Patent Application
20230151875
The present disclosure generally relates to motor driven systems and more specifically, to drive systems with gear architectures providing desired and optimized performance by leveraging high speed motor input with minimized driveline origin loss inducing loads.
Motor driven systems of apparatus such as vehicles and other equipment and machinery, provide a motive force/torque for a variety of purposes. In applications such as a driveline of an electrified vehicle, power for the motor is at a premium and is preferably conserved. When employing relatively high speed motors, any added loads on the motor shaft tend to significantly increase power consumption leading to reduced operational range of the vehicle. In other various applications, added loads from the driven system may lead to a need to oversize the motor and/or to employ heavier bearings. Any added weight in battery powered vehicle applications may also lead to reduced range and so is preferably avoided.
In a number of applications, a motor may be coupled to the driven load through a gearing arrangement that increases or reduces rotational speed and torque. The gearing arrangement may take a variety of forms and generally, the moving parts include gears (simple or planetary), shafts and bearings. Any moving mechanical system has inefficiencies that arise from sources such as friction and other generated forces. Bearings and lubricants are often employed to reduce friction, increasing efficiency and performance while reducing wear. As the desire to further reduce inefficiencies increases, such as in battery powered vehicle applications, additional improvements would be beneficial.
Accordingly, it is desirable to provide motor driven systems for a variety of applications that result in appropriate performance characteristics such as torque/force requirements, and that provide desired levels of efficiency at minimized cost. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
Systems are provided for delivering power through a drive system with desirable performance characteristics such as operating a motor at high efficiency. In a number of embodiments, a drive system includes a motor and a gear system coupled with the motor by a shaft. At least one input gear is disposed on the shaft. One transfer shaft includes a transfer gear meshing with the input gear(s). Another transfer shaft includes an additional transfer gear meshing with the input gear(s). The gear system is configured to cancel axial forces at the shaft to avoid loads on the motor.
In additional embodiments, two input gears are opposite handed helix gears configured to cancel the axial forces at the shaft. The gear system is also configured to cancel at least one of radial and tangential forces
In additional embodiments, an output shaft carries a pair of output gears that are helix gears with opposite handed helix angles.
In additional embodiments, an additional pair of transfer gears are disposed on the transfer shafts and mesh with the output gears. The additional transfer gears are configured to cancel radial and tangential forces of the transfer gears and the output gears.
In additional embodiments, one of the input gears and one of the output gears have common handed helix angles, and the other of the input gears and the other of the output gears have different common handed helix angles.
In additional embodiments, one of the input gears and one of the output gears have helix angles defining a ratio of tangents approximately equal to a ratio of pitch diameters of two of the transfer gears on opposite transfer shafts.
In additional embodiments, bearings disposed on the transfer shaft(s), are configured to allow axial motion of the transfer shaft(s).
In additional embodiments, four pairs of meshing gears are included in the gear system. The output shaft carries a pair of output gears. The four pairs of meshing gears include one input gear meshing with a first of the transfer gears, the other input gear meshing with a second of the transfer gears, a third of the transfer gears meshing with one of the output gears and a fourth of the transfer gears meshing with the other output gear.
In additional embodiments, two transfer shafts are coaxial. One transfer shaft is a hollow shaft with a portion of the other transfer shaft extending through the hollow shaft.
In additional embodiments, an output shaft carries a pair of output gears. At least one output gear is a helix gear with a first helix angle of a first magnitude. At least one input gear is a helix gears with a second helix angle of a second magnitude that differs from the first magnitude enabling self-correction of force generation in the drive system.
In a number of additional embodiments, a drive system includes a motor and an input shaft driven by the motor that rotates about an input axis. A gear system is coupled with the motor by the input shaft, and includes first and second input gears disposed on the input shaft. A first transfer shaft includes a first transfer gear meshing with the first input gear, and a second transfer shaft includes a second transfer gear meshing with the second input gear. The first transfer gear and the first input gear include structures configured to cancel at least one of axial, radial and tangential forces of the second transfer gear and the second input gear at the input shaft. The first transfer shaft rotates about a first transfer axis and the second transfer shaft rotates about a second transfer axis. The input axis, the first transfer axis, and the second transfer axis all lie approximately in a common plane.
