EP4698769A1 - Electric egr pump - Google Patents

Abstract

An exhaust gas recirculation system for an internal combustion engine that includes an electric motor and an exhaust gas recirculation pump coupled to the electric motor. The exhaust gas recirculation pump includes a housing defining an internal volume, with rotors disposed within the internal volume and connected to the electric motor. A bearing plate is attached to the housing wherein the bearing plate and an outer cover attached to the bearing plate define an oil cavity for lubrication of various parts of a transmission assembly. The housing includes a coolant flow path to reduce heat transfer from the exhaust gas recirculation pump to the electric motor.

Description

ELECTRIC EGR PUMP

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Indian Provisional Patent Application Serial No. 202311028988, filed April 21, 2023, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Increasing awareness of environmental considerations of vehicle exhaust gas and increasingly stringent exhaust regulations are driving vehicle produces and consumers alike to desire automotive vehicles that produce fewer harmful exhaust gasses. Many automotive vehicles that utilize internal combustion engines (for example, diesel, gasoline, or two stroke engines) include exhaust gas recirculation (EGR) to recirculate exhaust gas into the engine for mixture with the cylinder charge. The EGR gas that is intermixed with the air and fuel to the engine enhances the overall combustion of the fuel. This may reduce exhaust gas emissions. By including a separate EGR pump, an increase in fuel economy may be achieved in comparison to prior art systems that may use a turbocharger to drive an EGR flow with the addition of costly EGR valves. Additionally, a separate EGR pump provides full authority of the EGR flow rate. In a diesel application, a separate EGR pump may allow for removal of an EGR valve and replace a complicated variable geometry turbocharger with a fixed geometry turbocharger optimized for providing a boosted air charge. The separate EGR pump may provide reduced engine pumping work and improved fuel economy.

[0003] However, intermixing exhaust gas that contains particulate matter such as soot and/or water vapor (as a result of the combustion process of fuel supplied to the engine) into the engine intake manifold may cause soot deposits to accumulate on various engine components, leading to a degradation in performance.

SUMMARY OF THE INVENTION

[0004] The present disclosure relates to an improved exhaust gas recirculation (EGR) system which, as described herein, receives exhaust gas from an engine system (through an intercooler, in some examples) and recirculates it to the engine. In some examples, EGR system includes channels for coolant flow. In some examples, EGR system includes channels and a cavity for oil flow and retention.

[0005] Accordingly, the present application describes an exhaust gas recirculation system for an internal combustion engine comprising: an electric motor disposed within an electric motor housing; an exhaust gas recirculation pump coupled to the electric motor, the exhaust gas recirculation pump including a pump housing defining an internal volume; a plurality of rotors disposed within the internal volume, wherein a first rotor of the plurality of rotors is connected to the electric motor; a transmission assembly including a drive gear attached to the first rotor, the transmission assembly including a driven gear meshed with the drive gear, the driven gear coupled to a second rotor of the plurality of rotors, wherein the transmission assembly is positioned on an opposing side of the pump housing relative to the electric motor; a lip seal disposed around and in contact with a circumference of a rotor shaft, wherein the rotor shaft is integral to either the first rotor or the second rotor; and a pair of piston ring seals disposed around and in contact with a circumference of the rotor shaft, wherein the lip seal is located between a first set of bearings and the pair of piston ring seals, and wherein the first set of bearings is located between a gear and the lip seal.

[0006] In an aspect, the exhaust gas recirculation system further comprises a coolant flow path at least partially defined by the pump housing, the coolant flow path being defined around at least a second set of bearings.

[0007] In an aspect, the pump housing defines fin structures within the coolant flow path.

[0008] In an aspect, the fins structures are formed radially about the second set of bearings.

[0009] In an aspect, the exhaust gas recirculation system further comprises: a motor mounting adapter; a coolant inlet formed in the motor mounting adapter; and a coolant outlet formed in the adapter, the coolant inlet and the coolant outlet being configured for introducing coolant and at least partially defining a flow path for the coolant.

