Patent Publication Number: US-6209529-B1

Title: Injector EGR valve and system

Description:
This application is a continuation of U.S. Ser. No. 09/107,514, filed on Jun. 30, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to exhaust gas recirculation (EGR) valves and systems for automotive vehicle internal combustion engines. 
     BACKGROUND OF THE INVENTION 
     Controlled engine exhaust gas recirculation is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A typical EGR system comprises an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the fuel-air flow entering the engine for combustion so as to limit the peak combustion temperature and hence reduce the formation of oxides of nitrogen. 
     Exhaust emission requirements have been imposing increasingly stringent demands on tailpipe emissions that may be met by improved control of EGR valves. An electromagnetically operated actuator controlled by an engine management computer is one device for obtaining improved EGR valve control. It is known to associate such a valve with an engine intake manifold to dope the induction flow before the flow passes to runners to each individual cylinders. 
     It is also known to provide each cylinder with a strictly mechanical mechanism to recirculate exhaust gas from a cylinder back to the intake of the cylinder. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention relates to an internal combustion engine having multiple combustion chambers each having intake and exhaust valves for controlling intake and exhaust flows into and from the combustion chamber, an induction system to the intake valves, an exhaust system from the exhaust valves, and an EGR system for controlling recirculation of exhaust flow to the combustion chambers comprising an individual electric-actuated EGR valve associated with each respective combustion chamber for controlling the exhaust recirculation to the respective combustion chamber independent of the exhaust gas recirculated to any other combustion chamber. 
     Another aspect of the present invention relates to an internal combustion engine having multiple combustion chambers, an exhaust system through which exhaust gas is conducted from the combustion chambers, and an exhaust gas recirculation rail assembly mounted on the engine, the exhaust gas recirculation rail assembly comprising an exhaust gas recirculation rail forming an exhaust gas recirculation manifold communicated to the exhaust system, plural electric-actuated EGR valves mounted on the rail, each comprising its own inlet port communicated to the exhaust gas recirculation manifold and its own outlet port for recirculation of exhaust gas from the exhaust system to a respective combustion chamber such that recirculation of exhaust gas through each valve is controlled independent of the exhaust gas recirculated through the other valves. 
     Still another aspect of the present invention relates to a method of exhaust gas recirculation in an internal combustion engine having multiple combustion chambers each having intake and exhaust valves for controlling intake and exhaust flows into and from the combustion chamber, an induction system to the intake valves, an exhaust system from the exhaust valves, an EGR system for controlling recirculation of exhaust flow from the exhaust system to the combustion chambers comprising an individual electric-actuated EGR valve associated with each respective combustion chamber for controlling the exhaust recirculation to the respective combustion chamber independent of the exhaust gas recirculated to any other combustion chamber, and an electric controller for controlling each valve individually in relation to one or more input parameters to the electric controller, the method comprising controlling individual EGR valve operation through a respective map of the respective combustion chamber&#39;s EGR requirements that is contained in the electric controller. 
     Still another aspect of the present invention relates to an EGR valve comprising a ferromagnetic shell comprising a cylindrical side wall, a transverse end wall at an axial end of the side wall, the end wall containing a valve seat circumscribing a first port, a second port in the side wall proximate the end wall, a valve element that is selectively positionable relative to the valve seat to selectively control EGR flow between the two ports, the side wall comprising an internal shoulder spaced beyond the second port relative to the end wall, a shield disposed within the shell and having an outer margin seated on the shoulder and an inner margin circumscribing the valve element, the inner margin being spaced toward the end wall relative to the outer margin, a bearing guide disposed within the shell seated on the outer margin of the shield and providing guidance for the valve element, a first ferromagnetic pole piece disposed within the shell against the bearing guide, an electromagnet coil disposed within the shell beyond the first pole piece relative to the bearing guide, a second ferromagnetic pole piece disposed within the shell and cooperating with the first pole piece to axially capture the coil, and with the shell side wall, form a solenoid, the solenoid further comprising an armature reciprocal within the coil and joined to the valve element, and a cap closing the end of the shell opposite the end wall. 
     Still another aspect of the present invention relates to an exhaust gas recirculation rail assembly comprising an exhaust gas recirculation rail forming an exhaust gas recirculation manifold adapted to be communicated to exhaust gas from an internal combustion engine, plural electricactuated EGR valves mounted on the rail, each comprising its own inlet port communicated to the exhaust gas recirculation manifold and its own outlet port, each outlet port adapted to be communicated to a respective engine combustion chamber to provide for controlled recirculation of exhaust gas to a respective combustion chamber independent of exhaust gas recirculated to other combustion chambers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more presently preferred embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention. 
