Abstract:
An EGR valve apparatus regulates the amount of exhaust gas recirculated in an EGR system. The EGR valves are opened or closed by a rotatable shaft which is actuated by a motor. Alternatively, the valves can be balanced on the shaft, the valves moving in opposing direction during rotation. An inline poppet can be employed to overcome pressure in the system prior to movement of the valves. In another alternative embodiment, the motor rotates threaded shaft to move a pintle towards and away from an orifice.

Description:
This application is a continuation in part of PCT Application NO. PCT/US01/14200 filed on May 3, 2001, which claims priority to also provisional patent application Nos. 60/201,391 filed on May 3, 2000; 60/234,432 filed on Sep. 21, 2000 and 60/235,828 filed on Sep. 27, 2000. The PCT Application was published under PCT Article 21(2) in English. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to an exhaust gas recirculation (EGR) system for regulating the flow of an exhaust gas. 
     EGR systems are increasingly being utilized to improve the efficiency of engines and reduce the harmful effects of the exhaust gas on the environment. As an engine burns fuel, it produces an exhaust gas which contains unburned fuel and other impurities. In an EGR system, the exhaust gas is redirected through the engine to burn any unburned fuel remaining in the exhaust gas. Reburning the exhaust gas before it is released reduces the harmful effects of the exhaust gas on the atmosphere and enables the vehicle to meet government emission standards. 
     In order to recirculate the exhaust gas, EGR systems typically include a valve and a cooler. The valve regulates the amount of exhaust gas that is introduced back into the engine. The cooler cools the exhaust gas to a specified temperature which condenses the unburned fuel. 
     Prior EGR systems utilize a vacuum source with a diaphragm actuator to open and close the valve. The diaphragm actuator has a slow response time and is either open or closed with no intermediate valve position. One drawback to the prior art is that the slow response time of valves reduce the horsepower and efficiency of the engine, limiting the amount the EGR system may be used. 
     Hence, there is a need for an improved exhaust gas recirculation system for regulating the flow of an exhaust gas. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an exhaust gas recirculation system for regulating the flow of an exhaust gas. 
     The exhaust gas recirculation system includes an EGR valve apparatus which regulates the amount of exhaust gas that is recirculated in the system. In one embodiment, a motor rotates a shaft which opens or closes a plurality of valves. The amount of exhaust gas flowing through the EGR valve apparatus is proportional to the amount the valves are opened or closed. 
     In a second embodiment, a force balanced rotary EGR valve assembly including balance seat valves is utilized. When more exhaust is to enter a chamber, the shaft is rotated, moving a downward balanced seat rotary EGR valve downwardly out of the chamber against the flow of exhaust and an upward balanced seat rotary EGR valve upwardly into the chamber with the flow of exhaust. Rotating the shaft in the opposite direction reverses the movement of the valves, allowing less exhaust gas to enter the chamber. 
     A third embodiment includes an inline poppet located on each valve which opens to allow gas to enter the chamber before the EGR valve is opened to overcome the pressure in the system. A cam translates the rotary motion of the motor shaft to the linear motion of a valve shaft to open the EGR valve. 
     Alternatively, the motor rotates the motor shaft to pivot a balance arm in a fourth embodiment. A first end of the arm moves upwardly to raise an EGR valve, and a second end of the arm moves downwardly to lower an EGR valve, allowing more exhaust gas to enter the chamber. Reverse rotation of the shaft reverses the movement of the valves, allowing less exhaust gas to enter the chamber. 
     In a fifth embodiment, an air venturi apparatus is employed. The motor rotates a shaft of a poppet, separating a pintle from an orifice. The degree of separation of the pintle from the orifice allows a proportional amount of a fresh air/exhaust gas mixture to return to the system. 
     Accordingly, the present invention provides an exhaust gas recirculation system for regulating the flow of an exhaust gas. 