[0010] In an aspect, the exhaust gas recirculation system further comprises a bearing plate attached to the pump housing, the bearing plate including journals formed therein receiving the first set of bearings.

[0011] In an aspect, the bearing plate and an outer cover attached to the bearing plate define an oil cavity. [0012] In an aspect, the transmission assembly is positioned within the oil cavity.

[0013] In an aspect, the bearing plate includes at least one oil inlet extending to at least one oil outlet, the at least one oil outlet being defined by the outer cover, and wherein oil lubricates the second set of bearings and the transmission assembly.

[0014] In an aspect, the oil outlet is situated to allow for gravity draining of oil from the oil cavity.

[0015] In an aspect, the exhaust gas recirculation system further comprises: a shelf defined by the pump housing; a pocket defined at least by the shelf, a second bearing assembly, a motor mounting adapter, and an electric motor shaft; and a biasing element disposed within the pocket and encircling the electric motor shaft.

[0016] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting and non-exhaustive examples are described with reference to the following Figures.

[0018] Figure 1 is a perspective view of an EGR pump system, according to an example.

[0019] Figure 2 is a front exploded view of the EGR pump system of Figure 1, according to an example.

[0020] Figure 3 is a rear exploded view of the EGR pump system of Figure 1, according to an example.

[0021] Figure 4 is a perspective view of an EGR pump, according to an example.

[0022] Figure 5 is a perspective view of an EGR pump with an outer cover of a transmission assembly removed, according to an example.

[0023] Figure 6A is a front view of an EGR pump with an outer cover of a transmission assembly removed, according to an example.

[0024] Figure 6B is a front view of an EGR pump with an outer cover of a transmission assembly removed and a gear removed, according to an example. [0025] Figure 7 is a botom rear perspective view of an EGR pump with a motor mounting adapter removed, according to an example.

[0026] Figure 8 is a top rear perspective view of an EGR pump with a motor mounting adapter removed, according to an example.

[0027] Figure 9 is a rear view of an EGR pump with a motor mounting adapter removed, depicting a coolant fluid flow path, according to an example.

[0028] Figure 10 is a rear perspective view of a motor mounting adapter for an EGR pump and electric motor, according to an example.

[0029] Figure 11 is a front perspective view of a motor mounting adapter for an EGR pump and electric motor, according to an example.

[0030] Figure 12 is a rear perspective view of a portion of the EGR pump system of Figure 1, including the EGR pump and a portion of the electric motor, according to an example.

[0031] Figure 13 is a front perspective view of a portion of the EGR pump system of Figure 1, including the electric motor and a coolant seal plate, according to an example.

[0032] Figure 14 is a front perspective view of a portion of the EGR pump system of Figure 1, including the electric motor, according to an example.

[0033] Figure 15 is a horizontal cross-sectional view of the EGR pump system of Figure 1, according to an example.

[0034] Figure 16 is a portion of the horizontal cross-sectional view of the EGR pump system of FIGURE 15, according to an example.

[0035] Figure 17 is a portion of the horizontal cross-sectional view of the EGR pump system of FIGURE 15, according to an example.

[0036] Figure 18 is a vertical cross-sectional view of the EGR pump system of Figure 1, according to an example.

DETAILED DESCRIPTION

[0037] In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustrations specific embodiments or examples. These aspects may be combined, other aspects may be utilized, and structural changes may be made without departing from the present disclosure. Examples may be practiced as methods, systems, or devices. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.

[0038] Automotive vehicles that utilize internal combustion engines may include exhaust gas recirculation (EGR) to recirculate exhaust gas into the engine for mixture with the cylinder charge. The EGR gas that is intermixed with the air and fuel to the engine enhances the overall combustion of the fuel. The intermixing with the EGR gas with the air and fuel to the engine helps to control the maximum temperature of combustion of the fuel within the engine, which can reduce exhaust gas emissions. By including a separate EGR pump, an increase in fuel economy may be achieved in comparison to prior art systems that may use a turbocharger to drive an EGR flow with the addition of costly EGR valves. Additionally, a separate EGR pump provides full authority of the EGR flow rate. In a diesel application, a separate EGR pump may allow for removal of an EGR valve and replace a complicated variable geometry turbocharger with a fixed geometry turbocharger optimized for providing a boosted air charge. The separate EGR pump may provide reduced engine pumping work and improved fuel economy.

