Patent Publication Number: US-2018030936-A1

Title: Exhaust gas recirculation valve having crowned spline

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to valves and particularly to exhaust gas recirculation valves and more particularly to an exhaust gas recirculation valve including a butterfly valve attached to a valve shaft with crowned splines for being selectively rotated by an actuator. 
     Description of Related Art 
     Exhaust gas from an internal combustion engine can be used to alter the operating parameters of the engine. The flow of exhaust gas is controlled through valves within or exposed to the exhaust system of the engine. Exhaust gas emissions can be lowered though the use of exhaust gas recirculation (EGR) to recirculate a portion of the exhaust gas to the air intake steam. EGR valves provide for a reduction in the formation of nitrogen oxides (NO x ) during combustion by redirecting a portion of the exhaust gas to the air intake system of the engine. The recirculated exhaust gas is mixed with incoming fresh air, resulting in a lower combustion temperature, which reduces or limits the production of NO x . 
     As the EGR valve is exposed to exhaust flow for extended periods, wherein the velocity of the exhaust flow can vary substantially, the EGR valve must withstand significant stress. 
     The need exists for an EGR valve that can accommodate the intended operating environment as well as manufacturing tolerances without experiencing excessive wear or deterioration that can lead to failure or a material reduction in performance characteristics. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present disclosure to provide an exhaust gas recirculation valve assembly with improved resilience. 
     A first exemplary embodiment of the present disclosure provides an exhaust gas recirculation valve assembly including a housing having an exhaust passage for passing engine exhaust; a valve shaft rotatably mounting to the housing for rotation relative to the housing, the valve shaft including a plurality of radially extending crowned splines; and a valve body attached to the valve shaft to rotate with the valve shaft within the exhaust passage to vary occlusion of the exhaust passage. 
     A second exemplary embodiment of the present disclosure provides an exhaust gas recirculation valve assembly including a housing having an exhaust passage for passing engine exhaust; a valve shaft rotatably mounting to the housing for rotation relative to the housing, the valve shaft carrying a valve body; a drive shaft; and a splined interface between the valve shaft and the drive shaft, one of the valve shaft and the drive shaft including a plurality of projecting crowned splines and a remaining one of the valve shaft and the drive shaft including a sleeve having an engaging surface for cooperatively engaging the plurality of crowned splines. 
     A third exemplary embodiment of the present disclosure provides for an exhaust gas recirculation valve assembly including a housing having an exhaust passage for passing engine exhaust; a valve shaft rotatably mounting to the housing for rotation relative to the housing, the valve shaft having an inner section located within the exhaust passage and an outer section located outside the exhaust passage, the outer section including one of a plurality of radially outwardly extending crowned splines and a sleeve having a plurality of radially inwardly extending splines; a valve body attached to the valve shaft to rotate with the valve shaft within the exhaust passage to vary occlusion of the exhaust passage; and a drive shaft having a remaining one of the plurality of radially outwardly extending crowned splines and the sleeve having a plurality of radially inwardly extending splines to define a splined interface for imparting a rotation of the drive shaft to the valve shaft. 
     The following will describe embodiments of the present disclosure, but it should be appreciated that the present disclosure is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principle. The scope of the present disclosure is therefore to be determined solely by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  presents an exemplary valve assembly suitable for use in practicing exemplary embodiments of the present disclosure. 
         FIG. 2  presents another exemplary valve assembly suitable for use in practicing exemplary embodiments of the present disclosure. 
         FIG. 3  presents a cross sectional view of an exemplary valve assembly suitable for use in practicing exemplary embodiments of the present disclosure. 
         FIG. 4  presents an exemplary shaft suitable for use in practicing exemplary embodiments of the present disclosure. 
         FIG. 5  presents a close-up view of the end portion of an exemplary shaft suitable for use in practicing exemplary embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Exemplary embodiments of the present disclosure provide an exhaust gas recirculation (EGR) valve assembly. While the valve described herein can have a variety of configurations, (e.g., a sliding valve, a poppet valve, or a valve-in-bore system) for purposes of this disclosure, the present system is set forth in terms of an EGR valve operable to rotate between a flow position and a no-flow or flow restricting position. This includes quarter turn valves, wherein a representative valve configuration is a butterfly valve. 