     These and other features of the present invention will be best understood from the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
     FIG. 1 illustrates a flow diagram for an exhaust recirculation system which regulates the flow of an exhaust gas; 
     FIG. 2 is a perspective view of a first embodiment of the valve apparatus of the present invention; 
     FIG. 3 illustrates a perspective view of a second embodiment of the valve apparatus employing a forced balanced seat EGR valve assembly; 
     FIG. 4 illustrates a cross sectional side view of the valves of the force balanced rotary EGR valve assembly of the second embodiment; 
     FIG. 5 illustrates an interior cross sectional view of a third embodiment of the valve apparatus with the force balanced rotary valves opened; 
     FIG. 6 illustrates an interior cross sectional view of a fourth embodiment of the valve apparatus; 
     FIG. 7 illustrates a perspective internal view of an air venturi assembly of a fifth embodiment of the present invention; and 
     FIG. 8 illustrates an interior cross-sectional view of an alternate fourth embodiment of the valve apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The exhaust gas recirculation (EGR) system, illustrated in FIG. 1, comprises an engine control unit (ECU)  10  which transits a pulse width modulated (PWM) signal  20  to a printed circuit board (PCB) pilot circuit  12 . A PWM signal  20  is not strong enough to operate a motor  14 , the pilot circuit  12  is connected to a second current source  18 , such as a battery, which increases the strength of the PWM signal  20 . The pilot circuit  12  then transmits a second signal  22  to the motor  14 , which actuates a valve apparatus  16  to control the flow of a fresh air/exhaust gas mixture back into the system. It is preferred that the motor  14  is an electric D/C motor  14 , preferably a monophase electromagnetic actuator. 
     The ECU  10  is programmed to operate the EGR system at certain customer specified duty cycles. As a vehicle travels at a constant speed, the ECU  10  transmits a signal to operate the EGR system at full capacity. However, when the vehicle requires maximum horsepower, such as during acceleration, the ECU  10  transmits the PWM signal  20  to close the valves apparatus  16 , to step exhaust gas recirculation. The ECU  10  is limited by being able to transmit a signal of no more than 1.3 amps. 
     FIG. 2 illustrates a first embodiment of the EGR valve apparatus  16  of the present invention. A non-contact sensor of the motor  14  receives a signal from the pilot circuit  12  and in response rotates a shaft  30  to proportionally open or close a plurality of valves  28 . The motor  14  is attached to a housing  42  by a bracket  34 , which provides support for the shaft  30  and withstands the torque produced as the shaft  30  rotates. 
     Each of the valves  28  includes an arm  44  connected to a disc  46  by a pin. As the shaft  30  rotates, the arm  44  pivots and the disc  46  moves, opening and closing the valves  28 . In this embodiment, each of the valves  28  are substantially positioned on the same side of the shaft  30 . 
     After the valves  28  have been opened, exhaust gas flows from the engine, which is fastened to the housing  42  at a first mounting face  24 , through an exhaust gas inlet  40 . The exhaust gas enters a chamber  36  and exits the valve assembly  16  through the outlet  38 . The exhaust gas then flows into a cooler, which is fastened to the housing  42  at a second mounting face  26 . While multiple valves are shown for increased exhaust gas flow, only one may be used if desired. 
     In a second embodiment, as illustrated in FIG. 3, a valve assembly  116  including force balanced seat rotary EGR valves  128  is utilized. As the motor  114  operates, the shaft  130  rotates to proportionally raise and lower the rotary EGR valves  128  allowing exhaust to enter the chamber  136  from the engine. While a pair of force balanced rotary EGR valves  128  are illustrated, any number may be utilized. In this embodiment, the rotary EGR valves  128  are positioned on opposite sides of the shaft  130 . 
     As illustrated in FIG. 4, each rotary EGR valve  128  includes a pintle  148  attached to a bottom portion  150  of a valve shaft  144 . When more exhaust is to enter the system, the shaft  130  is rotated so that the downward rotary EGR valve  128   a  moves downwardly out of the chamber  136  against the flow of exhaust, and the upward rotary EGR valve  128   b  moves upwardly into the chamber  136  with the flow of exhaust. The degree of rotation of the shaft  130  determines the amount the rotary EGR valves  128   a ,  128   b  are opened. It is preferred that the shaft  130  be rotated 20°, although other degrees of rotation are possible depending on system requirements. When less exhaust is to enter the system, the shaft  130  is rotated in the opposite direction, reversing the abovementioned movement of the valves  128   a ,  128   b . When no exhaust is to enter the system, the pintles  148  of the rotary EGR valves  128  fit securely into an orifice  146  cut into the first mounting face  24  of the housing  42 , preventing exhaust from being recirculated into the system. 
     As further illustrated in FIG. 4, an upper portion  152  of each valve shaft  144  is attached to a curved arm  154  secured to the motor shaft  130  by a pin  158 , the valve shaft  144  being positioned within an orifice  164  in the pin  158 . Wave washers  160  are utilized to reduce wear. A threaded nut  162  positioned on the upper portion  152  of the valve shaft  144  secures the assembly. 
