Electric machine rotor

An electric machine rotor includes a core, a first end plate, a second end plate, and a shaft. The core defines an internal cavity. The first and second end plates each define a central orifice and are respectively secured to opposing axial ends of the core. The shaft is disposed within the cavity and engages the first and second end plates within the central orifices to facilitate synchronized rotation of and torque transfer between the core and shaft.

TECHNICAL FIELD

The present disclosure relates to electric machines, including motors and/or generators.

BACKGROUND

Electric machines, including motors, generators, and combination motor/generators include a rotor that is configured to rotate within in a stator to convert electrical energy into rotational kinetic energy.

SUMMARY

An electric machine rotor includes a cylindrical core, end plates, and a shaft. The cylindrical core defines an internal cavity. The end plates define central orifices and are secured to opposing axial ends of the core. The shaft is disposed within the cavity, extends outward from the cavity through each orifice, and engages the orifices via interference-fits such that the end plates facilitate synchronized rotation of and torque transfer between the core and shaft.

An electric machine rotor includes a core, end plates, and a shaft. The core has inner and outer diameters. The inner diameter defines an internal cavity. The end plates define keyed orifices and are secured to opposing axial ends of the core between the inner and outer diameters. The shaft is disposed within the cavity, extends outward through each orifice, and has keyed sections that engage the keyed orifices such that the end plates facilitate torque transfer between the core and shaft.

An electric machine rotor includes a core, a first end plate, a second end plate, and a shaft. The core defines an internal cavity. The first and second end plates each define a central orifice and are respectively secured to opposing axial ends of the core. The shaft is disposed within the cavity and engages the first and second end plates within the central orifices to facilitate synchronized rotation of and torque transfer between the core and shaft.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a rotor10for an electric machine is illustrated. The electric machine may be an electric motor, an electric generator, or a combination motor/generator. The electric machine may be utilized in the powertrain of an electric or hybrid vehicle to provide propulsion power for the vehicle. The rotor10includes a cylindrical core12the defines an internal cavity14. More specifically, the core12includes an outer diameter16and an inner diameter18that defines the internal cavity14. The core12is comprised of a plurality of laminate plates20that are sequentially stacked in an axial direction along an axis of rotation22of the rotor10.

Referring toFIG. 3, a front view of the one of the laminate plates20is illustrated. The laminate plates20are individually fabricated from a material such iron or steel. Each laminate plate20includes an iron or steel plate24and a plurality of permanent magnets26that are secured to the iron or steel plate24. The laminate plates20are then aligned in an axial direction along the axis of rotation22to form the cylindrical core12. The iron or steel plates24may define through holes28that are configured to receive dowels or fasteners to properly align the plurality of laminate plates20to form the cylindrical core (seeFIGS. 1 and 2). The laminate plates20may be stacked “loose”, welded, or bonded together depending the desired application. The laminate plates20may include a thin layer of insulating material (e.g., a thin layer of epoxy that is approximately 0.001 mm thick). Although not depicted inFIGS. 1 and 2, there may be small spaces between adjacent laminate plates20at locations where the adjacent laminate plates20are not affixed to each other, if the application requires the adjacent laminate plates20to be affixed to each other (i.e., via welding or bonding).

Referring toFIGS. 1, 2, 4, and 5, end plates30(which may also be referred to as the first and second end plates) may be secured to opposing axial ends32of the core12between the inner diameter18and the outer diameter16of the core12. Securing the end plates30to the core12facilitates synchronized rotation and torque transfer between the end plates30and the core12. The end plates30may define fastening orifices34that are configured to align with the through holes28defined by the plurality of laminate plates20. Dowels36may be disposed within the fastening orifices34of the end plates30and the through holes28defined by the laminate plates20in order to secure the end plates30to the opposing axial ends32of the core12. Each dowel36may be disposed within one fastening orifice34defined by the first end plate30, within one through hole28defined by each of the laminate plates20, and within one fastening orifice defined by the second end plate30. More specifically, each dowel36may engage one fastening orifice34defined by the first end plate30via a clearance-fit (i.e., slip-fit), engage one through hole28defined by each of the laminate plates20via a clearance-fit, and engage one fastening orifice34defined by the second end plate30via an interference-fit (i.e., press-fit).