     Referring to  FIGS. 1 and 2 , illustrated is EGR valve assembly  102 , which includes a housing  124  (shown in  FIG. 2 ), a butterfly valve assembly  104  and an actuator  106 . 
     The housing  124  defines an exhaust passage  125  (shown in  FIG. 2 ) for passing engine exhaust. The exhaust passage  125  has an inlet and an outlet. Although the exhaust passage  125  can have any of a variety of cross section profiles, for purposes of description, the cross section profile is set forth as circular. 
     The housing  124  includes a pair of opposing bearings intermediate the inlet and the outlet. The bearings can be integral with the housing or an insert to the housing or affixed to the housing. 
     The butterfly valve assembly  104  includes a valve body  108  and a valve shaft  110 , wherein the valve body  108  is attached to the valve shaft  110  for rotation with the valve shaft  110 . 
     The valve body  108  of the butterfly valve assembly  104  includes wall contact type valve bodies and  90 -degree closing type valve bodies. The wall contact type valve body can include an elliptical valve plate (as depicted in  FIG. 1 ) that is placed on the valve shaft  110  in bore  111 . The valve body  108  is then rotated about the axis of the valve shaft  110 , so that flow restriction is a function of rotation. In a closed position, the valve body  108  contacts the wall of the exhaust passage  125 . 
     The valve body  108  of the 90-degree closing type butterfly valve assembly  104  employs a round valve plate (as shown in  FIG. 1 ) having a diameter that is slightly smaller than a diameter of the exhaust passage  125 . The valve body  108  rotates about a centerline of the bore  111 . In its closed position, the valve body  108  is perpendicular to the exhaust flow through exhaust passage  125 . 
     Thus, the valve body  108  is a plate or disk attached to the valve shaft  110 , wherein the valve body  108  can be substantially parallel or perpendicular to the flow through the exhaust passage  125 . 
     The valve body  108  can be symmetrically attached to the valve shaft  110  or have a planar offset, depending on the desired operating characteristics. That is, the axis of rotation of the valve shaft  110  can lie in a plane of the valve body  108 . Alternatively, the axis of rotation of the valve shaft  110  can be spaced or offset from the plane of the valve body  108 . Similarly, the valve shaft  110  can lie in the plane of the valve body  108  and pass through a centroid or line of symmetry of the valve body  108 . Alternatively, the valve shaft  110  can lie in the plane of the valve body  108  and can have an asymmetric offset from the centroid or line of symmetry of the valve body  108 . The asymmetric offset configuration provides for the generation of a moment force on the flow side for closing the valve body  108 . On the flow side for opening the valve  104 , less area on the armature is exposed. Thus, the force required for opening the valve  104  is decreased. The net moment force is greater on the flow side for closing the valve  104 , thereby enhancing sealing. It is understood the selection and amount of offset is a design parameter and within the scope of the present system. 
     The valve shaft  110  is rotatably mounted to opposing bearings  113  for rotation relative to the housing  124  about a longitudinal axis of the valve shaft  110 . It is understood, the valve shaft  110  can carry the bearings  113 , which then provide the interface to the housing  124 . In one configuration, the valve shaft  110  is transverse to the exhaust passage  125 . However, it is understood the longitudinal axis of the valve shaft  110  can be inclined relative to the exhaust passage  125 . 
     The valve shaft  110  is rotated about the longitudinal axis to vary the orientation of the valve body  108  in the exhaust passage  125 , thereby controlling or regulating the flow of exhaust gas through the exhaust passage  125 . 
     The valve shaft  110  is selectively rotated by the actuator  106 . That is, the actuator  106  imparts a rotation to, or drives the valve shaft  110 . The actuator  106  can include any of a variety of mechanisms including servos, hydraulic servos, solenoids and stepper motors. For purposes of this disclosure, the actuator  106  includes or provides the motive force to a drive shaft  115 , which in turn imparts rotation to the valve shaft  110 . In those configurations employing a hydraulic actuator, it is understood a control valve, including a spool valve can be employed to impart rotation of the valve shaft  110 . It is further understood the actuator  106  can include a solenoid wherein the control valve is biased to provide the EGR valve  102  to function as a proportional valve. 
     The present system can employ the actuator  106  to rotate the valve shaft  110 , which in turn positions the butterfly valve  104  to control the amount of exhaust flow, and exhibit a proportional, or linear response over their entire range of valve-opening positions. In some configurations, an electronic component is employed for adjustment in controlling the flow of the exhaust gas. The electronic component may trigger actuation of the valve  102  based on sensed engine operating parameters such as but not limited to, engine temperature, oil pressure or engine rpm. 
     In one configuration, the interface for the transfer of power from the actuator  106  to the valve shaft  110  is a crowned splined interface  117 . That is, the interface between the valve shaft  110  and the drive shaft  115  includes crowned splines and a corresponding engaging surface. As depicted in  FIGS. 3, 4, and 5 , the crowned splined interface  117  can include one of the valve shaft  110  and the drive shaft  115  including a plurality of projecting crowned splines  119  (shown in  FIGS. 4 and 5 ) and a remaining one of the valve shaft  110  and drive shaft  115  includes a sleeve having an engaging surface for cooperatively engaging the plurality of crowned splines  119 . 
     Although it is contemplated the crowned splines  119  can be disposed on either the valve shaft  110  or the drive shaft  115 , it is contemplated in one configuration, the crowned splines  119  are formed on the valve shaft  110  and the corresponding engaging surface is formed in the sleeve or drive shaft  115  of the actuator  106 . 
     In one configuration for imparting rotation of the valve shaft  110  (shown in  FIGS. 1 and 2 ), the valve shaft  110  includes or is connected to a pinion  112  which is turn is driven by a rack  114 , wherein the rack  114  is moved by any of a variety of mechanisms, such as a hydraulic actuator. The valve shaft  110  includes a plurality of crowned splines  119  and the drive shaft  115 , rotated by the pinion  112 , defines the sleeve having the engaging surface for cooperatively engaging the crowned splines  119 . 
     In one configuration, the crowned splines  119  on the valve shaft  110  number between approximately 8 and approximately 24. It should be appreciated that the number of crowned splines  119  on valve shaft  110  is dependent on the circumference of valve shaft  110  and expected stress loads imparted onto crowned splines  119 . That is for instance, a valve shaft  110  having a circumference of 2.215 inches, will also have approximately 16 crowned splines  119 . Embodiments of valve shaft  110  provide that the entire circumference of valve shaft  110  need not include a crowned spline  119  adjacent to another crowned spline  119 . Embodiments of valve shaft  110  provide for one or more spaces or gaps extending along the longitudinal axis of valve shaft  110  between a pair of crowned splines  119 . Spaces or gaps between crowned splines  119  provide a mechanism for alignment of valve shaft  110  with pinion  112 . Likewise, embodiments of pinion  112  include a corresponding tooth for engagement with spaces or gaps. The crowned splines  119  have a length along the valve shaft  110  between approximately 0.75 inches and approximately 1.0 inch. Embodiments of crowned splines  119  can also have a length along the valve shaft  110  between approximately 1.0 inches or less. Again, the length of the crowned splines  119  is dependent on expected stress loads imparted onto the crowned splines  119 . For a valve shaft  110 , the circumference can be between approximately 1.178 inches and approximately 3.252 inches. 
     The curvature or crown of the splines  119  can be defined be a radius of curvature swept about a plane that encompasses the longitudinal axis of the valve shaft  110 , wherein the entire free edge of the crowned spline  119  is entirely defined by the radius of curvature. Alternatively, only the ends of each crowned spline  119  may be defined by a radius of curvature. Thus, between approximately 20% and approximately 100% of the length of the spline  119  can be defined by the radius of curvature. 
     Depending on the imposed radius of curvature, the height of the crowned spline  119  may vary from approximately 20% to the full height at the ends to the full height. 
     By employing the crowned splines  119  in the interface between the valve shaft  110  and the drive shaft  115  in the EGR  102 , misalignment between the valve shaft  110  and the actuator  106 , such as the rack  114  or pinion  112 , is accommodated without increasing force on portions of the spline  119  that would otherwise prematurely wear the splines  119 . In addition, the crowned splines  119  can be configured to accommodate manufacturing tolerances in the housing  124 , the actuator  106  as well as the butterfly valve assembly  104 . 
     The engaging surface, such as carried by the sleeve, is configured to provide corresponding crowned splines  119  with a length of approximately 0.812 inches or 13/16 inches. 
     The invention has been described in detail with particular reference to a presently preferred embodiment, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.