BACKGROUND

[0001] This disclosure relates to compact configurations for combining a pump stage with a motor.

[0002] Compact motor-driven pumps are commonly employed to deliver fuel, lubricants, hydraulic or other fluids in equipment, land and water vehicles and aircraft. The pumps and motors are commonly manufactured separately and then assembled into the same housing, which may also serve as a conduit for fluid being pumped. The fluid being pumped may circulate through the motor to lubricate and cool the motor and electronics associated with a brushless motor configuration.

[0003] Roller vane, gerotor and turbine pump stages are commonly employed in such assemblies, with the pump stage selected based on the characteristics of the fluid being pumped and the pressure and volume of fluid flow required by the system. In the case of roller vane and gerotor pump designs, the pump stage typically includes three components that define a pumping chamber. An inlet plate defines one or more arcuate inlet ports for fluid to enter the pumping chamber and defines one axial side of the pumping chamber. An outlet plate defines one or more arcuate outlet ports and defines the opposite axial side of the pumping chamber. A retainer ring is sandwiched between the inlet and outlet plates and defines the radial, inside surface of the pumping chamber. In roller vane and gerotor pumps, the inside surface of the pumping chamber is defined by a circle eccentric from the center (rotational) axis of the motor and pump. The position of the inlet and outlet ports, in combination with eccentrically rotating roller vane or gerotor pump components, result in differential pressures in the pump chamber that force fluid through the pump from the inlet to the outlet. Pumped fluid may be directed through the motor for the purpose of cooling and lubrication. [0004] With respect to gerotor pumps in particular, the geometry and alignment of pump components is critical to smooth and reliable pump operation. One important relationship is the rotational axis of the inner gerotor and rotational axis of the motor shaft, which are preferably concentric (as close to the same axis as possible). Most gerotor pumps employ separately manufactured inlet and outlet plates axially spaced by the retainer ring. Separately manufactured parts must be tightly tolerance to prevent tolerance stack up issues that will interfere with proper gerotor pump operation. Further, the separate components must be carefully aligned during assembly to ensure a concentric relationship between the motor shaft, the inner gerotor and the eccentric path of the outer gerotor. Alignment is typically accomplished by pins or fasteners extending axially through the inlet plate, retainer ring, and outlet plate. Other unique assembly methods may be employed to ensure correct alignment of the several components. The inner gerotor may be centered on a bushing pin supported by one of the inlet or outlet plates. Alternatively, the inner gerotor may be supported by the motor shaft itself, depending upon the size of the motor shaft. Separately manufactured components with alignment structures may complicate manufacturing, assembly, and increase costs and have a potentially negative impact on reliability.

SUMMARY

[0005] An integrated motor-driven pump is proposed that reduces the part count of the assembly and addresses several tolerance and alignment issues by combining the outlet plate and retainer ring of the pump into a single component. The integrated motor-driven pump may also include an axial bushing for support of the motor shaft and inner gerotor, ensuring concentric rotation of these components. Combining one of the inlet or outlet plates with the retainer ring and including a central bushing eliminates the need for alignment pins and complex assembly procedures. The disclosure also combines one of the motor end plates with the disclosed integrated pump inlet or outlet plate, retainer ring and central bushing, eliminating the need for a separate motor end plate and bushing to support the motor shaft. [0006] The disclosed motor-driven pump preferably employs a brushless motor configuration and directs pumped fluid through the motor for cooling and lubrication. Pumped fluid may also be directed to cool the control electronics which drive the brushless motor, directly or indirectly. The motor end plate is formed as a single component with one of the pump inlet or outlet plates, and incorporates the retainer ring and a central bushing to support both the motor shaft and inner gerotor. The pump stage may include as few as three components; the inner gerotor, outer gerotor and one plate of the pump (typically the inlet plate, which may alternatively be referred to as the inlet manifold.

[0007] In one embodiment, a motor end plate is adapted to serve as the inlet or outlet plate of a pump secured to an axial end of the motor driving the pump.

[0008] In one embodiment, a motor end plate is integrated with an inlet or outlet plate of a pump, a guide ring of the pump and bushings to support the motor shaft and rotating pump parts.

[0009] Alternative embodiments of the disclosed integrated motor pump may incorporate one or more of the disclosed features and relationships included in the detailed description below.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a partially exploded view of a first embodiment of a gerotor pump partially integrated with an electric motor; and

[0012] Figure 2 is a sectional view through the gerotor pump partially integrated with an electric motor as shown in Figure 1 ;

[0013] Figure 3 is a second embodiment of a gerotor pump integrated with an electric motor;

[0014] Figure 4 is a sectional view through the gerotor pump integrated with an electric motor as shown in Figure 3, and [0015] Figures 5 and 6 are perspective views of the combined motor end plate, pump outlet plate, central bushing and pump retainer ring of the embodiment shown in Figures 3 and 4.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0016] A first embodiment of a gerotor pump 10 partially integrated with its drive motor 20 is illustrated in Figures 1 and 2. A second embodiment of a gerotor pump 1 10 integrated with its drive motor 120 is illustrated in Figures 3-6. Both embodiments are compatible with brushed or brushless DC motors, where the motor is assembled into a cylindrical housing and includes motor end plates spanning each longitudinal end of the housing. The motor end plates typically include bushings for supporting the motor shaft and openings to allow fluid being pumped to pass through the motor assembly between the rotor and stator and over the bushings to lubricate and cool the motor assembly during use.