Alternatively, shoulder bolts38may disposed within the fastening orifices34of the end plates30and the through holes28defined by the laminate plates20in order to secure the end plates30to the opposing axial ends32of the core12. Each shoulder bolt38may be disposed within one fastening orifice34defined by the first end plate30, within one through hole28defined by each of the laminate plates20, and within one fastening orifice defined by the second end plate30. More specifically, each shoulder bolt38may engage one fastening orifice34defined by the first end plate30via a clearance-fit, engage one through hole28defined by each of the laminate plates20via a clearance-fit, and engage one fastening orifice34defined by the second end plate30via threads of the shoulder bolt38, wherein the fastening orifice34defined by the second end plate30is a tapped orifice. It should be noted that althoughFIG. 2depicts one dowel36and one shoulder bolt38, dowels alone, shoulder bolts alone, or any combination of dowels and shoulder bolts may be utilized to secure the end plates30to the core12.

The end plates30each define a central orifice40. A shaft42is disposed within the cavity14and engages each of the end plates30within the central orifices40in order to facilitate synchronized rotation of and torque transfer between the core12and the shaft42via the end plates30. In order to facilitate synchronized rotation of and torque transfer between the core12and the shaft42via the end plates30, the shaft42may engage at least one of the central orifices via an interference-fit44. The shaft42may extend outward from the cavity14through each central orifice40such that ends46of the shaft42are disposed on an exterior of the end plates30. The ends46of the shaft42may be secured to bearings (not shown) within a stator (not shown) of the electric machine in order to facilitate rotation of the rotor10.

The shaft42may include a shoulder48disposed on one end46that is configured to engage one of the end plates30. A retaining nut50may engage a threaded portion of the shaft42on an opposing end46of the shaft42relative to the shoulder48, and engage the other of the end plates30. The shoulder48and retaining nut50combination are configured to engage the end plates30to prevent axial movement of the shaft42relative to the end plates30and the core12. A retaining ring that engages a groove defined on the exterior of the shaft42may be utilized as opposed to the retaining nut50in order to engage the other of the end plates30and prevent axial movement of the shaft42in combination with the shoulder48.

The internal cavity14defined by the core12provides a space or gap between the shaft42and the core12(or more specifically the laminate plates20). The shaft42may define a fluid circuit52that is configured to deliver lubricating and/or cooling fluid from a fluid source (not shown) to the internal cavity14and directly onto the core12(or more specifically the laminate plates20) in order to cool the core12. More specifically, the lubricating and/or cooling fluid may flow across the inner diameter18of the core12within the cavity14in order to cool the core12. The lubricating and/or cooling fluid is then transferred out of the cavity14via fluid channels54defined by the end plates30. The fluid source may be a sump (not shown). A pump (not shown) may be configured to transfer the lubricating and/or cooling fluid out of the sump and into the fluid circuit52.

The rotor design of the current application (i.e., where a space or gap is provided between the shaft42and the core12) is advantageous due to the reduction of the weight of the core, which is the result of defining a space or gap between the shaft and the core as opposed to the core including additional material that occupies that space or gap. The rotor design of the current application is also advantageous due to the increased surface area along the inner diameter18of the core12which may be directly cooled via a lubricating and/or cooling fluid that flows out of the fluid circuit52defined by the shaft42and directly onto the core12.

Referring toFIGS. 4-6C, the end plates30may include a geometric feature where the end plates30protrude into the cavity14proximate the central orifices40such that an axial thickness56of the end plates30(i.e., the thickness of the end plates30in the axial direction along the axis of rotation22) proximate the central orifices40is greater than an axial thickness58of the end plates30proximate outer diameters60of the end plates30. Increasing the axial thickness of the end plates30proximate the central orifices40increases the interference area between the shaft42and the end plates30within the central orifices40. Increasing the interference area between the shaft42and the end plates30in turn increases the torque transfer capability between the shaft42and end plates30, and increases the stiffness of the end plates30which prevents or decreases the amount deformation of the end plates30at the regions of the end plates30proximate to the central orifices40.