In additional embodiments, the first and second input gears comprise opposite handed helix gears with helix angles of a common magnitude and are configured to cancel the axial forces at the input shaft.
In additional embodiments, an output shaft is disposed on an output shaft axis. A first output gear is disposed on the output shaft, and a second output gear is disposed on the output shaft. The output gears comprise helix gears with opposite handed helix angles, and the output shaft axis lies outside the common plane.
In additional embodiments, a third transfer gear is disposed on the first transfer shaft and meshes with the first output gear. A fourth transfer gear is disposed on the second transfer shaft and meshes with the second output gear. The first output gear and the second output gear have a common pitch diameter.
In additional embodiments, the first and second input gears comprise a first double helix arrangement on the input shaft, and the first and second output gears comprise a second double helix arrangement on the output shaft. The first input gear and the first output gear have first common handed helix angles. The second input gear and the second output gear have second common handed helix angles.
In additional embodiments, a first bearing is disposed on the first transfer shaft and a second bearing is disposed on the first transfer shaft. A third bearing supports the second transfer shaft, and a fourth bearing supports the second transfer shaft. The first and second bearings are configured to allow axial motion of the first transfer shaft, and the third and fourth bearings are configured to allow axial motion of the second transfer shaft.
In additional embodiments, four pairs of meshing gears are included in the gear system, and an output shaft carries a first output gear and a second output gear. The four pairs of meshing gears include the first input gear meshing with the first transfer gear, the second input gear meshing with the second transfer gear, a third transfer gear meshing with the first output gear and a fourth transfer gear meshing with the second output gear. A first power flow path is defined from the input shaft, through the first input gear to the first transfer gear, through the first transfer shaft, and through the third transfer gear to the first output gear and to the output shaft. A second power flow path is defined from the input shaft, through the second input gear to the second transfer gear, through the second transfer shaft, and through the fourth transfer gear to the output shaft.
In additional embodiments, an output shaft in included in the gear system. The first and second transfer shafts are disposed at equal offset angles relative to the output shaft.
In additional embodiments, first and second output gears are disposed on an output shaft. The first and second input gears have a first common pitch diameter. The first and second output gears have a second common pitch diameter. The first and second output gears comprise output helix gears with first helix angles of a first magnitude. The first and second input gears comprise input helix gears with second helix angles of a second magnitude. The first magnitude differs from the second magnitude enabling self-correction of force generation in the drive system.
In a number of other embodiments, a drive system includes a motor driving an input shaft. A gear system drives an output shaft and is coupled with the motor by the input shaft. The gear system includes first and second input gears disposed on the input shaft. A first transfer shaft includes a first transfer gear meshing with the first input gear, and a second transfer shaft includes a second transfer gear meshing with the second input gear. The first transfer gear and the first input gear are configured to cancel radial and tangential forces of the second transfer gear and the second input gear at the input shaft. The gear system includes at least one output gear on the output shaft, the at least one output gear coupled with at least one of the first and second transfer shafts through a third transfer gear. The first and second input gears comprise a first double helix gear arrangement on the input shaft.
The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, brief summary or the following detailed description.