[0039] However, intermixing exhaust gas that contains particulate matter such as soot and/or water vapor (as a result of the combustion process of fuel supplied to the engine) into the engine intake manifold may cause soot deposits to accumulate on various engine components, leading to a degradation in performance. Water vapor is often expelled to the environment through an exhaust system. However, in a system utilizing an EGR pump, some water vapor included in the exhaust may be recirculated to the engine intake manifold. The water vapor may provide a carrier for exhaust particulate matter such as soot. Soot deposits may accumulate on various components, degrading performance.

[0040] Various portions of EGR pumps as disclosed herein may be exposed to exhaust gases at elevated temperatures. For example, the rotors within the pump may contact exhaust gases at temperatures such as from about 220° to 300° C. In such a scenario, the high temperature may demagnetize the components of the electric motor causing a loss of torque. Additionally, the high temperature may adversely affect the mechanical components of the EGR pump such as varying the heat treatments and properties of the materials. [0041] The present disclosure relates to an improved exhaust gas recirculation (EGR) system which, as described herein, receives exhaust has from an engine system and recirculates it to the engine. In some examples, EGR system includes channels for coolant flow (to reduce heat transfer from the EGR pump rotors to the electric motor that drives the EGR pump, such that the motor does not overheat). In some examples, EGR system includes channels and a cavity for oil flow and retention (to lubricate the various components of the EGR pump for safe and long operation in an EGR system environment). In some examples the disclosed EGR pump resists accumulation of soot deposits.

[0042] The EGR pump system described herein may deliver exhaust gas from an engine’s exhaust manifold to its intake manifold at a controlled, variable rate. In order to pump exhaust gas, the EGR system may use an EGR pump coupled to an electric motor. The electric motor may provide control of EGR flow rate by managing the motor speed and in turn, the pump speed and flow rate of exhaust gas.

[0043] These and other examples will be explained in more detail below with respect to Figures 1-18.

[0044] In accordance with principles of this disclosure, the Figures depict an example exhaust gas recirculation pump (EGR pump) system 10. The EGR pump system 10 includes an electric motor 12 that includes various motor components within a motor housing 13. In some examples, the electric motor 12 may be a brushless DC motor. In other examples, electric motor 12 may be another suitable type of electric motor.

[0045] An EGR pump (which may also be configured as a Roots-type device) 14 is coupled to the electric motor 12. The EGR pump 14 includes a pump housing 16 that defines an internal volume 17. Rotors 18 are disposed in the internal volume and are connected (at a first end of a rotor shaft 82) to the electric motor 12 (at an end of an electric motor shaft 84).

[0046] In some examples, pump housing 16 and other components disclosed herein that attach to the pump housing 16 may be made of ductile iron. In other examples, pump housing 16 and other components disclosed herein that attach to the pump housing 16 may be made of cast iron, steel alloys, non-alloyed steel, stainless steel, brass, other metals or metal alloys, or other materials. In some examples, rotors 18 may be made of ductile iron, cast iron, steel alloys, non-alloyed steel, stainless steel, brass, other metals or metal alloys, or other material. In some examples, rotors 18 may be coated with a coating that is appropriate for the EGR system 100 environment. In some examples, such a coating may be polymer or metal based. In some examples, various components of EGR pump system 10 may be formed by casting. In some examples, various components of EGR pump system 10 may be formed by machining.

[0047] In one aspect, the EGR pump system may be horizontally orientated (as in the particular example shown in the Figures) with the electric motor 12 positioned horizontally adjacent to the EGR pump 14. In one aspect, the EGR pump system may be vertically orientated with the electric motor 12 positioned vertically above the EGR pump 14 and rotors 18. In an aspect, the electric motor 12 may be positioned opposite a transmission assembly 50 of the EGR pump 14.

[0048] The exhaust gas recirculation pump system 10 includes a pump housing 16 that defines an internal volume 17 that encloses the rotors 18. Although different numbers of rotors 18 may be contemplated, the example shown in the figures includes two rotors (one pair) 18. Each rotor includes a plurality of lobes 19 that protrude radially outward from and extend longitudinally along a rotor shaft 82, 83. Although different numbers of lobes 19 may be contemplated, the example shown in the figures includes three lobes 19 on each of the rotors 18.

[0049] The pump housing 16 may be of shape configured to accommodate the lobes 19 of the rotors 18 (in some examples, substantially elliptical, rectangular, or cylindrical). The pump housing 16 includes a housing end face 20 linked with a housing sidewall 22. The portion of the housing 24 opposite the end 20 face is open.

[0050] In an example, EGR gas enters pump housing 16 via a gas inlet 60 and exits pump housing 16 via a gas outlet 62. In some examples, gas inlet 60 and gas outlet 62 may be of the same of different shapes. In the particular example shown, gas inlet 60 and gas outlet 62 are shaped as rectangles with rounded comers, although other shapes may be contemplated, including circular, oval, elliptical, square, rectangular, or other suitable shapes. In some examples, gas inlet 60 and gas outlet 62 are symmetrically shaped, allowing for gas adapters, pipes, or other features to be attached in varying orientations. In some examples, gas inlet 60 and gas outlet 62 are located symmetrically on the pump housing 16. In some examples, the path for gas to flow from internal volume 17 through gas inlet 60 and/or gas outlet 62 includes a curved portion and a linear straight section. In some examples, this linear straight section of gas inlet 60 and gas outlet 62 is parallel to oil outlet 48.

[0051] In some examples, an EGR gas outlet adapter may be attached to the pump housing 16 for routing EGR gases exiting the EGR pump 14 from gas outlet 62. In an aspect, the outlet adapter may be modular such that various shapes can be attached to the EGR pump 14 for different system configurations. The gas inlet 60 and gas outlet 62 may be reversed in some configurations, so that the same volume of EGR gas may flow in either direction through the EGR pump 14 and the EGR 14 may achieve the same performance.

[0052] The electric motor 12 includes a motor housing 13 having coolant passages 26 formed therein. The coolant passages 26 provide heat protection, remove heat from the electric motor 12, and are coupled to a coolant path. Coolant passages 26 may be of various shapes. Coolant passages 26 may be separated, in some examples, by spokes or separators 49. The coolant path may be linked with an engine-cooling path such as coolant from an engine radiator. The coolant enters at the coolant inlet 31 and cools an inverter associated with the electric motor 12. Coolant seals 61 are provided to contain the coolant.

[0053] The electric motor 12 includes a coolant plate 29 attached, connected, or fastened to the electric motor housing at a motor-facing surface 32 and connected to the pump housing 16 (via the motor mounting adapter 27) at a pump-facing surface 34. The coolant plate 29 includes a coolant inlet and outlet 31, 33. Coolant inlet and outlet 31, 33 of the coolant plate 29 align with coolant inlet and outlet 46, 47, respectively, of the electric motor 12.

[0054] In an aspect, an electric motor shaft 84 interfaces with a first end of a drive rotor shaft 82 that extends along an axis X. The drive rotor shaft 82 carries and turns a first rotor 18.

[0055] In one aspect, electric motor shaft 84 includes a pair of separated extending wedges 86. The drive rotor shaft 82 includes pair of separated extending wedges 92 that extend from its end. A connector 94 links the motor extending wedges 86 and rotor extending wedges 92. The connector 94 includes a central circular body 96 having wedge-shaped bodies 98 formed radially about a perimeter. The wedge-shaped bodies 98 define openings into which the extending wedges 86, 92 are positioned to couple the drive rotor shaft 82 and electric motor shaft 84. [0056] In some examples, connector 94 forms at least part of an insulated coupling that prevents heat transfer from the rotors 18 and drive rotor shaft 82 to the electric motor shaft 84 and electric motor 12. In an aspect, the insulated coupling may include a polymer material such as polyimide which may include reinforcing materials such as carbon fiber or glass fibers.