FIGS. 6A-6Cillustrate alternative embodiments of the geometric feature where the end plates30protrude into the cavity14proximate the central orifices40such that the axial thickness of the end plates is increased proximate the central orifices40.FIG. 6Aillustrates a first embodiment where the geometric feature includes a tapered surface62that gradually increases the axial thickness of the end plates30from the axial thickness58proximate outer diameters60to the axial thickness56proximate the central orifices40.FIG. 6Billustrates a second embodiment where the geometric feature includes a stepped surface64that increases the axial thickness of the end plates30from the axial thickness58proximate outer diameters60to the axial thickness56proximate the central orifices40.FIG. 6Cillustrates a third embodiment where the geometric feature includes both a tapered surface62and a stepped surface64that each increase the axial thickness of the end plates30from the axial thickness58proximate outer diameters60to the axial thickness56proximate the central orifices40.

Referring toFIGS. 2, 4-5, and 7A-7C, the end plates30may include or define retaining features66that are configured to maintain the position of the core12relative to the end plates30. The retaining features66are protrusions that are disposed on the end plates30radially outward of the central orifices40. The retaining features66may be integral to the ends plates30. The retaining features66extend axially (i.e., in the axial direction along an axis of rotation22) from an internal surface of the end plates and into the cavity14. Specifically, the retaining features66may engage the inner diameter18of the core12to maintain the position the core12relative to the end plates30.

FIGS. 7A, 7B, and 7Cillustrate alternative embodiments of the retaining features, i.e., retaining features66,66′, and66″. Each retaining feature66,66′, and66″ includes a top or outer surface68that engages the inner diameter18of the core12to maintain position the core12relative to the end plates30. The retaining feature66depicted inFIG. 7Ahas a rectangular shaped cross-section, the retaining feature66′ depicted inFIG. 7Bhas a triangular shaped cross-section, and the retaining feature66″ depicted inFIG. 7Chas a trapezoidal shaped cross-section.

Referring toFIG. 8, a front view of an alternative embodiment of the end plates30′ is illustrated. The elements of the alternative embodiment of the end plates30′ depicted inFIG. 8that are common to elements of the end plates30depicted inFIGS. 1, 2, 4, and 5will have the same structure and functionally as described with respect to end plates30unless otherwise stated herein. The central orifice40′ of the alternative embodiment of the end plates30′ has a polygonal shape as opposed to the circular shape depicted inFIG. 4. The central orifice40′ depicted inFIG. 8may be referred to as a keyed orifice40′. The shaft42may include keyed sections70(SeeFIG. 2) that engage the keyed orifices40′ in order to facilitate synchronized rotation of and torque transfer between the core12and the shaft42via the end plates30′. The engagement between the keyed sections70and the keyed orifices40′ may be referred to as a keyed engagement. A keyed engagement is an engagement between a shaft, pin, bolt, wedge, or other component and a hole, slot, orifice, space, etc. that locks or holds two or more parts of a mechanism or structure together.

The keyed sections70may have cross-sectional areas that have polygonal shapes that match and mate with the polygonal shapes of the keyed orifices40′ in order to facilitate synchronized rotation of and torque transfer between the core12and the shaft42via the end plates30′. For example, if the keyed orifices40′ have square shapes, the keyed sections70will also have square shapes that are configured and sized to fit within the keyed orifices40′. Although the keyed sections70should be sized to fit within the keyed orifices40′, the keyed sections70should also be sized to engage the end plates30′ when rotated within the keyed orifices40′ to facilitate synchronized rotation between the shaft42and the end plates30′. The keyed sections70should not be size to freely rotate within the keyed orifices40′ once inserted therein. The keyed sections70may engage the keyed orifices40′ via interference-fits (i.e., press-fits) or clearance-fits (i.e., slip-fits). AlthoughFIG. 8illustrates the keyed orifices40′ as being square in shape, it should be understood that the they keyed orifices40′ and the keyed sections may have any matching polygonal shape such as, but not limited to, triangles, squares, rectangles, pentagons, hexagons, heptagons, octagons, nonagons, decagons, etc.