[0001] This application claims the benefit of United States Provisional

Application Serial No. 61/267,592 filed December 8, 2009.

TECHNICAL FIELD

[0002] The field to which the disclosure relates generally includes low pressure exhaust gas recirculation valves and engine breathing systems including the same.

BACKGROUND

[0003] Figure 1 is a schematic view of a prior modern diesel engine breathing system using a small stage turbocharger. Such a system may include a high pressure exhaust gas recirculation (EGR) loop 3and a low pressure EGR loop 10. Exhaust gases are generated by the engine 1 and exit through an exhaust gas manifold 2. The exhaust gas then passes through a turbine 4, the particulate filter 5 and then exits through the exhaust pipe 7.

[0004] To achieve low nitrogen oxide (NO _x ) emissions, part of the exhaust gas that is exiting the engine through the exhaust manifold 2 is redirected through the high pressure EGR-path 3, the EGR cooler 12 and the EGR valve 16 into the intake manifold 13. To create enough EGR-flow through the high pressure EGR path 3 the intake throttle valve 14 can be adjusted accordingly. If the high pressure EGR valve 16 is fully open and more flow through the high pressure EGR path 3 is required, the throttle valve 14 which is commonly a flapper valve, can be closed gradually.

[0005] Another way of reducing NO _x emissions is to apply a low

pressure EGR. Exhaust gases redirected from the exhaust side after the particulate filter 5 into a low pressure EGR path 10 to flow into the intake duct 9 before the compressor 13. The exhaust gas flows through a filter 8, a low pressure EGR cooler 1 1 and then is regulated by low pressure EGR valve 12. If the low pressure EGR valve 12 is fully open and more EGR gas flow is desired, the exhaust throttle 6 is closed accordingly to create sufficient back pressure. Instead of using exhaust throttle 6, an intake throttle 18 can be used to create sufficient suction pressure into the intake duct 9 downstream of the throttle valve 18 but upstream of the compressor 13. However, packaging an additional valve in front of the compressor is sometimes not possible. Furthermore, an additional throttle valve requires additional connections and precise control in the engine emissions control unit. Also, the additional actuator for such a valve is quite expensive due to onboard diagnostic requirements and other vehicle operating requirements.

SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0006] One exemplary embodiment includes the integration of an intake throttle device into a typical low pressure exhaust gas recirculation valve design.

[0007] Other exemplary embodiments of the invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while disclosing exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Exemplary embodiments of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0009] FIG. 1 is a schematic illustration of a single stage turbocharged diesel engine with a low pressure exhaust gas recirculation system utilizing exhaust throttle according to the prior art.

[0010] FIG. 2 is an illustration of a turbocharger for use in a low

pressure exhaust gas recirculation system utilizing an exhaust throttle valve.

[0011] FIG. 3 is an illustration of a turbocharger for use in a low

pressure EGR system utilizing a low pressure EGR control valve according to one exemplary embodiment.

[0012] FIGS. 4A-4B illustrate a low pressure EGR control valve

integrated into the turbocharger intake area of an engine breathing system according to one exemplary embodiment.

[0013] FIG. 5 is an illustration, including portions cut away, of a

combination valve using slot and key interconnection according to one exemplary embodiment.

[0014] FIG. 6 is a sectional view of a valve using a spring preload to achieve contact between the intake control flap and the EGR control flap according to one exemplary embodiment. [0015] FIG. 7 is a graph showing the opening characteristic (angle) of the intake control flap as a function of the EGR control flap rotational angle in a valve according to one exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0016] The following description of the embodiment(s) is merely exemplary (illustrative) in nature and is in no way intended to limit the invention, its application, or uses.

[0017] One embodiment includes a very cost effective low-pressure

EGR combination valve with the function to open the EGR path (EGR-control function) and at the same time being capable of purposely closing up to a significant portion of the projected flow area upstream of the compressor (intake flow control function) to maximize the EGR flow mass. In one embodiment the intake control flap is a simple add-on to a base EGR control valve and does not significantly influence the design or cost of the EGR control valve. An inner linkage (between the EGR control plate and the intake control valve plate) is designed to substantially be located inside the flow area. The linkage may be provided by connecting the EGR control valve plate via a key and slot to the intake control valve plate. In one embodiment, a spring acts on the intake control throttle plate, and is designed to maintain contact between the plates at all times.

[0018] In one embodiment, the intake linkage may be used to link the

EGR control valve plate to the intake air control plate in a way to achieve a desired open characteristics of the intake air control plate in relationship to the EGR control valve plate to realize an optimal EGR delivery characteristics at minimum intake pressure across the intake control valve plate.

[0019] In one embodiment, both flaps may be located in one valve housing 200, with the valve housing being connected directly, either using no gasket, an O-ring or a face seal, to the compressor inlet/mixing area. In one embobdiment, the valve housing may be attached to the mixing area so that the intake air control flap reaches substantially into the intake air stream when the EGR control flap is substantially open. The mixing area in front of the compressor may be constructed and arranged to accept the low pressure EGR combination valve in close proximity so that the flap of the low pressure EGR combination valve can swing into the mixer and substantially block the intake flow. The intake control flap may be constructed and arranged to have significant clearance of the housing of the mixer in the maximum intake throttling position. In one embodiment, the intake control flap may only block a maximum of 90 percent of the intake flow area.

[0020] As will be appreciated from FIGS. 4A-4B, one exemplary embodiment includes a combination valve integrated into the turbocharger intake area. The combination valve includes a first flapper valve 100 which pivots about an EGR valve shaft 102. The first flapper valve 100 is linked to a second flapper valve 104. The second flapper valve 104 is pivotally connected to the housing by a rod 106 and is biased by an intake flapper return spring 108. The second flapper valve 104 includes a slot 1 10 formed therein. The first flapper valve 100 includes a post or key 1 12 on the back face thereof constructed and arranged to be received in the slot 1 10 of the second valve 104. As the first valve 100 is pivoted to open the passage to allow exhaust gas recirculation air to flow from the exhaust side of an engine breathing system to the compressor wheel, the key or post 1 12 forces the second flapper valve 104 into a position which at least partially obstructs the flow of incoming air from the air cleaner and reduces the air pressure in the conduit leading to the compressor wheel so that an increased amount of exhaust gas may flow from the exhaust side into the compressor wheel. The slot 1 10 formed in the second flapper valve 104 may extend in a generally arcuate path or have a generally arcuate shaped configuration. The slot 1 10, post or key 1 12, or the linkage between the first flapper valve 100 and the second flapper valve 102 may be constructed and arranged to provide lost motion if desired.

The above description of embodiments of the invention is merely exemplary in nature and, thus, variations thereof are not to be regarded as a departure from the spirit and scope of the invention.