Abstract:
Relatively simple partially or completely pressure balanced valves are disclosed having relatively low friction and gas forces to be overcome by a solenoid actuator. Various devices are provided for sealing of the valve members to maintain low leakage of gases through the valve or into the actuator. Movable members of the valve and actuator are engaged but physically separate so they may be separately replaced. Various actuators may by applied with various valve assemblies for flexibility in meeting the requirements of alternative applications.

Description:
TECHNICAL FIELD 
     This invention relates to gas valves. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to vehicle engines to provide selective recirculation of engine exhaust gases into the intake manifold under certain operating conditions in order to maintain controlled exhaust emissions within desired limits. For controlling such exhaust gas recirculation, an EGR valve may be provided which includes a valve assembly mountable or connectable to associated intake and exhaust manifolds or systems of the engine to meter the flow of exhaust gas from the intake to the exhaust. 
     The EGR valve may include a valve assembly operable to close or open a passage between the intake and exhaust manifolds. An actuator assembly may be mounted on or connected with the valve assembly and include a solenoid coil and an armature actuated by the coil to open the EGR valve, which is closed by a spring when the coil is deenergized. Pressure differentials between the intake and exhaust of naturally aspirated engines with manifold fuel injection require substantial solenoid energy to open the valve. With potential application to other engines, such as turbocharged engines, direct injection gasoline engines and diesel engines, where even larger gas flows may be required, reduction of solenoid energy for valve opening is desired to allow use of available solenoid actuators with valves for various engine applications. In addition, it is desirable to reduce or eliminate the effects of intake or exhaust pressure pulsations on the armature, solenoid and closing spring mass system to improve positional stability. 
     SUMMARY OF THE INVENTION 
     The present invention provides relatively simple partially or completely pressure balanced exhaust gas recirculation (EGR) valves having relatively low friction and gas forces to be overcome by the actuator. Pressure balancing reduces the solenoid and spring energy needed to actuate the valves and balances out the effects of intake or exhaust pressure pulsations on the armature, solenoid, and closing spring mass system. Various means are provided for sealing of the valve members to maintain low leakage of gases through the valve or into the actuator. The valve and actuator may be mounted together for drop in installation into an engine assembly or they may be separately mounted for use in various engine installations. Movable members of the valve and actuator are engaged but physically separate so they may be separately replaced. Various actuators may by applied with various valve assemblies for flexibility in meeting the requirements of a alternative engine applications. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a cross-sectional view of a first embodiment of a partially balanced valve according to the invention as applied as an EGR valve in an engine; 
     FIG. 2 is a view similar to FIG. 1 showing a second embodiment of an EGR valve mounted in an attached base; 
     FIG. 3 is a fragmentary cross-sectional view of a third embodiment with full balancing and modified seals; 
     FIG. 4 is a fragmentary cross-sectional view of a fourth embodiment modified from that of FIG. 3 
     FIG. 5 is a cross-sectional view of a fifth embodiment with a specific seal arrangement; 
     FIG. 6 is a cross-sectional view similar to FIG. 5 of a sixth embodiment with an alternative seal arrangement; 
     FIG. 7 is a cross-sectional view similar to FIGS. 5 and 6 of a seventh embodiment with another seal arrangement; 
     FIG. 8 is a cross-sectional view similar to FIG. 5 but showing an alternative piston arrangement; and 
     FIG. 9 is a cross-sectional view similar to FIGS. 5-7 but including various alternative features. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 of the drawings in detail, numeral  10  generally indicates an internal combustion engine having an exhaust manifold  12  or other exhaust gas carrying component. Manifold  12  includes a cylindrical mounting recess  14  connecting through an inlet opening  16  at one end with an exhaust gas passage  18  in the manifold  12 . An outlet port  20  in the side of the recess  14  connects with an associated intake manifold, not shown, or another portion of an engine induction system. The recess  14  is open to a generally planar surface  22  of the manifold  12  with an annular counterbore  24  surrounding the opening. A coolant passage  26  in the manifold extends adjacent the recess  14  below the surface  22 . 
     Mounted on the manifold  12  is a first embodiment of exhaust gas recirculation (EGR) valve  28  according to the invention. EGR valve  28  includes a solenoid actuator  30  mounted on the manifold surface  22  by fasteners, such as screws  31 , and a valve assembly  32  associated with the actuator and mounted in the manifold recess  14 . Actuator  30  includes a housing  34  enclosing a solenoid coil  36  and including upper and lower magnetic poles  38 ,  40  in which a hollow cylindrical armature  42  is reciprocably movable. A nonmagnetic sheath  44  surrounds the armature and provides a low friction surface on which the armature is slidable. A spring  46  biases the armature upwardly and seats against the sheath  44  near a bottom  48  of the housing seated on the upper surface  22  of the exhaust manifold  12 . 