[0057] In an aspect, the EGR pump 14 includes bearings 28 to assist rotation of the rotor shafts 82, 83. These bearings 28 may require or benefit from lubrication, for example, from oil. In some examples, the bearings 28 may be sealed grease bearings that do not need an external source of oil lubricant and may eliminate potential oil blowby into the rotor cavity. In some examples, the bearings 28 may be ball bearings or another suitable type of bearing.

[0058] In some examples, the pump housing 16 may include an extended shelf 21 that extends toward the electric motor 12 past the rearmost edge of the assembly for bearings 28. This shelf 21 defines a pocket 23 that accommodates a biasing element 25. In some examples, biasing element 25 may be a type of spring. In some examples, the biasing element(s) 25 circumscribe(s) the external perimeter of the rotor shafts 82, 83. In some examples, biasing element 25 may contact the bearing assembly for bearings 28 on a first face, and the motor mounting adapter 27 on a second face.

[0059] In some examples, the rotor shafts 82, 83 include a circumscribing groove that includes a pair of piston ring seals 35, to prevent movement of coolant and/or oil between the electric motor 12 and the internal volume 17 of the EGR pump 14.

[0060] In some examples, the pump housing 16 defines a coolant channel 69 that defines at least a portion of a coolant flow path (CFP) at pump housing end face 20. In some examples, the coolant channel 69 includes fin structures 70 formed thereon. The fin structures 70 increase the surface area for contact between the material of the pump housing 16 with the coolant to increase extraction of heat from the pump housing 16 due to the hot EGR gas in the EGR pump 14. The fin structures 70 also increase turbulent mixing of the coolant, thereby also increasing the heat transfer from the pump housing 16. The fin structures 70 may be formed in various patterns about the bearings 38. In some examples, as depicted, the fin structures 70 are dispersed radially about the bearings 38. In some examples, the fins 70 are formed about the bearings 38 and perpendicular to the bearings 38. In some examples, additional fins 70 are also formed on the pump housing 16 extending towards the bearings 38. In some examples, coolant channel 69 also includes one or more diversion structures 71, to guide the flow of the coolant fluid along the CFP. In some examples, a separator 75 divides one portion of coolant channel 69 so that the CFP forms a beginning point and an endpoint, so that the coolant may be directed from one beginning point to an endpoint in a desired CFP through the coolant channel 69.

[0061] As the drive rotor shaft 82, it turns a drive gear 52 that is part of transmission assembly 50. Drive gear 52 is meshed with driven gear 54, which rotates with a driven rotor shaft 83 (that extends along an axis Y) at a first end.

[0062] The exhaust gas recirculation pump system 10 includes a bearing plate 36 attached to the pump housing 16 at the open end 24. In some examples, the bearing plate 36 includes journals 37 that receive bearings 38. The bearing plate 36 and outer cover 40 define an oil cavity 42. Various shaped outer covers 40 may be utilized, in some examples.

[0063] The EGR pump system 10 includes the transmission assembly 50 that includes drive gear 52 that is meshed with driven gear 54. The drive gear 52 is coupled to the drive rotor shaft 82. The driven gear 54 is meshed with the drive gear 52 and is coupled to the driven rotor shaft 83. In an aspect, the transmission assembly 50 is positioned on an opposing side of the pump housing 16 relative to the electric motor 12 and within the oil cavity 42.

[0064] In some examples, a snap ring 53 is located around the circumference of each of rotor shafts 82, 83 behind the gears 52, 54 to prevent lateral movement of the bearings 38 and transmission 50. A transmission retainer plate may be provided in some examples, about the bearings 38 and attached to the bearing plate 36 to prevent lateral movement of the bearings 38 and transmission 50.

[0065] Oil (for example, from an engine or other source) enters via an oil inlet 44 and into the oil cavity 42 for lubricating and cooling the bearings 38 and transmission 50. In some examples, oil inlet 44 may include a banjo type fitting, threaded connection, welded connection, quick-connect fitting, or other appropriate connection feature. In some examples, the bearings 38 (that assist in the rotation of rotor shafts 82, 83) may be open-type bearings that are lubricated by the oil. The oil exits the oil cavity 42 at a single oil outlet 48. In some examples, oil outlet 48 may be located in the center of the oil cavity at the bottom of the outer cover 40, and the bottom side of outer cover 40 may be sloped to funnel oil downward toward the oil outlet 48 so that oil may gravity drain from the oil cavity 42 when needed. In some examples, oil outlet 48 has a circular orifice. In some examples, oil outlet 48 may be located differently or be shaped differently (for example, if the EGR pump system is in a non-horizontal orientation), to allow for gravity draining of the oil from the oil cavity 42. Oil exiting oil outlet 48 may, in some examples, be routed to an engine crank case. Seals 57 are provided on the bearing plate 36 to seal the oil cavity 42.

[0066] Oil may be introduced into the transmission area using a variety of oil dispersing structures. In some examples, the oil dispersing structure may be an oil slot formed in the bearing plate 36. Oil may be moved through the slot and contact the drive gear 52 and driven gear 54 to lubricate the gears 52, 54 and the bearings 38.

[0067] In some examples, the oil dispersing structure may be an oil conduit 55 that is positioned at an upper or lower portion of the oil cavity 42 and formed in the bearing plate 36. The oil conduit may include holes 59 such that oil will be moved through the holes and contact the drive gear 52 and driven gear 54 to lubricate the gears 52, 54 and the bearings 38.

[0068] In some examples, to prevent oil from leaking from the oil cavity 52 and into the space defined by the pump housing 16, a series of leak prevention features may be installed. In some examples, closer to the bearings 38, a lip seal 85 is included that contacts the circumference of the rotor shaft 82, 83 at one, two, or more points. Closer to the lobes of the rotors 18, a groove 87 may house a pair of piston ring seals 89 that contacts the circumference of the rotor shaft 82, 83.

[0069] Driven rotor shaft 83 carries and turns a second rotor 18. At its second end, driven rotor shaft 83 is enclosed by a driven end interface 73 of a motor mounting adapter 27.

[0070] The EGR pump 14 includes a motor mounting adapter 27. Motor mounting adapter 27 includes a motor mounting section 65 that mounts on one side to the electric motor 12 and on the other side to the EGR pump 14. Motor mounting section 65 includes a drive opening 64 to accommodate passage of rotor shaft 82 and electric motor shaft 84. [0071] Motor mounting adapter includes an adjacent mounting section 66 that mounts to the EGR pump 14. Adjacent mounting section 66 includes driven end interface 73.

[0072] A coolant inlet and coolant outlet 67, 68 are formed in the motor mounting adapter 27 to introduce coolant into coolant cavity 42 and to define a flow path for the coolant. The coolant inlet and coolant outlet 67, 68 are formed to be open to opposing sides of the separator 75. The coolant inlet and outlet 67, 68 are defined by bores formed through the adapter 27. The bores may be formed at an angle such they are not perpendicular relative to the adapter 27. The coolant inlet and outlet 67, 68 correspond to and align with coolant inlet and outlet 31, 33, respectively.

[0073] For the purposes of this application, terms such as “upper,” “lower,”

“upward,” and “downward” are intended to be descriptive with reference to and in relation to the orientation shown in the Figures for clarity, but the examples as practiced and included in the scope of the claims may include examples where the systems and devices are in a different orientation.

