EXHAUST GAS RECIRCULATION VALVE ASSEMBLY

Abstract: An exhaust gas recirculation valve assembly (10) for controlling the recirculation of exhaust gas in an internal combustion engine has an electrically operated valve member (28) that meters flow of exhaust gas through an exhaust gas chamber (14). The valve member has a valve stem (26) extending to an actuator assembly (30) which is isolated from the base (12) housing the exhaust gas chamber. The valve stem is surrounded by a pair of spring-biased seals (36,38) that seal openings ((24) around the valve stem into the actuator assembly and the exhaust gas chamber. The seal (36) closing the actuator assembly opening has an inverted, cup-shaped configuration which encloses the valve stem between the actuator assembly and the base thereby preventing impingement thereon of contaminants which could be carried into the actuator assembly.

Description: The present invention relates to an exhaust gas recirculation valve assembly for controlling recirculation of exhaust gas in an internal combustion engine according to the preamble of claim 1. Such an assembly in known from EP-A-234765 (corresponding to US-A-4725040). Electrically actuated exhaust gas recirculation (EGR) valve assemblies generally require isolation of the actuator assembly from the exhaust gas to assure proper operation. Separation of the actuator assembly from the base of the EGR valve assembly comes the need to prevent contamination, by foreign substances present in the engine compartment environment, of the actuator assembly and the valve stem which extends between the two components. Electrically actuated EGR valve assemblies heretofore proposed utilize a pair of spring-biased, disc-shaped seals around the openings where the valve stem enters the actuator assembly and the exhaust gas chamber. This configuration allows lateral movement of the seal to compensate for potential misalignment between the solenoid coil and the base. Such a configuration provides minimal protection to the valve stem which extends between the actuator assembly and the cover on the base. Another example of the prior art can be found in US-A-4805582. An exhaust gas recirculation valve assembly in accordance with the present invention is characterised by the features specified in the characterising portion of claim 1. The present invention provides an electrically actuated EGR valve assembly having a seal configured to protect the valve stem and stem-seal interface from contamination while allowing lateral movement of the seal and preventing heat build-up within the seal. In a preferred embodiment of an EGR valve embodying this invention, a valve member controls the flow of exhaust gas from an exhaust gas chamber. An actuator assembly including a solenoid coil, is located outside the exhaust gas chamber and is operatively connected with the valve member through the valve stem extending therebetween. The valve stem is surrounded by a pair of spring-biased seals that close the openings around the valve stem where it enters the actuator assembly and the exhaust gas chamber. The seal around the actuator assembly opening has an inverted cup-shaped configuration which comprises a central disc portion with an integral spring seat, a raised peripheral portion which engages the lower surface of the actuator assembly to seal the opening therein, and a downwardly extending skirt portion which extends to a location slightly above the base to shield the valve stem from impingement of contaminants present in the engine environment. Ventilation apertures extend circumferentially about the downwardly extending sides of the seal to prevent heat build-up within the enclosed seal while providing a high degree of protection to the valve stem. The present invention will now be described, by way of example, with reference to the following description and to the accompanying drawings, in which:- Figure 1 is a sectional view of an exhaust gas recirculation valve assembly embodying the present invention; and Figure 2 is an enlarged view of the armature-valve member-seal assembly disposed in the exhaust gas recirculation valve assembly of Figure 1. In Figure 1 there is shown an exhaust gas recirculation (EGR) valve assembly, designated generally as 10, for controlling the recirculation of exhaust gas in an internal combustion engine (not shown). The EGR valve assembly 10 has a base 12 with an exhaust chamber 14, an inlet and an outlet opening, 16 and 18 respectively, and a valve seat 20 formed about the circumference of the outlet opening 18. In an alternative embodiment, the valve seat may extend about the circumference of inlet opening 16. As shown in Figure 1, a plurality of inlet and outlet openings may be provided depending on the type and application of the EGR valve assembly 10, however, for purposes of description, one inlet opening 16 and one outlet opening 18 will be described. A cover 22 having an opening 24, which is generally aligned with the valve seat 20, closes chamber 14. A valve stem 26, having a valve member 28 mounted at a first end thereof, extends through opening 24 with valve member 28 mounted adjacent valve seat 20. An actuator assembly, designated generally as 30, is mounted in spaced relationship to base 12. The actuator assembly 30 comprises a solenoid coil 32 mounted on a bracket 33 in