For the systems disclosed herein, motor input is delivered to a load through a gear system with balanced axial, radial and/or tangential forces. Balancing the axial, radial and/or tangential forces reduces loads, such as those introduced by the gearing onto the motor, leading to optimal performance, reduced weight, and improved efficiency. In a number of embodiments, a pair of transfer shafts include transfer gears that mesh with input gears on an input shaft and gears that mesh with output gears on the output shaft. The transfer shafts may be physically disposed to balance radial forces on the input and/or output shafts, when desired. In embodiments, the gearing arrangement enables the transfer shafts to each have gears with opposite helix angles and therefore to impose axial thrust reactions on the input and the output shafts in opposite directions cancelling the axial forces on the motor and on the downstream driveline. Reference to cancel forces herein means avoiding, eliminating, negating and/or nullifying forces, fully, or at least partially. Axial forces may be canceled on select transfer shafts through the use of axially floating shafts via appropriate bearings to self-correct for variations. Two independent load paths from input to output may be provided through individual and/or double gear meshes. Specific helix angles and paired arrangements of the gears on the shafts optimize alignment and other aspects of operation of the gearing. Radial and/or tangential forces may be avoided or canceled, at least partially, so as to not cause loads on the motor shaft. Losses may be further reduced by locating the transfer shafts at or near opposite sides of the motor axis. Minimizing the axial, radial and/or tangential forces on the motor provides a number of benefits such as lower loads leading to reduced power consumption. In addition, lighter weight components such as bearing may be used to support the various shafts under lower loads. Friction losses may be minimized by balancing the loads and providing smoother quieter operation.
Referring to
In the current embodiment, the vehicle 20 may be any type of vehicle. The motor 24 may be operated by any means and in the current embodiment is an electric motor and accordingly, the power supply 22 may be an electrical power supply including a battery bank. As such, operation of the drive system 21 to propel the vehicle 20 may be limited by the storage capacity of power supply 22 leading to a limited electric operation range of the vehicle 20. Any reduction in power consumption is therefore beneficial in extending the range of the vehicle 20. The motor 24 may be configured to run at a variety of speeds including relatively high speeds which may compound any loads or losses introduced by any characteristics of, or inefficiencies in, the drive system 21. In a number of embodiments, the motor may spin at 10-25 times the number of revolutions per minute of the shaft 36 leaving the gear system 26, and so any effects introduced into the motor may be amplified by the speed. For example, the motor may operate up to 30,000 revolutions per minute and the output shaft may turn at a respective 1200 revolutions per minute. In other embodiments, any gearing ratio appropriate for the application may be used.
The gear system 26 may be any of a variety of configurations of gears and shafts. Mechanical excitation may occur during operation including from the mesh of the gears in the gear system 26 as a source. The excitation may lead to the transmission of forces and motions through the shafts and bearings and to the gear housing 40, which may in turn radiate noise. Accordingly, in the current embodiment the gear system 26 may employ helical gears for benefits including noise avoidance. Helical gears may run more smoothly and quietly than other types of gears such as spur gears with less noise and vibration being generated.
Example helical gears 41, 42 are illustrated in
As shown in
The gear system 26 includes a pair of transfer shafts 61, 62. The transfer shaft 61 is supported by bearings 63, 64 and rotates about an axis 65, and the transfer shaft 62 is supported by bearings 66, 67 and rotates about an axis 68. The bearings 63-64 and 66-67 are of a configuration that allows the shafts 61, 62 to move, at least slightly, along their respective axis 65, 68. This axial movement enables the shafts 61, 62 to seek positions, such as in response to the force 50 and/or as a result of variations in cutting of the teeth 45, to assist in relieving the axial forces/thrust without transferring those to the motor 24 or to the differential 28. For example, the bearings 63-64 and 66-67 may be of the cylindrical or needle roller type with a sleeve/cup 69 and rollers 70. The gears 71-78 may be rigidly fixed to their respective shafts 34, 36, 61, 62 and the bearings 63-64 and 66-67 relieve the axial forces/thrust.
To transfer rotation, movement, and power from the shaft 34 to the shaft 36, a split power path is provided through the transfer shafts 61, 62 and through gears 71-78. In the current embodiment, all of the gears 71-78 are helical gears with meshing gears of opposite handed configuration so each meshing pair includes a right handed version (R) and a left handed version (L). In other embodiments, other gear types may be used. A first power flow path is provided from the shaft 34, through the gears 71 and 75, through the transfer shaft 62, through the gears 76 and 77, and to the shaft 36 at the hub 56. A second power flow path is provided from the shaft 34, through the gears 72 and 73, through the transfer shaft 61, and through the gears 74 and 78 to the shaft 36 at the hub 56.