     The valve assembly  32  includes a valve body in the form of a generally cylindrical seat tube  50  having an upper end received within a flange  52  on the bottom  48  of the housing and extending into the counterbore  24  of the exhaust manifold. The seat tube  50  extends downward into the mounting recess  14  of the exhaust manifold and engages a seal ring  54  seated on a flange defining the inlet opening  16  into the mounting recess  14 . The lower end of the seat tube  50  defines an annular valve seat  56  with which the head  58  of a valve member or pintle  60  is engagable. The pintle  60  also has a shaft or stem  62  which extends upward through the seat tube, spring and armature to engagement with a linear position sensor drive arm  64 . Means, such as a spring seat and cap  66  crimped onto the stem  62 , removably engages and connects the pintle with the spring  46  and the armature  42 , allowing the spring to bias the armature and pintle upwardly to seat the head  58  and close the valve. The seat tube  50  has a hollow interior which defines, in part, a passage  68  connecting the valve seat  56  with a side opening  70  communicating with the outlet port  20  of the exhaust manifold. 
     The pintle or valve member  60  further includes a balance piston  72  axially spaced from the valve head  58  above the side opening  70  and having an axially projected area approximately equal to that of the valve head  58  when it is seated. Piston  72  is slidable within and sealingly engages an internal cylinder  74  of a pintle shaft bushing  76 . Bushing  76  includes an annular flange  78  which is biased by a spring  80  into sealing engagement with a planar annular surface  82  of the seat tube  50 . The bushing  76  is self-aligned laterally on the surface  82 , so that alignment of the piston  72  with the cylinder  74  is inherent and the valve head  58  is allowed to center itself in the valve seat  56 . Thus, good sealing contact of the valve head and seat as well as the piston and cylinder are maintained. 
     In operation, the solenoid actuator  30  is connected to an outside controller or power source, not shown, in order to energize the coil  36  and open the valve  32 . The power source may have a constant voltage for full opening or closing of the valve or the power may be modulated in order to vary the valve opening in accordance with desired operating parameters. 
     When the valve is closed, valve head  58  engages valve seat  56 , blocking exhaust gas flow from the manifold passage  18  into the valve body formed by the seat tube  50 . During this time, variations in intake manifold pressure acting in the passage  68  within the seat tube  50 , are balanced by the relatively equal axially projected areas of the valve head  58  and piston  72  on which the varying pressures act. When the solenoid coil  36  is energized, the armature  42  is actuated downwardly against the bias of spring  46 , opening the valve and allowing exhaust gas to flow from the manifold passage  18  through the inlet opening  16  into the transfer passage  68  and out the side opening  70  to the manifold outlet port  20  which connects with the engine intake manifold, not shown. 
     The close fitting of the piston  72  within the cylinder  74  and the floating seal provided by engagement of the pintle shaft bushing flange  78  against the annular surface  82  of the seat tube, which is maintained by the force of the spring  80 , minimizes the leakage of gases between the passage  68  and the exterior of the valve. A vent passage  84  is provided in the lower portion of the solenoid housing  34  to relieve any gas pressure which might otherwise develop in this location and prevent the escape of exhaust gas into the solenoid housing. The coolant passage  26  in the exhaust manifold is positioned to protect the solenoid actuator mounted on the manifold from the high exhaust gas temperatures passing through the valve assembly  32  of the EGR valve. 
     FIG. 2 of the drawings illustrates a second embodiment of EGR valve according to the invention which is generally indicated by numeral  90 . In general, valve  90  operates in much the same manner as the valve  28  previously described and, where appropriate, like numerals indicate similar parts as to which further description is thought to be unnecessary. There are, however, a number of differences in construction which are described below. 
     In valve  90 , the valve body  92  is formed as a base having a mounting face  94  that is attachable against an associated surface of an internal combustion engine, not shown. Alternatively, the valve body could be part of a manifold or other component of the engine as in the embodiment of FIG.  1 . The valve body  92  includes dual passages  96 ,  98  which extend through the base or body  94  and are connectable with associated passages in the induction system and exhaust system of the associated engine. Internally, passages  96 ,  98  are joined through a pressed in and staked valve seat  100  which defines an orifice connecting the two passages whenever the valve is open. Varying induction system pressures which exist in passage  96  act, as in EGR valve  28 , upon approximately equal axially projected areas of the head  58  and piston  72  of valve member  60  so as to balance out the effect of varying induction system pressures in the same manner as in valve  28 . 