     FIG. 1 is a schematic diagram of an internal combustion engine comprising an injector EGR system according to the present invention. 
     FIG. 2 is a longitudinal cross section view through an embodiment of injector EGR valve used in the injector EGR system of FIG.  1 . 
     FIG. 3 is a fragmentary elevational view, partly in cross section, of an assembly containing a number of injector EGR valves for a corresponding number of engine cylinders and adapted to be mounted on an engine. 
     FIG. 4 is a block diagram of a portion of an engine electronic control unit, or ECU, for operating individual injector EGR valves according to requirements for individual engine cylinders. 
     FIG. 5 is a longitudinal cross section view through another embodiment of injector EGR valve used in the injector EGR system of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a portion of a multi-cylinder internal combustion engine  200  that includes injector EGR valves  20  embodying principles of the present invention. Engine  200  comprises an intake system  202  comprising runners  204  through which combustible fuel-air charges are introduced into the engine cylinders at proper times during the engine cycle, then combusted in the cylinders to power the engine, and finally exhausted through an exhaust system  206 . A conduit  208  is tapped into exhaust system  206  to supply exhaust gas to EGR valves  20 . Each EGR valve  20  controls the introduction of exhaust gas into a respective runner  204  leading to a respective cylinder. 
     An engine management computer  210 , sometimes referred to as an electronic control unit or ECU, receives various input signals related to engine operation, processes certain of these signals according to stored algorithms, and issues control signals to EGR valves  20 . Each EGR valve  20  is opened by the corresponding control signal during a portion of the intake stroke of the corresponding engine cylinder, causing a controlled amount of exhaust gas to dope the incoming fuel-air charge. By placing an individual electric-actuated EGR valve  20  in association with each cylinder, the EGR doping of each cylinder may be controlled independent of the EGR doping of the others, and this allows EGR flow to each cylinder to be uniquely tailored to the particular requirements of a cylinder. This procedure can be beneficial to attainment of compliance with relevant exhaust gas emission regulations and/or specifications. 
     FIG. 2 shows an embodiment of EGR valve  20  to comprise a body  22  having an imaginary longitudinal axis  24 . Body  22  comprises a walled ferromagnetic shell  26  coaxial with axis  24 , a non-metallic end cap  27  closing an otherwise open axial end of shell  26 , a valve mechanism  28  at the opposite axial end of shell  26 , and a solenoid actuator  30  within shell  26  for operating valve mechanism  28 . At its axial end that contains valve mechanism  28 , shell  26  comprises a circular end wall  34 . Shell  26  further comprises a circular cylindrical side wall  36  extending from end wall  34  to cap  27 . Several through-holes in side wall  36  proximate end wall  34  form an inlet port  38  of valve  20 . At the center of end wall  34 , shell  26  has a circular through-hole forming an outlet port  40 . A radially inner margin of end wall  36  surrounding outlet port  40  comprises an inward turned circular lip that provides a circular valve seat  42  of valve mechanism  28 . A circular flat disk  44  and a cylindrical pin  46  form a valve element  48  of valve mechanism  28 . 
     Valve element  48  is disposed in association with solenoid actuator  30  and valve seat  42  for selectively opening and closing a flow path through a portion of the interior of valve body  22  between inlet port  38  and outlet port  40 . The flow path and direction of flow are depicted by arrows  50 . FIG. 2 shows the radially outer margin of disk  44  seating on valve seat  42 , closing the flow path. 
     A bearing  52  of suitable bearing material is disposed within shell  26  for guiding the travel of valve element  48 . Bearing  52  has a circular shape whose outer perimeter is fitted to the inner surface of side wall  36  proximate inlet port  38 . At its center, bearing  52  has a hub  54  containing a circular through-hole that is coaxial with axis  24 . Pin  46  passes through this through-hole with a close sliding fit by virtue of which bearing  52  guides valve element  48  for travel along axis  24 . 
     At one end, pin  46  has a neck  56  that passes through a small through-hole  58  in the center of disk  44 . The two parts are united by a joint that may be created by deforming the end of neck  56  against the margin of hole  58  at one face of disk  44  to force the margin of hole  58  at the opposite disk face against a shoulder at the junction of neck  56  and pin  46 . 
     Solenoid actuator  30  comprises an electromagnet coil  61  disposed on a non-metallic bobbin  62  coaxial with axis  24  within shell  26 . Actuator  30  also comprises a stator that includes two ferromagnetic pole pieces  64 ,  66  that are disposed respectively at respective opposite ends of coil  61  and bobbin  62 . Respective outer perimeters  68 ,  70  of pole pieces  64 ,  66  respectively, are fitted to side wall  36  at locations spaced axially along shell  26 . Pole piece  64  is imperforate while pole piece  66  has a circular through-hole  65  at its center. 