Gears 71 and 72 are disposed on, and rotate with, the shaft 34 as an input shaft from the motor 24. Gears 73 and 74 are disposed on, and rotate with, the transfer shaft 61. Gears 75 and 76 are disposed on, and rotate with, the transfer shaft 62. Gears 77 and 78 are coupled and rotate with the shaft 36 as an output shaft. Gears 71 and 75 mesh with each other, are opposite handed relative to one another, and have helix angles of equal magnitude. Gears 72 and 73 mesh with each other, are opposite handed relative to one another, and have helix angles of equal magnitude. Gears 76 and 77 mesh with each other, are opposite handed relative to one another, and have helix angles of equal magnitude. Gears 74 and 78 mesh with each other, are opposite handed relative to one another, and have helix angles of equal magnitude. Gears 71 and 72 have a common pitch diameter. Gears 77 and 78 have a common pitch diameter. The gear system 26 may provide a reduction ratio between the shaft 34 to the shaft 36 of approximately 10:1 to 20:1. The rotational speed of the transfer shafts 61 and 62 may be approximately one-third that of the input shaft 34.
The gearing arrangement of
Referring additionally to
To further optimize performance, including to minimize losses and loads on the motor 24, the gears 77 and 78 at the shaft 36 have opposite handed helix angles of equal magnitude and have a common pitch diameter. In addition, the gears 71 and 77 have common handed helix angles and the gears 72 and 78 have common handed helix angles. In addition, the gear 71 and the gear 77 have helix angle magnitudes with a ratio of tangents equal, or approximately equal to, a ratio of pitch diameters of the gears 75 and 76. Further, the offset angles 87 and 89 between the axis 58 and the transfer shafts 61, 62 for optimized for packaging and force reduction purposes. The helix angles of the gears 77, 78 have magnitudes that differ, by a number of degrees, from the helix angles of the gears 71, 72 providing an additional degree of freedom to self-correct for force generation in the drive system 21 and to avoid restriction. As a result, loads on the motor 24 and on the bearings 51-55 are minimized resulting in optimized performance with maximum efficiency, and enabling the use of smaller lighter weight components, for maximized vehicle range. Force generation in the drive system may occur, such as due to variations in manufacturing tolerances and/or inexact meshing or rotation. Examples include index error, wobble, eccentricity error, or other irregularities. For example, index error may arise due to the angular relationship of gear teeth between decks or planes. Wobble may occur under operating conditions of a shaft where a combination of support stiffness and shaft stiffness may cause movement from the shaft's center axis. Eccentricity may occur under operating conditions of a gear and its shaft where the center axis of the shaft in not concentric with the reference center axis of the gear.
An alternate gear location arrangement is depicted in
An alternate bearing arrangement is shown in the drive system 21 of
As illustrated in
An alternative gear arrangement for the gear system 26 is illustrated in
As illustrated in
An embodiment as illustrated in
Another double helix input and single helix output with two transfer shafts embodiment is illustrated in
Accordingly, motor driven systems are provided that address axial, radial and tangential force balancing to reduce loads, including on the motor. Pairs of transfer shafts with gears engage double gears on the input (motor) shaft and/or output (differential) shaft. The transfer shafts may be arranged on opposite sides, or on a common side, of the input and/or output shafts to reduce net radial loading of the input and/or output shafts, especially the input shaft. Opposing input helix angles and opposing output helix angles are provided to eliminate/optimize total thrust on the transfer shafts. Transfer shafts may be mounted to allow axial movement, such as with cylindrical roller bearings, for example, to allow each shaft to seek the optimum axial location to accommodate input and output gearing with little or axial movement, such as between an electric traction motor and a differential drive to wheels through half-axles. In applications, the handedness of the helix angles of the gears in an embodiment may be modified. For example, in the embodiment of
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.