[0074] While particular uses of the technology have been illustrated and discussed above, the disclosed technology can be used with a variety of environments in accordance with many examples of the technology. The above discussion is not meant to suggest that the disclosed technology is only suitable for implementation within the environments shown and described above. As should be appreciated, the various aspects described with respect to the figures herein are not intended to limit the technology to the particular aspects described. Accordingly, additional configurations can be used to practice the technology herein and/or some aspects described can be excluded without departing from the methods and systems disclosed herein.

[0075] This disclosure described some aspects of the present technology with reference to the accompanying drawings, in which only some of the possible aspects were shown. Other aspects can, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects were provided so that this disclosure was thorough and complete and fully conveyed the scope of the possible aspects to those skilled in the art.

[0076] Similarly, where operations of a process are disclosed, those operations are described for purposes of illustrating the present technology and are not intended to limit the disclosure to a particular sequence of operations. For example, the operations can be performed in differing order, two or more operations can be performed concurrently, additional operations can be performed, and disclosed operations can be excluded without departing from the present disclosure. Further, each operation can be accomplished via one or more sub-operations. The disclosed processes can be repeated. [0077] Although specific aspects were described herein, the scope of the technology is not limited to those specific aspects. One skilled in the art will recognize other aspects or improvements that are within the scope of the present technology. Therefore, the specific structure, acts, or operations are disclosed only as illustrative aspects. The scope of the technology is defined by the following claims and any equivalents therein.

Claims

What is claimed is:

1. An exhaust gas recirculation system for an internal combustion engine comprising: an electric motor disposed within an electric motor housing; an exhaust gas recirculation pump coupled to the electric motor, the exhaust gas recirculation pump including a pump housing defining an internal volume; a plurality of rotors disposed within the internal volume, wherein a first rotor of the plurality of rotors is connected to the electric motor; a transmission assembly including a drive gear attached to the first rotor, the transmission assembly including a driven gear meshed with the drive gear, the driven gear coupled to a second rotor of the plurality of rotors, wherein the transmission assembly is positioned on an opposing side of the pump housing relative to the electric motor; a lip seal disposed around and in contact with a circumference of a rotor shaft, wherein the rotor shaft is integral to either the first rotor or the second rotor; and a pair of piston ring seals disposed around and in contact with a circumference of the rotor shaft, wherein the lip seal is located between a first set of bearings and the pair of piston ring seals, and wherein the first set of bearings is located between a gear and the lip seal.

2. The exhaust gas recirculation system of claim 1, further comprising a coolant flow path at least partially defined by the pump housing, the coolant flow path being defined around at least a second set of bearings.

3. The exhaust gas recirculation system of claim 2 wherein the pump housing defines fin structures within the coolant flow path.

4. The exhaust gas recirculation system of claim 3 wherein the fins structures are formed radially about the second set of bearings.

5. The exhaust gas recirculation system of claim 2, further comprising: a motor mounting adapter; a coolant inlet formed in the motor mounting adapter; and a coolant outlet formed in the adapter, the coolant inlet and the coolant outlet being configured for introducing coolant and at least partially defining a flow path for the coolant.

6. The exhaust gas recirculation system of claim 1, further comprising a bearing plate attached to the pump housing, the bearing plate including journals formed therein receiving the first set of bearings.

7. The exhaust gas recirculation system of claim 6, wherein the bearing plate and an outer cover attached to the bearing plate define an oil cavity.

8. The exhaust gas recirculation system of claim 7, wherein the transmission assembly is positioned within the oil cavity.

9. The exhaust gas recirculation system of claim 7, wherein the bearing plate includes at least one oil inlet extending to at least one oil outlet, the at least one oil outlet being defined by the outer cover, and wherein oil lubricates a second set of bearings and the transmission assembly.

10. The exhaust gas recirculation system of claim 9, wherein the oil outlet is situated to allow for gravity draining of oil from the oil cavity.

11. The exhaust gas recirculation system of claim 1, further comprising: a shelf defined by the pump housing; a pocket defined at least by the shelf, a second bearing assembly, a motor mounting adapter, and an electric motor shaft; and a biasing element disposed within the pocket and encircling the electric motor shaft.