Patent Application
20190248244
The present disclosure relates to a vehicle propulsion system.
This introduction generally presents the context of the disclosure. Work of the presently named inventors, to the extent it is described in this introduction, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against this disclosure.
Automobile manufacturers are under constant and increasing pressure to improve the efficiency, performance, and fuel economy of their vehicle propulsion systems. This has led to the development of vehicle propulsion systems having alternatives to the internal combustion engine serving as a prime mover in those systems such as, for example, electric motors, fuel cells, and the like. Electric motors in these vehicle propulsion systems typically operate at high speeds with relatively high torque output. This requires a transmission which reduces the speed of the hollow rotor shaft from the electric motor to a speed which is more appropriate for a vehicle final drive. Further, the increased efficient operating speed range of an electric motor, in comparison to an internal combustion engine, reduces and/or eliminates the need to provide a transmission which has the capability to change gear ratios. As a result of these reduced requirements, automotive manufacturers have been able to simplify their propulsion systems and to more compactly position and/or combine the prime mover, transmission, final drive, and axle into a single unit, such as, for example, a transaxle.
An exemplary vehicle propulsion system 100 having a transaxle configuration is illustrated in
In an exemplary aspect, a vehicle propulsion system includes an electric motor having a hollow rotor shaft, an input drive sprocket connected to the hollow rotor shaft, a first chain mounted on the input drive sprocket, a transfer driven sprocket mounted on a transfer shaft, the first chain is also mounted on the transfer driven sprocket, a transfer drive sprocket mounted on the transfer shaft, a second chain mounted on the transfer drive sprocket, a final drive driven sprocket connected to a differential, the second chain is also mounted on the final drive driven sprocket, a first axle connected to an output of the differential, and a second axle connected to another output of the differential
In this manner, the efficiency, fuel economy, emissions, the size, simplicity, noise, vibration, and mass of a vehicle propulsion system may all be improved.
In another exemplary aspect, a ratio between the input drive sprocket and the transfer driven sprocket is greater than two to one.
In another exemplary aspect, the ratio between the transfer drive sprocket and the final drive driven sprocket is greater than two to one.
In another exemplary aspect, the system further includes a transaxle housing.
In another exemplary aspect, the system further includes a bearing mounted to the transaxle housing and rotatably supporting the transfer driven sprocket.
In another exemplary aspect, the bearing is co-planar with the transfer driven sprocket.
In another exemplary aspect, the bearing is a roller-type bearing.
In another exemplary aspect, the system further includes a bearing mounted to the transaxle housing and rotatably supporting the final drive driven sprocket.
In another exemplary aspect, the bearing is co-planar with the final drive driven sprocket.
In another exemplary aspect, the differential is a bevel gear differential.
In another exemplary aspect, the differential is a planetary spur gear differential.
In another exemplary aspect, the width of the second chain is larger than a width of the first chain.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The above features and advantages, and other features and advantages, of the present invention are readily apparent from the detailed description, including the claims, and exemplary embodiments when taken in connection with the accompanying drawings.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
Referring back to
Additionally, the inventors realize that the use of gears in these gear sets results in thrust loads which act in an axial direction. As a result, the use of gears requires bearing sets which provide support not only radially but also axially. These axial loads from the gear sets are known as thrust loads. These thrusts loads increase the demand on the bearing systems to handle not only the radial loads, but also the thrusts loads which reduces the overall efficiency of the system. For example, referring back to the system 100 in
The inventive exemplary embodiment of the vehicle propulsion system 200 of
Further, the ability to rely upon a chain/sprocket drive system rather than a gear set provides an improvement in efficiency which is increasingly important to improve fuel economy, reduce emissions and the like.
In stark contrast to the gear sets of the system 100, the chain/sprocket sets of the system 200 do not generate axial thrust loads. Therefore, the bearing sets of the system 200 do not need to handle axial thrust loads. As a result of this reduced requirement, the system 200 may incorporate roller type bearings rather than ball bearings. The ability to incorporate roller type bearings enables a more compact design and packaging. In general, roller type bearings are smaller than a comparable ball type bearing. Further, in accordance with the present disclosure use of roller type bearings, and the eliminated requirement to handle thrust loads, the bearings may be positioned to be co-planar to the chain/sprocket sets. In this manner, overall transaxle size may be much more compact than traditional transaxle designs.
Moreover, with the substantial reduction and/or elimination of thrust loads from the chain/sprocket sets, in comparison to gear sets, the size of those bearings which may continue be required to handle axial loads, such as a positioning load may also be reduced in size as positioning loads are generally much lower than thrust loads from a gear set.
Additionally, the ability to position the bearings co-planar with the chain/sprocket sets reduces and/or eliminates the requirement for the shaft carrying and/or transferring the load from any chain/sprocket set to a bearing. In this manner, the load requirement for the shaft is reduced which may further enable a reduction in the mass of the shaft. For example, referring to
In the exemplary embodiment of
It should be further noted, that the higher torque capacity of the exemplary embodiments of the present disclosure is further enabled by the combination of the chain/sprocket set and the use of a compact roller bearing that are arranged co-planar with each other. Further, the roller bearings of the exemplary embodiments may be supported directly by a housing of the transaxle, rather than by a shaft as has previously been done with conventional gear set transaxles designs. The shafts of those conventional gear set designs have had to be beefed up to support the forces and transfer those forces to the housing which requires an increase in the mass and size of those supporting shafts(s). In contrast, the co-planar bearings enable the housing to directly carry the radial load.
Referring now to
This description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims.