general alignment with valve seat 20. The solenoid coil 32 surrounds an armature 34 which is operatively attached to the second end of valve stem 26. A pair of seals 36 and 38 surround valve stem 26. Upper seal 36 has an inverted, cup-shaped configuration as shown in Figure 2, with a central disc portion 40, a raised peripheral portion 42 extending about the circumference of the disc portion 40, and a skirt portion 44 extending downwardly from the peripheral portion 42 to a position above lower seal 38. Upper seal 36 is formed from stainless steel sheet, or other suitable material. The disc portion 40 has a centrally located aperture 46 through which valve stem 26 passes. The edge of aperture 46 has a slight downward angle which increases resistance to water penetration at the valve stem-seal interface. The raised peripheral portion 42 has an inverted U-shaped configuration which forms a sealing surface 47, and inner and outer leg portions 48 and 50 respectively. The sealing surface 47 engages the lower surface of actuator assembly 30, see Figure 1, to prevent intrusion of contaminants into the actuator where they could degrade performance of the unit. Extending downwardly from outer leg portion 50 is skirt portion 44. The skirt portion 44 is integral with outer leg portion 50 and, as shown in Figure 1, has an axial length which provides a clearance between the lower edge of the skirt and lower seal 38. Only enough clearance is provided for proper operation of lower seal 38. Upper seal 36 substantially encloses valve stem 26, between actuator assembly 30 and base 12, within seal chamber 56 formed between valve stem 26 and skirt portion 44, to prevent impingement of contaminants thereon. As a result, such contaminants are not carried by the valve stem 26 into the actuator assembly 30. Because of the enclosure of the valve stem 26 it is necessary to provide a means for preventing heat build-up within the seal chamber 56. As a result, a plurality of circumferentially spaced ventilation apertures 54 are formed in outer leg portion 50 of raised peripheral portion 42. The ventilation apertures 54 allow heat to escape from seal chamber 56, however, since the ventilation apertures are positioned in opposition to inner leg portion 48, any contamination entering seal chamber 56 through the ventilation apertures 54 is deflected by inner leg portion 48, avoiding direct impingement onto valve stem 26. Lower seal 38 has a central disc portion 66 with a centrally located aperture 68 surrounding valve stem 26, and a peripheral rim 70 which engages cover 22 to seal the opening 24. To maintain upper and lower seals 36,38 in their respective positions relative to actuator assembly 30 and base 12, a spring 58 extends between an (integrally formed) spring seat 60 in the lower face of the central disc portion 40 of upper seal 36 and a corresponding spring seat 72 formed in the upper surface of lower seal 38. The force of spring 58 maintains sealing surface 47 of raised peripheral portion 42 in engagement with the lower surface of actuator assembly 30 and the peripheral rim 70 of lower seal 38 in engagement with the upper surface of cover 22. A second, valve return spring 62 extends between spring seat 60 and a valve stem spring seat 64 disposed axially midway of the upper and lower seals 36,38. In operation, valve return spring 62 biases valve stem 26 to engage valve member 28 with valve seat 20. When the solenoid coil 32 is energized, armature 34 and its associated valve stem 26 are lifted, against the bias of valve return spring 62, disengaging valve member 28 from valve seat 20 to allow recirculation of exhaust gas. It should be noted that solenoid coil 32 may not be precisely in alignment with valve seat 20. In this invention, however, the the armature-valve member-seal sub-assembly, shown in Figure 2, is able to float laterally to compensate for potential misalignment of the solenoid coil 32 while assuring that the actuator opening remains sealed. It will be appreciated that besides providing a means for sealing the interior of actuator assembly 30 from contamination, raised peripheral portion 42, of upper seal 36, effectively creates a clearance 'A', see Figure 1, between the lower face of actuator assembly 30 and the central disc portion 40 of upper seal 36. The result is an increase in potential armature travel and, consequently, valve travel. The present invention provides an efficient solution to undesirable contamination of the valve stem and actuator assembly in electrically actuated EGR valves having an electrical actuator which is isolated from the base assembly. The upper seal of the disclosed EGR valve assembly is configured to substantially enclose the valve stem as it extends between the actuator assembly and the base with means for preventing undesirable temperature build-up within the enclosure. Furthermore, the present invention includes a feature which increases the length of armature travel while allowing for lateral movement of the armature-valve member-seal sub-assembly relative to the solenoid coil while maintaining an adequate seal. Also, the construction of the upper valve seal of the present invention, which uses stainless steel sheet or other suitable material, allows for the inclusion of an integral spring seat in the lower surface of the central disc portion.