     The piston  72  is movable within a floating bushing  76 , as before, however, the bushing is urged downward by a wave spring  102  instead of the coil spring of valve  28 . The flange  78  is slidable on an annular surface  82  of the valve body to seal against leakage around the exterior of the bushing. A thin walled gas shield  104  is applied between the valve body  92  and solenoid actuator  106  to minimize the escape of exhaust gases into the solenoid actuator. Vents  108 ,  109 , located above and below the gas shield, communicate the opposite sides of the gas shield separately with atmosphere and, thus, minimize the transfer of gases between the actuator and the valve body. The diameter of the pintle shaft  62  as it passes through the floating bushing  76  is sized to provide a clearance  110  between the bushing and the shaft  62 . This allows communication of ambient pressures to the upper side of the balance piston  72  for balancing the forces and opposing the leakage of exhaust gases past the piston. 
     A coolant passage  26  is provided in the valve body to limit the transfer of exhaust gas temperatures to the solenoid actuator, as before. The actuator  106  is mounted to the valve body  92  as by screws  31  to form the complete EGR valve ready for mounting on an associated engine. 
     FIG. 3 illustrates a third embodiment of EGR valve  116  which represents the first of several embodiments to be described which are suitable for use in diesel or gasoline direct injection engines, where both exhaust and intake manifold pressures may significantly vary. 
     In these embodiments, both intake and exhaust system pressures are approximately balanced on the valve so that variations in either one will have little effect on the opening and closing forces required to actuate the valve. In addition, the direction of exhaust gas flow can be reversed so that he exhaust gas flows from a side port into a central chamber and then, when the valve is open, out past the valve head to the intake manifold or engine induction system which is connected to a lower opening or orifice of the valve that is controlled by a valve head. The valve can also be operated with a gas flow direction as described with respect to FIGS. 1 and 2. 
     EGR valve  116  is exemplary in that the pintle or valve member  118  has a stem or shaft  120  which includes a hollow or tubular lower portion  122  attached to a solid upper portion  124 . A head  126  is mounted on the lower end of the tubular portion while a balance piston  128  is mounted near the upper end of the tubular portion. The balance piston is retained axially by staking the tubular portion  122  where it interfaces the balance piston  128 . The valve head  126  engages a valve seat  130 , formed at the lower end of a seat tube  132  which forms the valve housing or valve body. 
     Exhaust gas enters through a side opening  134  in the seat tube into a transfer chamber  136  where exhaust system pressures are exerted in opposite directions on the approximately equal axially projected areas of the valve head and the piston, thereby balancing exhaust pressures in the same manner as the intake or induction system pressures were balanced in the previous embodiments. Induction system pressures are also balanced, in that intake pressure acting on the lower surface of the valve head  126  is also conducted through the tubular lower portion  122  of the shaft through an opening  138  to a balance chamber  140  located above the balance piston  128  and below a floating shaft seal  142 . Thus, intake pressures are exerted on the outer ends of the valve head and piston leading to approximate balancing of the intake forces on the valve. 
     The floating shaft seal  142  engages outwardly the upper end of a floating bushing  144  which defines a cylinder in which the piston  128  reciprocates. Bushing  144  also includes a flange  145  which engages a planar annular surface  146  of the seat tube or valve housing  132 . Thus, gas pressures within the intake and exhaust gas exposed chambers are sealed to minimize leakage from these chambers. A wave spring  102  is provided to maintain sealing pressure on the floating shaft seal  142  and floating bushing  144 . A seal  148 , such as GARPHOIL or TEFLON, engages the shaft  120  to block gas leakage into the actuator and direct it out a vent  149 . Piston  128  can be allowed to float radially or rock slightly on the tubular portion  122  of shaft  120  which allows the piston to be self aligned with the inner cylinder surface of the floating bushing  144 . It may also enhance alignment of the pintle valve head  126  and seat  130 . This floating piston feature may also be applied in all of the balance pistons subsequently discussed. 
     FIG. 4 discloses a fourth embodiment of EGR valve  150  which represents a modification of the embodiment of FIG.  3 . In valve  150 , an optional lip seal  152  is provided that engages an upper end of the balance piston  154  to more positively seal against leakage between intake and exhaust portions when the valve is closed. In other respects, valve  150  in FIG. 4 is similar to valve  116  in FIG. 3, wherein like numerals indicate like or similar parts. 
     Referring now to FIGS. 5-7, there are shown three additional embodiments of EGR valves  160 ,  162  and  164 . These valves are similar in that they each include a solenoid actuator  106  which bolts directly onto an engine component in which a valve assembly is received. 