     As the motor  114  rotates the shaft  130  according to the required input, the arms  154  pivot and transfer the rotational movement of the shaft  130  into the linear movement of the rotary EGR valves  128   a ,  128   b . A spring can be employed on the motor shaft  130  proximate to the motor  114  to prevent vibrations and to act as a fail safe mechanism to close the valves  128   a ,  128   b  if the motor  114  loses power. 
     FIG. 5 illustrates a third embodiment of the EGR valve assembly  216  in an open position. An inline poppet  266  located on the pintle  248  opens to allow gas to enter the chamber  236  before the EGR valve  228  is opened. This overcomes the pressure in the system, reducing the force needed to open the EGR valve  228 . The motor  214  rotates a shaft  230  which is connected to a cam  268 , the cam  268  translating the rotary motion of the motor shaft  230  to the linear motion of the valve shaft  244  and opens the EGR valve  228 . The degree of rotation of the motor shaft  230  determines the degree of the opening of the EGR valve  228 . Rotation of the motor shaft  230  moves the pintle  248  towards or away from the orifice  246  to allow the desired amount of exhaust gas to enter the chamber  236 . 
     FIG. 6 illustrates a fourth embodiment of valve assembly  316 . The motor  314  rotates a motor shaft  330 , pivoting a balance arm  372  so that a first end  374   b  of the arm  372  moves upwardly to raise the rotary EGR valve  328   b , and the second end  374   a  of the arm  372  moves downwardly to lower the rotary EGR valve  328   a . As the valves  328   a ,  328   b  move away from their respective orifices  346 , more exhaust gas is allowed to enter the chamber  336 . Reverse rotation of the shaft  330  reverses the movement of the valves  328   a ,  328   b . The degree of the opening of the valves  328   a ,  328   b  is determined by the ECU  10 . 
     FIG. 8 illustrates an alternate valve assembly  516  including a balance arm  572  moveable about a motor shaft  530 . A first valve  528   b  is attached to a first end  574   b  of the balance arm  572 , and a second valve  528   a  is attached to a second end  574   a  of the balance arm  572 . The motor (not shown) rotates the motor shaft  530  to pivot the balance arm  572 . Preferably, the valves  528   a  and  528   b  are covered by a plastic cover  566 . In one example, the plastic cover  566  is made of zytel. Shaft bushings (not shown) are preferably positioned around the shaft  530  to assist in alignment of the valves  528   a  and  528   b.    
     The first mounting face  524  of a housing  542  including a chamber  536  is fastened to an engine. When more exhaust gas is to enter the chamber  536 , the shaft  530  is rotated to pivot the balance arm  572  to open the valve assembly  516  such that the first end  574   b  of the arm  572  moves upwardly to raise the first valve  528   b , and the second end  574   a  of the arm  572  moves downwardly to lower the second valve  528   a . After the valves  528   a  and  528   b  have been opened, exhaust gas flows from the engine into the chamber  536  through exhaust gas inlets  540   a  and  540   b  in a cooler. The exhaust gas exits the chamber  536  through an outlet  538  for cooling. 
     When less exhaust is to enter the chamber  536 , the shaft  530  is rotated in the opposite direction to pivot the balance arm  72  to close the valve assembly  516  such that the first end  574   b  of the arm  572  moves downwardly to lower the first valve  528   b , and the second end  574   a  of the arm  572  moves upwardly to raise the second valve  528   a . The degree of rotation of the shaft  530  determines the amount the valves  528   a  and  528   b  are opened or closed. 
     Each valve  528   a  and  528   b  includes a pintle  548   a  and  548   b , respectively, attached to a bottom portion  550  of a valve shaft  544 . When no exhaust is to enter the housing  536 , the pintles  548   a  and  548   b  of the valves  528   a  and  528   b  fit securely into an orifice  546   a  and  546   b , respectively, in the first mounting face  524  of the housing  542 , preventing exhaust from entering the housing  536  through the inlets  540   a  and  540   b  and from being recirculating into the system. 
     As the valves  528   a  and  528   b  are moved and fluid flows through the orifices  546   a  and  546   b  into the chamber  536 , the valve  528   a  moves with the flow of the exhaust fluid and the valve  528   b  moves against the flow of exhaust fluid. As these forces are balanced, no additional forces are provided on the motor during movement of the valves  528   a  and  528   b.    
