Abstract:
An exhaust gas recirculation (EGR) system module is provided that integrally includes an electric vacuum regulator (EVR) valve and a differential pressure (DP) sensor. The DP sensor measures a differential exhaust pressure at locations upstream and downstream of an orifice in a gasket sealing the EGR system module to an intake manifold. The upstream measurement location is aligned with and particularly spaced from the orifice.

Description:
CROSS-REFERENCE TO CO-PENDING APPLICATIONS 
     This application claims the benefit of the earlier filing date of U.S. Provisional Application No. 60/149,330, filed Aug. 17, 1999, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an automotive exhaust gas recirculation (EGR) system module, and more particularly, to an EGR system having an electric vacuum regulator (EVR) valve and a differential pressure (DP) sensor combined in a single assembly. 
     BACKGROUND OF THE INVENTION 
     Various systems have been developed to reduce the emission of undesirable combustion products, such as nitrogen oxides (NOX), from internal combustion engines. One such system is the EGR system. In EGR systems, a portion of the engine exhaust is recirculated into the intake manifold where it mixes with incoming air. The mixture of the exhaust gases with the air-fuel mixture in the engine cylinders provides lower peak temperatures during combustion, resulting in a reduction in the quantity of NOX produced. 
     Known EGR systems utilize an EGR tube to divert a portion of the exhaust gases from an engine back into the intake manifold of the engine. A vacuum-operated EGR valve is arranged between the EGR tube and the intake manifold to regulate the flow of exhaust gases into the manifold. The intake manifold provides the vacuum source for operating the EGR valve. A first hose connects the manifold to an EVR valve, and a second hose connects the EVR valve to the EGR valve. The EVR valve receives a control signal from the engine control unit (ECU) and regulates the amount of vacuum provided to the EGR valve, which in turn limits the flow of exhaust gases into the intake manifold. 
     The ECU computes the EVR control signal based on a measurement of the differential pressure of exhaust gases between two points in the EGR tube. The differential pressure reflects the amount of flow of exhaust gases in the system. The pressure measurement is obtained using a DP sensor. The DP sensor operates by measuring the pressure of exhaust gases at locations on either side of a flow restriction, or orifice, in the EGR tube. The DP sensor continuously determines a delta pressure value for the exhaust gases and provides corresponding electronic data to the ECU. The ECU then uses this data to compute the EVR control signal. 
     There are several drawbacks associated with known EGR systems. The individual sensors and actuators used in these systems each require mounting brackets, electrical connections, and input and outlet hoses. Further, the DP orifice and hose connections on the EGR tube require additional manufacturing steps during production of the tube. Finally, the components in proximity to the exhaust system must be made from special heat-resistant materials to allow them to withstand the heat produced by the exhaust gases. The additional, specialized parts and the added manufacturing and assembly steps result in high production costs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system module integrating an EGR system, an EVR valve, and a DP sensor into a single unit. This system module can be mounted directly on an intake manifold of an internal combustion engine. Moreover, a single, common port on the intake manifold can provide a vacuum input connection to the EVR and the DP sensor of the system module. 
     The DP sensor measures exhaust pressure differential at locations upstream and downstream of an orifice that can be formed in a gasket sealing the EGR valve to the intake manifold. The upstream measurement location is in an EGR body, and the downstream location is in the intake manifold. Both orifices are located downstream of the EGR valve. 
     The present invention provides a system module for recirculating exhaust gases from an internal combustion engine to an intake manifold of the internal combustion engine. The system module comprises a body including a passageway extending between an inlet and an outlet, the passageway communicating a flow of the exhaust gases; an orifice constricting the flow of the exhaust gases proximate the outlet; a valve located in the passageway between the inlet and outlet, the valve regulating the flow of the exhaust gases; and a port extending through the body and in fluid communication with the passageway, the port being aligned with the orifice along a common axis. 
     The present invention also provides an exhaust gas recirculation module. The module comprises a valve assembly including a body having a passageway and including a pintle controlling a flow of exhaust gases through the passageway, the exhaust gases having a pressure; a pressure sensor coupled to the valve assembly; and a pressure communication pathway providing fluid communication between the passageway and the pressure sensor, the pathway communicating the pressure of the exhaust gases to the pressure sensor. 
