Patent ID: 12253153

DETAILED DESCRIPTION

A battery electric vehicle (BEV) can include an electric motor directly coupled to a differential that uses face gears to drive a plurality of wheels of the BEV. The differential can be coupled in a way that it is substantially coaxial with an output shaft of the electric motor. One or more gearsets are coupled between an output of the differential and a driven wheel of the BEV such that a gear ratio between the wheel and the output of the differential permits loads within face gear rated load values. In one example, the gear ratio between an output shaft of the rotating electrical machine and the drive wheel can be eight to one or greater.

Turning toFIG.1, an implementation of a battery electric vehicle (BEV) is shown. The BEV10can detachably couple to an electrical grid12and can receive electrical power from the grid12. The electrical grid12can include any one of a number of electrical power generators and electrical delivery mechanisms. Electrical generators (not shown) create AC electrical power that can then be transmitted a significant distance away from the electrical generator for residential and commercial use. The electrical generator can couple with the electrical grid12that transmits the AC electrical power from the electrical generator to an end user, such as a residence or a business.

The BEV10includes an electric drive system14including one or more rotating electrical machines (also referred to as electric motors) that have a stator with stator windings and a rotor that can be angularly displaced relative to the stator (not shown). The rotor can be coupled with a differential that may be concentrically positioned with respect to the rotor, such that an outer surface of the differential is concentrically received by a radially-inwardly-facing surface of the rotor. In one implementation, the rotating electrical machine is a permanent magnet synchronous electrical machine, which includes a rotor having a plurality of angularly-spaced permanent magnets. The permanent magnets can be made from any one of a number of different materials, one example of which is a neodymium alloy or other rare earth element. The electric drive system14can also include a differential and one or more transmissions, as will be described below in greater detail. The stator windings can receive electrical current the supply of which can be regulated by a control system16that induces the angular displacement of the rotor relative to the stator. The control system16can include an array of power control electronics and microprocessors that facilitate the operation of the rotating electrical machine16. These electronics may include an inverter implemented using a plurality of MOSFETs that switch on and off according to a choreographed order and timing at the direction of a motor controller to induce rotor angular movement. The control system16can output current commands that regulate the electrical current supplied from a vehicle battery20to the rotating electrical machine14. The current commands can be implemented using one or more microprocessors having input/output and non-volatile memory where data can be stored and accessed. The control system16can also include a DC-DC converter to regulate voltage levels of electrical power supplied to the electrical machine14.

BEV service equipment (not shown), also referred to as a BEV charging station, can receive AC electrical power from the grid12and provide the electrical power to the BEV10. An electrical cable18can detachably connect with an electrical receptacle on the BEV10and electrically link a BEV charging station with the vehicle battery20so that AC electrical power can be communicated between the charging station, rectified into DC electrical power, and then used to charge the vehicle battery20. The BEV charging station can be classified as “Level 2” BEV service equipment that receives 240 VAC from the grid12and supplies 240 VAC to the BEV10such that the AC electrical power is rectified at the BEV10. It is possible the level of AC electrical power input to a charging station and/or the level of AC electrical power output from a charging station is different in other implementations.

The term “battery electric vehicle” or “BEV” can refer to vehicles that are propelled, either wholly or partially, by rotating electrical machines or motors. BEV can refer to electric vehicles, plug-in electric vehicles, hybrid-electric vehicles, and battery-powered vehicles. The vehicle battery20can supply DC electrical power, that has been converted from AC electrical power, to the electrical machine(s)14that propel the BEV10. As noted above, the control system16can convert the DC electrical power into AC electrical power to induce angular movement of the rotor relative to the stator. The vehicle battery20or batteries are rechargeable and can include lead-acid, nickel cadmium (NiCd), nickel metal hydride, lithium-ion, and lithium polymer batteries, to name a few. A typical BEV battery voltage is 200 to 800 VDC. The term “electric drive system” can include not only the electric motor but also the inverter, the vehicle battery, and other electrical components of the BEV.

FIG.2depicts an implementation of the electrical drive system14used in the BEV10. The electrical drive system14can include a rotating electrical machine22, a differential24, and reduction gearboxes26coupled to the differential24and the driven wheels28of the BEV10. The rotating electrical machine22includes a stator32having stator windings received within slots in the stator32. The rotating electrical machine22can also include a rotor34having an inner diameter36(shown inFIG.4) configured to engage with the differential24and translate rotational movement of the rotor34to the differential24. The rotor34is received within the stator32such that as the stator windings receive electrical current, the rotor34is angularly displaced relative to the stator32.