     The outer edge of the pintle  548   b  includes is angled upwardly. When the valve  528   b  is closed, the outer edge of the pintle  548   b  contacts the orifice  546   b , breaking off any soot from the exhaust that collects on the pintle  548   b . The outer edge of the pintle  548   a  is angled downwardly. Any soot accumulating on the pintle  548   b  will drain off the pintle  548   b . By eliminating the buildup of soot on the pintles  548   a  and  548   b , the sticking of the pintles  548   a  and  548   b  in the orifices  546   a  and  546   b  is reduced, creating a better seal between the pintles  548   a  and  548   b  and the orifices  546   a  and  546   b.    
     An arm  576  is received in a hole  578  in each end  574   a  and  574   b  of the balance arm  572 . An upper portion  558  of each valve shaft  544  is secured to each arm  576 . In one example, the upper portion  558  of each valve stem  544  is orbital riveted to the arm  576 , reducing and eliminating vibrations. As the balance arm  572  moves about the shaft  530 , the arms  576  pivot in the holes  578 , translating the rotary motion of the shaft  530  into the linear motion of the valves  528   a  and  528   b.    
     Each valve shaft  544  further includes a reduced diameter portion  554  received in a stem shield  556 . Each stem shield  556  includes an aperture  557  sized to receive the reduced diameter portion  554 . As the valves  528   a  and  528   b  are opened and closed, the interaction of the reduced diameter portion  554  and the stem shield  556  rubs off any soot and condensation, reducing any soot and condensation that forms at the interface  559 . 
     A portion of the valve shafts  544  are positioned in a cooling chamber  552 . The coolant enters a path  551  around the cooling chamber  552  through an inlet  550  and circulates around the valve shafts  544  to provide cooling. The coolant exits the cooling chamber  552  through an outlet (not shown) located next to the inlet  550 . The cooling chamber  552  is secured to the housing  542  by attachment members  567  to eliminate any vibrations. Preferably, the attachment members  567  are bolts. 
     A bushing  560  positioned around the each of the valve shafts  554  is received in the coolant chamber  552 . The bushing  560  is preferably made of sintered bronze or vespel to reduce friction between the bushing  560  and the valve shaft  544 . The interaction of the bushing  560  and the valve shaft  544  also reduces and eliminates soot and condensation that build up on the valve stem  544  and bushing  560  interface. A lip seal  562  is fitted on the top of the bushing  560  and is retained by a seal retainer  564 . 
     The valve apparatus  516  further includes a resilient member  568  positioned around the shaft  530 . In one example, the resilient member  568  is a spring. The resilient member  568  biases the valves  528   a  and  528   b  to the closed position. In the event of a power loss, the resilient member  568  closes the valve assembly  516  and acts as a fail-safe mechanism. 
     FIG. 7 illustrates an air venturi valve apparatus  416 . Fresh air enters from a fresh air inlet  432  in a first elongated tube  424  and exhaust gas enters from an exhaust gas inlet, mixing in a chamber  436  of a housing  442 . The fresh air/exhaust gas mixture exits the housing  442  through a fresh air/exhaust gas mixture outlet  438  in a second elongated tube  426 , leading back to the system. 
     When the fresh air/exhaust gas mixture is to be released back into the system, the motor  414  rotates a shaft  444  of a poppet  430  threaded in the first elongated tube  424 , separating a pintle  448  from an orifice  446 . As the pintle  448  moves away, the fresh air/exhaust gas mixture passes through the orifice  446  and into the system. The farther away the pintle  448  is positioned from the orifice  446 , the more fresh air/exhaust gas mixture is allowed to pass through the orifice  446  and back into the system. 
     By rotating the threaded valve shaft  444 , the pintle  448  of the poppet  430  can be repositioned depending on the system requirements. When no fresh air/exhaust gas mixture is to be allowed back into the system, the valve shaft  444  is rotated such that the pintle  448  is secured in the orifice  446 , blocking the flow of fresh air/exhaust gas into the second elongated tube  426  and into the system. 
     There are many advantages to operating the EGR system with the electric D/C motor  14 . First, the motor  14  can proportionally open the valves  28 , allowing for various flow ranges. Secondly, the motor  14  achieves a faster response than the vacuum actuators of the prior art. Additionally, this EGR system reduces space requirements within the engine compartment due to the compact size of the motor  14 . 
     The foregoing description is exemplary rather then defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention.