation of exhaust gases through one or more of the calibrated outlets 20a, 20b, 20c. Each solenoid coil 24 has a pole piece 62 threaded into a yoke 64. Adjustment of pole piece 62 in yoke 64 determines the preload that the associated spring 57 exerts on the corresponding armature-valve stem-valve member, the air gap between the corresponding armature 20 and the respective pole piece 62 when the corresponding coil 24 is not energized, and the travel of the corresponding armature-valve stem-valve member when the corresponding coil 24 is energized. Although the assembly l0 is shown here as having a circular base l2, it is clear that other configurations could be adopted within the space limitations of the particular engine application. Referring now to Figure 4, an exhaust gas recirculation valve assembly ll0 includes a base ll2 having an inlet ll4 for receiving exhaust gas from the engine. A cover ll6 overlies base ll2 to enclose an exhaust gas chamber ll8, and base ll2 has three calibrated outlets l20 (only one being shown) each surrounded by a valve seat l22. A solenoid coil l24 is mounted on a bracket l26 over each valve seat l22. Each coil l24 surrounds an armature l28, and a valve stem l30 extends from each armature l28 to a valve member l32 disposed in chamber ll8. A pair of seals l34 and l36 surround each valve stem l30. Each upper, bracket seal l34 embraces valve stem l30 and is biased by a spring l42 to engage bracket l26. Bracket seals l34 seal openings l44 through bracket l26 about valve stems l30 and armatures l28. Each lower, cover seal l36 has a hub l46 embracing valve stem l30 and a peripheral flange portion l48 biased by spring l42 to engage cover ll6. Cover seals l36 seal openings l50 through cover ll6 about valve stems l30. Seals l34 and l36 are formed of sintered graphite bronze, stainless steel, or other material selected to provide the desired lubricity and wear resistance. The base ll2 of assembly ll0 has a discharge chamber l37 to route exhaust gases metered through outlets l20 to a common discharge opening l39. The embodiment shown in Figure 4 is assembled, adjusted and operated in the manner described above for the embodiment shown in Figures l-3. Referring next to Figures 5-6, an exhaust gas recirculation valve assembly 2l0 includes a base 2l2 having an inlet 2l4 for receiving exhaust gas from the engine. A cover 2l6 overlies base 2l2 to enclose an exhaust gas chamber 2l8, and base 2l2 has three calibrated outlets 220 (only one being shown) each surrounded by a valve seat 222. A solenoid coil 224 is mounted on a bracket 226 over each valve seat 222. Each coil 224 surrounds an armature 228, and a valve stem 230 extends from each armature 228 to a valve member 232 disposed in chamber 2l8. A pair of seals 234 and 236 surround each valve stem 230. Each upper, bracket seal 234 has a central disk portion 238 embracing valve stem 230 and a peripheral lip 240 biased by a spring 242 to engage bracket 226. Bracket seals 234 seal openings 244 through bracket 226 about valve stems 230 and armatures 228. Each lower, cover seal 236 has a central disk portion 246 embracing valve stem 230 and a peripheral rim 248 biased by spring 242 to engage cover 2l6. Cover seals 236 seal openings 250 through cover 2l6 about valve stems 230. Seals 234 and 236 are formed of a material such as sintered graphite bronze selected to provide the desired lubricity and wear resistance. In addition, the central disk portion 246 of lower seal 236 scrapes valve stem 230 to prevent any accumulation of deposits on stem 230. To construct valve assembly 2l0, three solenoid coils 224 are secured on brackets 226, and three armature-valve member-seal sub-assemblies 255 are made by placing valve member 232, lower seal 236, spring seat 255a and return spring 255b, seal spring 242 and upper seal 234 on valve stem 230, placing armature 228 on valve stem 230, and upsetting tip 256 of valve stem 230 to secure the armature-valve member-seal sub-assembly. Armatures 228 are then inserted through bracket openings 244 into solenoid coils 224, the cover 2l6 and base 2l2 is assembled with valve members 232 extending through openings 250 to engage valve seats 222, and fasteners 260 are inserted through bracket 226 and cover 2l6 and threaded into base 2l2. Springs 242 react between the central disk portion 238 of upper seal 234 and the central disk portion 248 of lower seal 236 to engage seal 234 with bracket 226 and seal 236 with cover 2l6. In operation, each spring 255b biases the respective armature 228 and valve stem 230 to engage the corresponding valve member 232 with the associated valve seat 222. When a solenoid coil 224 is energized, the respective armature 228 and valve stem 230 are lifted against the bias of the corresponding spring 255b and the corresponding valve member 232 is raised away from the associated valve seat 222 to allow recirculation of exhaust gases. Each solenoid coil 224 has a pole piece 262 threaded into a yoke 264. Adjustment of pole piece 262 in yoke 264 determines the air gap and travel of the corresponding of its armature-valve stem-valve member. After adjusting pole piece 262 in yoke 264, yoke 264 is crimped laterally to prevent changes in the adjustment. Each valve member 232 swivels on a ball 266 formed at the end of the corresponding valve stem 230 to assure proper alignment of the valve member 232 on the corresponding valve seat 222. It will be noted that each orifice 220 has the narrowest opening at the top and a wider region 268 below. With this construction, any deposits that tend to accumulate in the orifice 220 would be pushed by the valve member 232 in the direction of flow through the orifice 220 into the wider region 268, thereby reducing the potential for any plugging of orifice 220. It will be appreciated that exhaust gas recirculation also could be metered with these assemblies by operating one or more solenoids as linear solenoids that vary the extent to which the respective valve member may be lifted away from the corresponding valve seat and thus vary the flow area between the valve member and the corresponding valve seat. Moreover, one or more solenoids could be operated as pulse width-modulated or frequency-modulated solenoids that vary the time during which the respective valve member is lifted away from the corresponding valve seat and thus vary the flow past the valve member. In each embodiment, moreover, it will be appreciated that a solenoid coil 24, l24, 224 might not be precisely aligned over a valve seat 22, l22, 222. With this invention, however, the valve stem 30, l30, 230 is not constrained by a fixed seal in the cover opening 50, l50, 250. Instead, the armature-valve member-seal sub-assemblies 55, l55, 255 float laterally to compensate for potential misalignment of the solenoid coils 24, l24, 224 while still assuring that bracket openings 44, l44, 244 and cover openings 50, l50, 250 are sealed. It will be noted that the central disk portions 246 of lower or cover seals 236 are slightly convex to assist in centering within openings 250 during assembly but still allow seals 236 to float laterally as indicated above.

Claims: 1. An exhaust gas recirculation valve Assembly (l0; ll0; 2l0) including a base (l2; ll2; 2l2) having an exhaust gas chamber (l8; ll8; 2l8), an inlet opening (l4; ll4; 2l4) to said chamber, an outlet opening (20a,20b,20c; l20; 220) from said chamber, and a valve seat (22; l22; 222) surrounding said inlet or said outlet, said base (l2; ll2; 2l2) including a cover (l6; ll6; 2l6) closing said chamber (l8; ll8; 2l8), said cover (l6; ll6; 2l6) having an opening (50; l50; 250) generally aligned with said valve seat (22; l22; 222), a valve stem (30; l30; 230) extending through said opening (50; l50; 250), a valve member (32; l32; 232) mounted adjacent said valve seat (22; l22; 222) at one end of said valve stem (30; l30; 230), and an actuator (24; l24; 224) at the other end of said valve stem (30; l30; 230), said actuator (24; l24; 224) being energizable for operating said valve stem (30; l30; 230) to reciprocate said valve member (32; l32; 232) into and out of engagement with said valve seat (22; l22; 222), characterised in that said assembly (l0; ll0; 2l0) further comprises a movable seal (36; l36; 236) surrounding said valve stem (30; l30; 230) outside said chamber (l8; ll8; 2l8), and a spring (42; l42; 242) surrounding said valve stem (30; l30; 230) which biases said movable seal (36; l36; 236) into engagement with said cover (l6; ll6; 2l6) to seal said cover opening (50; l50; 250). 2. An exhaust gas recirculation valve assembly according to claim l, characterised in that the valve member (32; l32; 232) is mounted in said chamber (l8; ll8; 2l8) at one end of said valve stem (30; l30; 230), there is a solenoid armature (28; l28; 228) mounted at the other end of said valve stem (30; l30; 230), and there is a solenoid coil (24; l24; 224) surrounding said armature (28; l28; 228), which is energizable to move said valve stem (30; l30; 230) so as to reciprocate said valve member (32; l32; 232) into and out of engagement with said valve seat (22; l22; 222). 3. An exhaust gas recirculation valve assembly according to claim 2, characterised in that there is a bracket (26; l26; 226) supporting said solenoid coil (24,l24,224) on said base (l2; ll2; 2l2), said bracket (26; l26; 226) having an opening (44; l44; 244) generally aligned with said cover opening (50; l50; 250), said valve stem (30; l30; 230) extends through said bracket opening (44; l44; 244), and there is a movable bracket seal (34; l34; 234) surrounding said valve stem (30; l30; 230) between said bracket (26; l26; 236) and said cover (l6; ll6; 2l6), which movable bracket seal (34; l34; 234) is biased into engagement with said bracket (26; l26; 226) by said spring (42; l42; 242) to seal said bracket opening (44; l44; 244).

Inventors: FORNUTO, JOSEPH, WENDT, PETER RONALD
Applicants: GENERAL MOTORS CORPORATION
Application year: 1987
Main classification: F02M25
IPC codes: F02M25