     The present invention further provides a method of determining exhaust gas pressure. The exhaust gas is recirculated from an internal combustion engine to an intake manifold of the internal combustion engine. The method comprises providing a body including a passageway extending between an inlet and an outlet, the passageway communicating a flow of the exhaust gases; providing an orifice constricting the flow of the exhaust gases proximate the outlet; integrally mounting an exhaust gas pressure sensor on the body; and aligning a port along a common axis with the orifice, the port extending through the body and providing fluid communication between the passageway and the exhaust gas pressure sensor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention and, together with the general description given above and the detailed description given below, serve to explain features of the invention. 
     FIG. 1 is a front view of an EGR system module according to the claimed invention. 
     FIG. 2 is a left-side view of the EGR system module shown in FIG.  1 . 
     FIG. 3 is a right-side view of the EGR system module shown in FIG.  1 . 
     FIG. 4 is a top view of the EGR system module shown in FIG.  1 . 
     FIG. 5 is a cross-section view taken along line V—V in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-5 illustrate an EGR system module  10  including an upper body  12  integrally connected with an EVR  50  and a DP sensor  60 . The EVR  50  includes a cap  52  with a filter inside the cap  52 . The EVR  50  and the DP sensor  60  are in fluid communication via a connection  70 . The DP sensor  60  is integrally connected with the upper body  12  via mounting rails  14 . A multiple pin connector  62  for electrically interconnecting the EGR system module  10  to an ECU (not shown) can be integrally formed with the DP sensor  60 . 
     Examples of EVR valves that may be used are disclosed in commonly assigned U.S. Pat. No. 5,448,981 to Cook et al. and U.S. Pat. No. 5,967,172 to Cook, which are incorporated herein in their entirety by reference. 
     The EGR system module  10  includes an EGR body  16  that is integrally connected with the upper body  12  via a cap  18 . Tabs  20  on the cap  18  can be deformed to clinch the upper body  12 . This arrangement allows the upper body  12  to be rotated to a desired angular orientation with respect to the EGR body  16  during assembly. Thus, the EVR  50  and the DP sensor  60  can be oriented as desired in the finished EGR system module. 
     The EGR body  16  includes an exhaust gas inlet  22 , which is adapted to be connected to an exhaust gas supply (not shown), and an exhaust gas outlet  24 , which is adapted to be connected to an intake manifold (not shown). A gasket orifice  26  can be located at the exhaust gas outlet  24  to develop a pressure differential on either side of the gasket orifice  26  and to provide a seal for the connection to the EGR body  16 . Specifically, the gasket orifice  26  can be formed as a thin gasket that seals the EGR body  16  onto the intake manifold (not shown). The gasket orifice  26  can be made of stainless steel, which provides dimensional stability at high temperatures. Of course, other materials exhibiting similar properties can be used. 
     The relative spacing between a pintle  28  and a seat  30  regulates the flow of exhaust gas from the inlet  22  to the outlet  24 . The pintle  28  is slidably mounted with respect to the EGR body  16  by a bearing  32 . A stem shield  34  can protect the bearing  32  from contact with hot exhaust gases. The pintle  28  is connected to a diaphragm  36  that is clamped around its periphery between the upper body  18  and the cap  18 . The diaphragm  36  serves as an actuator wall that is movable in response to vacuum in a chamber  38 . As is known, the intake manifold (not shown) provides the source of vacuum for the chamber  38 . A spring  40  normally biases the diaphragm  36  and the pintle  28  to a closed position with respect to the seat  30 . 
     The DP sensor  60  measures the pressures on either side of the gasket orifice  26 . An internal passage  42  that extends through the EGR body  16 , and a hose  44 , provide the DP sensor  60  with the pressure signal from the upstream side, i.e., exhaust manifold side, of the gasket orifice  26 . The internal passage  42  is opposite the outlet  24  and aligned with the gasket orifice  26 . This arrangement ensures greater accuracy making EGR flow readings and simplifies the manufacturing process since the bores for the outlet  24  and the internal passage  42  can be machined in a single operation. The optimal range for the spacing “X” (see FIG. 5) between the gasket orifice  26  and the internal passage  42  has been found to be approximately 15 to 25 millimeters. 
     The DP sensor  60  can be connected directly to the intake manifold (not shown) on the downstream side of the gasket orifice  26 . The DP sensor  60  and the EVR valve  50  can both be connected to the intake manifold (not shown) via a common port that provides a source of vacuum for both the chamber  38  (as regulated by the EVR valve  50 ) and the DP sensor  60 . 
     The DP sensor  60  continually computes a differential pressure value on either side of the gasket orifice  26  and provides this data to an ECU (not shown), which uses this data to compute an EVR control signal. 
     While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.