     Actuator  30  further comprises a ferromagnetic armature  78  having a generally cylindrical shape arranged coaxial with axis  24 . A circular, cylindrical sleeve  79  of non-ferromagnetic material, a non-magnetic stainless steel for example, is disposed within the bore of bobbin  62  coaxial with axis  24  to provide guidance for axial travel of armature  78 . One end of sleeve  79  is open to allow armature  78  to enter; the other end  80  is closed. This closed end  80  has a taper for seating within a similarly tapered depression  81  centrally formed in pole piece  64 . The axial end of armature  78  that confronts closed end  80  also has a similarly tapered shape, and at its center, a blind hole  82 . The opposite axial end of armature  78  has a blind hole  83  at its center. The end of pin  46  opposite neck  56  is received in hole  83  where the pin and armature are joined. 
     One axial end of a helical, compression, armature-bias spring  86  is received in blind hole  83 . The opposite end of the spring bears against closed end  80  of sleeve  79 . In this way, spring  86  biases armature  78  to seat the outer margin of disk  44  on seat  42  thereby closing the flow path through valve  20  between ports  38  and  40 . 
     Coil  61  comprises magnet wire wound around bobbin  62 . Respective terminations of the magnet wire are electrically joined to respective electric terminals  94  mounted on bobbin  62 . Free ends of terminals  94  protrude through end cap  27  where they are girdled by a surround  96  formed in end cap  27  to create an electric connector  98  to which a mating connector (not shown) may be connected to place coil  61  as a load in an electric control circuit for operating valve  20 . Such a circuit is part of the controller, or engine management computer, depicted by the block  210  in FIG.  1 . 
     The upper end of shell  26  has an outward turned lip  100  onto which end cap  27  is snapped and retained in place by one or more catches  102  on the cap rim. One further part of valve  20  is a circular, cup-shaped shield  104  whose outer perimeter seats on an internal shoulder  109  of shell  26 . The outer perimeter margin of bearing  52  in turn seats on the outer perimeter margin of shield  104 . A ring-shaped wave spring  112  is disposed circumferentially about pin  46  to act between bearing  52  and bobbin  62  to maintain to the described relationship of internal parts within the interior of shell  26 . 
     Shield  104  is imperforate except for a hole  105  at its center providing clearance to pin  46 . Shield  104  aids in directing hot exhaust gas flow passing through valve  20 , deflecting the gas and heat away from actuator  30 . The various internal parts of valve  20  fit together in a manner that prevents exhaust gas from intruding past actuator  30  and escaping to atmosphere. 
     The exterior of side wall  36  slightly beyond inlet port  38  relative to end wall  34  contains a screw thread  106  via which body  22  is threaded into a complementary threaded mounting hole in an engine in a gas-tight manner to place inlet port  38  in communication with engine exhaust gas and outlet port  40  in communication with induction flow into a corresponding engine cylinder, such as by communication with a runner  204 . 
     Pole pieces  64 ,  66 , the intervening portion of shell  36 , and armature  78  form a somewhat torroidal-shaped magnetic circuit that includes a circular annular air gap  120  between the armature and pole piece  66  at hole  65  and a larger air gap  121  between the opposite end of the armature and pole piece  64 . The magnetic circuit extends from one side of air gap  121 , through pole piece  64 , through side wall  36 , through pole piece  66 , across air gap  120  to armature  78 , and through the armature back to the other side of air gap  121 . 
     When actuator  30  is energized by flow of electric current in coil  61 , an electromagnetic force acts on armature  78  in an axial direction away from outlet port  40 . A sufficiently large current flow creates a force that is sufficiently large to overcome the bias of spring  86 . This imparts travel to valve element  48  in the direction of unseating from valve seat  42  thereby opening valve  20 . Exhaust gas can now pass from inlet port  38  along the flow path represented by arrows  50  and exit through outlet port  40 . When the current terminates, spring  86  re-closes valve  20  by re-seating valve element  48  on valve seat  42 . 
     Because each EGR valve  20  injects only an amount of exhaust gas needed for one engine cylinder, it can be made relatively small and compact. The valve can be mounted in an exhaust gas recirculation rail to form an exhaust gas recirculation rail assembly that can be mounted on an engine to associate each injector EGR valve outlet port with a respective cylinder intake runner. FIG. 3 shows such an exhaust gas recirculation rail assembly  160 . 
     Exhaust gas recirculation rail assembly  160  comprises a rail member  162  containing a number of individual injector EGR valves  20  corresponding to a like number of engine cylinders. For example, a four-cylinder in-line engine would have a rail member  162  containing four mounting sockets  164  at suitable locations along its length. Each socket comprises aligned holes through opposite portions of the wall of member  162 , one being threaded to receive the valve thread  106 . Each valve  20  is mounted in a respective socket  164  to place each valve&#39;s inlet port  38  in communication with the interior of rail member  162 . The mounting is gas-tight so that exhaust gas does not leak to atmosphere. The interior of rail member  162  is effectively a manifold to which conduit  208  supplies hot engine exhaust gas for distribution to the individual valves  20 . Each valve  20  is provided with a nozzle  168  that protrudes beyond end wall  34  to be seated in gas-tight manner to a hole in a wall of a respective engine runner  204 . Each nozzle  168  communicates the respective outlet port  40  to the respective runner. Hence when a respective valve  20  is operated open, exhaust gas is introduced through it to the respective runner  204  for entrainment with induction flow into the respective engine cylinder. An assembly  160  can provide certain advantages. All valves  20  can be assembled to member  162  and the assembly  160  tested before it is installed in an engine. A single conduit  208  can supply exhaust gas from exhaust system  206  to the manifold provided by member  162 , thereby avoiding multiple individual conduits for the multiple individual valves. 
     FIG. 4 shows detail of ECU  210  that adapts individual valves  20  to individual engine cylinders. In certain engines the EGR requirements of individual cylinders may vary from cylinder to cylinder for one or more different reasons. In a mass-produced engine model, the EGR requirements of the engine cylinders may be mapped on the basis of various parameters. A map of each cylinder&#39;s requirements for a particular engine model is programmed in ECU  210 . These maps are shown by blocks MAP 1 , MAP 2 , . . . MAPN, in FIG.  4 . Hence, when the engine is operated, various operating parameters are sensed and utilized as inputs to the respective maps to cause the amount of exhaust gas recirculated to each cylinder to be tailored to the particular cylinder&#39;s requirements. 
     FIG. 5 discloses another embodiment of EGR valve  20 ′. Various component parts of valve  20 ′ correspond either exactly, or closely, to like component parts of valve  20  that have already been described. Such component parts of valve  20 ′ are identified by the same base reference numerals as corresponding component parts of valve  20 , but primed. Given the foregoing detailed description of valve  20 , detailed description of valve  20 ′ will hereinafter be given only with respect to certain differences between the two embodiments. 
     In valve  20 ′, the circular lip of end wall  36 ′ that contains valve seat  42 ′ is turned outward, and pin  46 ′ is sufficiently long to allow disk  44 ′ to be disposed on the exterior of shell  26 ′. Armature  78 ′ has an external shoulder seating one end of spring  86 ′. The opposite end of spring  86 ′ seats on an inward turned flange at the lower end of sleeve  79 ′, which is in turn supported on the end of an upturned flange of pole piece  66 ′ that circumscribes hole  65 ′. Spring  86 ′ thereby biases valve element  48 ′ to seat disk  44 ′ closed on seat  42 ′. 
     The hole circumscribed by seat  42 ′ is inlet port  38 ′, and the holes in the adjacent side wall of shell  26 ′ form outlet port  40 ′. When valve  20 ′ is opened by displacing valve element  48 ′ downward from its FIG. 5 position, disk  44 ′ unseats to allow exhaust gas to enter through inlet port  38 ′, pass through the valve, and exit through the holes forming outlet port  40 ′. 
     In valve  20 ′, air gap  120 ′ is present between the upturned flange of pole piece  66 ′ and the lower end of armature  78 ′. The opposite air gap  121 ′ is present between the inside diameter of pole piece  64 ′ and the confronting side of armature  78 ′. When solenoid actuator  30 ′ is energized by a suitable electric current, armature  78 ′ is displaced downward against the force of spring  86 ′ to open the valve. When the current terminates, the compressed spring relaxes, returning armature  78 ′ upward and closing the valve. 
     In view of the reversal of the inlet and outlet ports in valve  20 ′ compared to valve  20 , it would be understood that the intake runners and exhaust manifold of an engine with which valves  20 ′ are used would be adapted to the port reversal. 
     It is also to be understood that because the invention may be practiced in various forms within the scope of the appended claims, certain specific words and phrases that may be used to describe a particular exemplary embodiment of the invention are not intended to necessarily limit the scope of the invention solely on account of such use.