     EGR valve  160 , shown in FIG. 5, has a valve assembly  165  that includes a seat tube  166  forming the valve body. A valve member  168  is received in the seat tube and includes a formed tubular lower portion  170  which holds together a separate head  172 , tubular shaft  174  and balance piston  176 . The piston  176  reciprocates in a cylinder  177  formed by an inner surface of the seat tube  166 . The balance piston  176  is hollow and open at an upper end. In the closed position of the valve  160 , an annular upper edge of the piston  176  engages a lip seal  178  which prevents gas transfer between the intake and exhaust systems through the valve when the valve is closed. The lip seal  178  is carried by a floating shaft seal  179  having a flange  180  which is urged downwardly against a sealing surface  181 , as before, by a wave spring  102  seated against a gas shield  182 . A floating actuator seal  183  is seated on the shaft seal  179  and surrounds the shaft upper portion  124  to limit the passage of gases up into the solenoid actuator  106 . Vents  184 ,  185  are provided above and below the gas shield  182  to minimize gas transmission between the valve body or seat tube  166  and the solenoid actuator  106 . 
     EGR valve  162 , shown in FIG. 6, is generally similar to valve  160  but the valve assembly  186  differs in details of the seat tube  187  which carries a radial piston seal  188  that engages an outer surface of the balance piston  176  when the valve is closed. The radial piston seal  188  is also engaged by the lower edge of a modified floating shaft seal  190  which is urged downwardly by the wave spring  102 , as before. The construction is otherwise similar to that of valve  160 . 
     EGR valve  164 , shown in FIG. 7, is again similar to valves  160  and  162  but the valve assembly  191  differs in the modified form of the seat tube  192  which carries a floating face and radial piston seal  194 . Seal  194  is biased by a spring  196  against the upper end of the balance piston  176  when the valve is closed. The spring  196  acts between the seal  194  and a modified floating shaft seal  198 . Seal  194  also radially contacts a cylinder surface within the seat tube  192 , thus preventing gas leakage either along the cylinder wall or past the end of the piston when the valve is closed. The axial travel of the seal  194  and its engagement with the balance piston  176  is controlled by a step  200  in the seat tube  192 . The step  200  limits downward motion so the seal  194  is engaged by the balance piston for only a short distance near the top of its travel near and in the valve closed position. In other respects, the embodiment of valve  164  is similar to valves  160  and  162 , previously described. 
     FIG. 8 illustrates an EGR valve  201  having a valve assembly  202  similar to assembly  165  of FIG.  5 . In valve assembly  202 , a balance piston  204  is modified to include external grooves  206 . The groove edges scrape off any carbon build up from the cylinder  177  of the seat tube  166  and thus minimize frictional changes that might otherwise occur over time in the valve operation. 
     FIG. 9 shows another EGR valve  210  similar to those of FIGS. 3-8 but having certain modified features. A solenoid actuator  212  is provided having internal structure generally like those of the previously described embodiments. However, the housing  214  is modified to include a separate base plate  216  which is attached to the lower magnetic pole  218  by rivets  220 . The base plate  216  is then attached to the associated valve body, manifold or other engine component  222  by screws  31  in a conventional manner. 
     The valve assembly  224  includes a seat tube  226  having a cylinder with internal grooves  228  that scrape off carbon buildup as do the piston grooves  206  of FIG.  9 . The upper end of the seat tube  226  is radially enlarged with a cylindrical flange  230  that is received in circular recesses  232 ,  234  of the engine component  222  and the actuator base plate  216  respectively. A large floating bushing  236  is mounted on the solid upper portion of the pintle shaft  237  and is urged against an annular surface of the seat tube by a wave spring  102  to seal against exhaust gas leakage as before. The pintle shaft  237  is one piece with the solid and hollow portions formed integrally. At the lower end, the seat tube  226  has a seat ring  238  that engages a separate valve seat  240  to hold it in place in a counterbore  242  of the engine component  222 . 
     In all of the previously described embodiments, the valve member or pintle is in contact with, but not attached to, the armature in the solenoid actuator. Thus, with appropriate component design, a solenoid actuator may be replaced without disturbing the valve assembly of any of the EGR valves illustrated. Further, this feature allows interchange of varying forms of actuators with various arrangements of valve assemblies to provide numerous variations in the EGR valves with a minimum of differing component parts. 
     While the invention has been described by reference to EGR applications and certain preferred embodiments thereof, it should be understood that numerous other applications and changes could be made within the spirit and scope of the inventive concepts described. Accordingly it is intended that the invention not be limited to the disclosed EGR application or embodiments, but that it have the full scope permitted by the language of the following claims.