Claims: An exhaust gas recirculation valve assembly comprising a base (12) having a valve member (28) disposed therein for controlling exhaust gas flow therethrough, an actuator assembly (30) mounted in spaced relationship to the base, and a valve stem (26) extending between the actuator assembly and the valve member, the actuator assembly being energizable to move the valve stem and valve member in the base; a seal (36), disposed between the actuator assembly and the base, with a central disc portion (40) having an aperture (46) through which the valve stem extends, and a raised peripheral portion (42) extending about the circumference of the central disc portion; and means (58) for biasing the raised peripheral portion into sealing engagement with the actuator assembly thereby enclosing the interface between the actuator assembly and the valve stem to reduce impingement of contaminants thereon while permitting lateral movement of the valve stem relative to the actuator assembly; characterised in that the seal has a generally cup-shaped configuration with a skirt portion (44) extending away from the raised peripheral portion to a position adjacent the base to substantially enclose the valve stem and, a ventilation aperture (54) in the seal to promote air circulation through the seal. An exhaust gas recirculation valve assembly as claimed in claim 1, wherein the raised peripheral portion (42) has an U-shaped cross section, having radially inner and outer leg portions (48,50); the outer leg portion being integral with the skirt portion (44) and having the ventilation aperture (54) formed therethrough in opposition to the inner leg portion which thereby operates as a barrier between the ventilation aperture and the valve stem (26) to substantially prevent contaminants directly impinging on the valve stem. An exhaust gas recirculation valve assembly, as claimed in claim 2, wherein the raised peripheral portion (44) has a plurality of ventilation apertures (54) therethrough which are circumferentially spaced. An exhaust gas recirculation valve assembly as claimed in any one of claims 1 to 3, wherein the biasing means comprises a spring (58) surrounding the valve stem (26). An exhaust gas recirculation valve assembly as claimed in claim 4, wherein an integral spring seat (60) is formed in the central disc portion (40) for the spring. An exhaust gas recirculation valve assembly as claimed in any one of claims 1 to 5, wherein the base (12) has an exhaust gas chamber (14) with an inlet opening (16), an outlet opening (18), and a valve seat (20) surrounding one of said openings; a cover (22) closes the exhaust gas chamber and has an opening (24) generally aligned with the valve seat; the valve stem (26) extending through the opening in the cover; the valve member being mounted adjacent the valve seat at one end of the valve stem; the actuator assembly being at the other end of the valve stem, energization of the actuator assembly moving the valve member into and out of engagement with the valve seat; and the biasing means (58) being disposed between the seal and the cover.

Inventors: BARKER, CHARLES JEROME, CONKLIN, ROBERT JOHN, LIGGETT, MICHAEL DAVID, MEYER, KAREN MARIE
Applicants: GENERAL MOTORS CORPORATION
Application year: 1991
Main classification: F02M25
IPC codes: F02M25