Patent Application
20050023056
This invention generally relates to a drive unit assembly with an electric motor and gear drive arrangement for driving a vehicle wheel.
Conventional automotive vehicles have been powered by an internal combustion engine that provides driving torque to one or more sets of wheels to propel the vehicle as desired. Recent trends have included incorporating other sources of motive power in place of, or as a supplement to, the internal combustion engine. One such example is an electric hybrid vehicle that utilizes internal combustion engine power and electric power. One shortcoming of such alternative power arrangements is that the potential benefits are limited by the ability to incorporate such systems onto a vehicle. Designs accommodating alternative power sources are typically heavily dependent on current vehicle component configurations. Packaging space is limited and the various component design requirements present serious challenges to effective integration of alternative drive arrangements.
There is a need for alternative arrangements of supplemental or alternative power devices on vehicles so that appropriate control can be accomplished within vehicle packaging constraints. This invention addresses that need and provides a unique arrangement for providing driving torque to one or more wheels of a vehicle
A drive unit assembly for a vehicle wheel includes a rigidly mounted electric motor for driving a vehicle wheel via a gear drive. The gear drive includes at least a first gear component in driving engagement with a second gear component. The second gear component is operably coupled to drive the vehicle wheel. The gear drive includes a cycloid or epicycloid gear arrangement that provides significant speed reduction at the vehicle wheel. One electric motor can be used to drive multiple vehicle wheels or multiple electric motors can be used, with one electric motor mounted to drive each wheel independently from the other wheels.
In one disclosed embodiment, the electric motor includes a motor casing and motor output shaft that drives the gear drive. The gear drive defines a gear drive axis that is non-concentric with the motor output shaft. The motor casing is mounted to a non-rotating vehicle component, such as a suspension component, for example. The motor output shaft is preferably coaxial with the vehicle wheel.
In one disclosed embodiment, the gear drive comprises a cycloid gear configuration. In the cycloid gear configuration, the first gear component comprises a first cycloid member having a central bore for receiving and rotatably supporting an eccentric cam that is mounted for rotation with the motor output shaft and a plurality of circumferential bores spaced radially about a circumference of the first cycloid member relative to the central bore. The second gear component comprises a second cycloid member fixed to the wheel. The second cycloid member includes a plurality of drive members spaced about a circumference of the second cycloid member with each one of the drive members being received in a corresponding one of the circumferential bores. The motor output shaft is non-concentric with the central bore and each of the drive members is non-concentric with their respective circumferential bore. The eccentric cam drives the second cycloid member via the first cycloid member to achieve speed reduction at the wheel.
In another disclosed embodiment, the gear drive comprises an epicycloid gear configuration. In the epicycloid gear configuration, the first gear component comprises a non-rotating ring gear and the second gear component comprises a drive gear in driving engagement with the ring gear. The drive gear is coupled to the motor output shaft to receive driving input, and is coupled to the wheel to provide driving output to the wheel. A chain and sprocket drive interconnects the motor output shaft and the drive gear.
The combination of the gear drive and electric motor can easily provide speed reduction ratios of twenty to one and can even achieve speed reduction ratios as high as one hundred and seventy-nine to one. Thus, the subject invention provides a viable electric drive unit assembly for a vehicle wheel. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description.
A drive unit assembly 10 for a vehicle wheel 12 is shown in
The electric motor 14 is used to directly drive the vehicle wheel 12 and can be used either alone or in conjunction with a conventional internal combustion powertrain. Further, the drive unit assembly 10 could also serve as a retarding mechanism for the vehicle where power generated could be collected and stored in a power storage device 26 for subsequent use by the electric motor 14.
As shown in
As shown in
As discussed above, each of the vehicle wheels includes a gear drive 18. The gear drive 18 is needed to provide speed reduction from the relatively high-speed output from the electric motor 14 to a lower wheel speed. The gear drive 18 is preferably either a cycloid gear drive 30, shown in
The cycloid gear drive 30 of
The electric motor 14 includes a motor output shaft 44 that is received within the center bore 38. An eccentric cam and bearing pack assembly 46 is mounted on one end of the motor output shaft 44 to rotatably support the first cycloid gear component 34. The eccentric cam and bearing pack assembly 46 includes an eccentric cam member 46a that defines a cam centerline C1 and includes a plurality of bearing members 46b that cooperate with the outer circumference of the eccentric cam member 46a. The eccentric cam member 46a is either integrally formed on an end of the motor output shaft 44 or separately mounted for rotation with the motor output shaft 44. The motor output shaft 44 defines a shaft centerline S1 that is parallel to and spaced apart from the cam centerline C1, i.e., the shaft centerline S1 is non-concentric with the cam centerline C1.
A plurality of reaction members 48 are held fixed relative to the first 34 and second 36 cycloid gear components. The reaction members 48 are preferably mounted to a non-rotating vehicle structure 50, such as a wheel end housing, frame, ring gear or other similar structure. The first cycloid gear component 34 includes a scalloped or wave-shaped outer circumference surface 52 that defines a cycloidal profile. As the motor output shaft 44 drives the first cycloid gear component 34, the wave-shaped outer circumference surface 52 rolls against the reaction members 48.
A cycloid curve is generated by a point on the circumference of a circle as the point rolls along a straight line. In the cycloid gear drive 30 of the subject invention, the motor output shaft 44 is non-concentric with the center bore 38. Further, the drive members 42 are non-concentric with the circumferential bores 40, as shown in
As the eccentric cam member 46a is driven by the high speed motor output shaft 44, the first cycloid gear component 34 is forced to rotate around an internal circumference of the non-rotating vehicle structure 50. As the first cycloid gear component 34 rotates in a clockwise direction relative to the non-rotating vehicle structure 50, the wheel 12 rotates about axis 16 in a counter-clockwise direction. The cycloidal profile 52 engages progressively with the reaction members 48 fixed to the non-rotating vehicle structure to produce a reverse rotation at a reduced speed. For each complete revolution of the motor output shaft 44, the first cycloid gear component 34 turns one cycloidal tooth pitch in the opposite direction. Preferably, there is one less cycloidal tooth around the first cycloid/gear component 34 than there are reaction members 48 to achieve reduction ratios that are equal to the number of cycloidal teeth, however, other combinations could be used. The reduced rotation of the first cycloid gear component 34 is transmitted to the drive members 42 that engage the circumferential bores 40.
The electric motor 44 includes a housing or casing 54 that is fixed to a suspension component 56 or other similar vehicle structure via a motor mount 58. Due to the speed reduction provided by the cycloid gear drive 30, the electric motor 14 can be rigidly mounted at the vehicle wheel 12 and does not require further speed reducing structure.
Optionally, the epicycloid gear drive 32 can be used to provide speed reduction at the vehicle wheel 12. An epicycloid is defined as a curve traced by a point on a circle that rolls on the outside of a fixed circle. The epicycloid gear drive 32 of
The ring gear 60 and motor output shaft 44 are concentric and the drive gear 62 and motor output shaft 44 are non-concentric. The motor output shaft 44 drives the chain and sprocket drive 70, which drives the drive gear 62 within the ring gear 60. The drive gear 62 is fixed to a wheel disc 72 or other similar member via a connector member 74. The vehicle wheel 12 is fixed for direct rotation with the wheel disc 72. The wheel disc 72 includes a cup portion 76 that receives and supports the motor output shaft 44 on a bearing pack 78.
The combination of the gear drive 18 and electric motor 14 easily provides significant speed reduction ratios. Thus, the subject invention provides a viable electric power wheel drive option by using the subject drive unit assembly 10 with a rigidly mounted electric motor 14. Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