[0017] Figure 1 illustrates an embodiment where an end plate 22 of the motor is formed as an outlet plate of the pump stage. This configuration eliminates the manufacture of a separate motor end plate in addition to the pump outlet plate. In the embodiment of Figure 1 , the motor end plate 22 includes at least one outlet port 24 configured to direct fluid from the gerotor set into the cylindrical motor housing 26, where fluid flows between the rotor 36 and stator 30, as well as over the bushings 32, 34 that support both ends of the motor shaft 28 (Depicted in Figure 2). The gerotor pump 10 also includes an inlet plate (or manifold) 12 with an inlet opening 15, a retainer ring 14, an outer gerotor 16, an inner gerotor 17, and a motor coupling 18. A pair of alignment pins 40 aid in aligning the retainer ring 14 with the inlet and outlet plates 12, 22, in turn also providing alignment between the inner gerotor 17 and motor shaft 28. A bushing 13 seated in the inlet plate 12 supports the inner gerotor 17 for rotation within the pumping chamber. The retainer ring inner surface 19 supports the outer geroter 16. The retainer ring inner surface 19 defines a circle that is eccentric to the axis of motor shaft rotation and the outside surface of bushing 13. Fasteners 42 secure the pump stage 10 to the motor end plate/outlet plate (or manifold) 12. [0018] The disclosed combined motor end plate/outlet manifold 22 is constructed of materials and surface properties compatible with its function as a working surface of a gerotor pump 10. The material must be resistant to wear and begin with a planar (flat) surface that will cooperate with adjacent surfaces of the gerotor set to define differential pressure zones within the pump 10. Suitable materials include steel or alloy that is cast or machined and finished to the correct dimensions. Powdered metallurgy may also be employed to form parts such as the combined motor end plate/outlet manifold/retainer ring component 150 of the embodiment shown in Figures 5 and 6, as well as the inner and outer gerotors 16, 17, 1 16, 1 17. The steel or alloy may begin as sheet or bar stock, which is cut and finished by methods known in the art. Tolerance stack in both the axial and radial direction can impact gerotor operation, so forming several support surfaces on the same component should reduce tolerance variation and improve pump operation and reliability.

[0019] It will be observed that, in the embodiment of Figures 1 and 2, the motor shaft 28, inner gerotor 17, and outer gerotor 16 are supported for rotation by different components, making it more challenging to ensure that the motor shaft 28 and inner gerotor 17 are truly concentric, and the proper eccentric is provided to guide rotation of the outer gerotor 16. In the embodiment of Figures 1 and 2, the motor coupling 18 is designed to allow for some misalignment of the motor shaft 28 with the axis of rotation of the inner gerotor 17. While the embodiment of Figure 1 does reduce part count relative to some prior art configurations, further improvements may be possible.

[0020] The embodiment of Figures 3 - 6 integrates the retainer ring with the pump outlet plate and arranges the combined structure 150 to serve as one of the motor end plates. As best shown in Figure 4, the center of the combined retainer ring and outlet plate includes a radially inside surface 152 that locates a bushing to support the motor shaft 128. The center of the combined retainer ring and outlet plate 150 also includes a boss 154 having a radially outside surface 156 that is arranged to support the inner gerotor 1 17. The same structure supports both the motor shaft 128 and inner gerotor 1 17. The motor shaft 128 extends through the center of the combined retainer ring and outlet plate 150 to engage the inner gerotor 1 17 and apply rotational force to the gerotor set during operation. The integral retainer ring inside surface 1 19 defines a circle that is eccentric relative to the axis of motor shaft rotation and the outside surface 156 of the center boss 154 which defines the axis of rotation of the inner gerotor 1 17. Rotation of the gerotor set within the integral retainer ring 150 produces differential pressures that draw fluid in through the inlet openings 1 15 in the inlet plate 1 12 and force fluid out through the outlet openings 124 in the outlet plate integral to the retainer ring 150. In the depicted embodiment, the integral retainer ring outside surface 151 radially accommodates the cylindrical motor housing 126.

[0021] Comparison of Figures 1 and 3 show the dramatic reduction in part count of the second embodiment of Figures 3 - 6 relative to the first embodiment of Figure 1 . The integral retainer ring 150 and central boss 154 that supports both the motor shaft 128 and the inner gerotor 1 17 reduce the parts necessary to ensure concentricity of rotation for the pump components relative to the motor shaft 128. Precise positioning of the pump and motor components ensures smooth and reliable operation of the motor driven pump.

[0022] The disclosed concept for integrating a compact pump with an electric motor is discussed in the context of a gerotor pump, but is not limited to only this pump configuration. Other compact pump configurations employ an eccentric surface to guide pump components or to direct fluid flow through the pump and may advantageously employ the disclosed concepts. Such pumps include, but are not limited to vane and roller vane pumps.