The differential24includes a pinion gear cage38, pinion gears40, and gear pins42that hold the pinion gears40in the cage38, two output shafts44, and a housing46as shown inFIGS.3-9. The pinion gear cage38can have a substantially cylindrical shape and a ring gear48circumferentially positioned around an outer surface50of the cage38. The ring gear48can include radially-outwardly-facing gear teeth. The pinion gear cage38can include a plurality of spokes52and a central hub54that collectively define pinion gear slots56circumferentially positioned within the cage38between the spokes52and shaped to receive pinion gears40. Apertures58in the outer axial surface60of the pinion gear cage38can be shaped to closely conform to the outer surface of gear pins42and receptacles62in the hub54can be shaped to receive an end of the gear pins42. The pinion gears40can be positioned in the gear slots56such that the gear pins42may be pushed through the apertures58and the central axis of the pinion gears40such that the apertures58and receptacles62hold the pins42, as well as the pinion gears40, in place. In this implementation, the pinion gear cage38includes five pinion gears40but differentials with different quantities of pinion gears are possible. The pinion gears40can have a bore64and radially-outwardly facing gear teeth around the circumference of the pinion gears40. The gear teeth can be straight cut gear teeth in one implementation. The number of gear teeth on the pinion gears40can be chosen based on different factors, such as the number of teeth on face gears66included with the output shafts44.

Output shafts44can include the face gear66having gear teeth shaped to mesh with the gear teeth of the pinion gears40. The face gear66can be positioned at a distal end of the output shaft44and have a disk-shaped surface68that is substantially perpendicular to an axis of output shaft rotation (x) and substantially parallel to a gear face of the pinion gears40. In one implementation, the output shaft44can be cast from metal and include an annular shoulder70in which straight gear teeth are formed at the time of casting. In other implementations, the annular shoulder70and disk-shaped surface68can be relatively smooth, with straight gear teeth cut into the surface68after casting.

The housing46can be substantially tubular with a cavity for receiving the differential24and output shafts44. The outer surface of the housing46can couple with the rotor34to prevent the angular displacement of the housing46relative to the rotor34. In this implementation, the housing46can be concentrically received by the rotor34and mechanically attached such that when the rotor34rotates relative to the stator32, the housing46rotates as well. The housing46can be made from any one of a variety of materials, such as a metal alloy. At an axial midpoint along the housing46, a radially-inwardly facing surface can include gear teeth shaped to engage the ring gear48on the pinion gear cage38thereby preventing the angular displacement of the cage38relative to the housing46when the cage38is received within the housing46. The face gears66of the output shafts44can be received within the housing46such that the face gears66engage with the pinion gears40while an end of the output shafts44can extend beyond the housing46to couple with an input72of the reduction gearbox26(shown inFIG.2). Bearings74can be positioned within the housing46around an outer surface of the output shafts44and engaging the radially-inwardly-facing surface of the housing46to provide support. C-clips76can be received within grooves included in the housing46to axially constrain the elements received within the housing46.

Returning toFIG.2, the reduction gearbox26couples the output shafts44from the differential24to the driven wheels28of the BEV10. The amount of gear reduction can be selected based on the torque loads permitted by the face gears66engaging the pinion gears40. In one implementation, the reduction gearbox26includes a greater than eight-to-one gear reduction ratio, which means for every eight revolutions of the output shaft44, the driven wheel28is rotated once, and also means that the driven wheel28receives eight times the torque amount exerted at the output shaft44. It is possible that other implementations use a larger gear ratio. Also, it should be appreciated that reduction gearboxes26can be implemented in any one of a number of ways. In this implementation, the reduction gearboxes26can be a two-stage reduction gearbox having three shafts. An input shaft78includes a drive gear80that is smaller than a driven gear82coupled to an intermediary shaft84. The intermediary shaft84can include a drive gear80that engages with a driven gear82on a gearbox output shaft86that is ultimately coupled to a driven wheel28of the BEV10. The drive gears80can have a smaller diameter and fewer teeth than the driven gears82.

As the rotor34rotates relative to the stator32in response to the flow of electrical current through the stator windings, the housing46can rotate thereby communicating torque to the differential24through the housing46. The housing46transmits torque to the pinion gear cage38, through the pinion gears40to the face gears66of the output shafts44. The output shafts44can turn the drive wheels28through the reduction gearboxes26. As the BEV10operates, one drive wheel28may turn at a different speed than another drive wheel28. The differential24can compensate for this difference in angular velocity between output shafts44by virtue of the rotation of the pinion gears40permitting angular displacement of one output shaft relative to another.

It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.