Patent Publication Number: US-2019193784-A1

Title: Non-scrubbing vertical drive unit for a trackless or free roaming vehicle with zero turn radius

Description:
BACKGROUND 
     1. Field of the Description 
     The present invention relates, in general, to driven wheel assembly designs for vehicles, and, more particularly, to a vertical drive unit or, interchangeably, a driven wheel assembly that is adapted to avoid or limit scrubbing and also to provide a zero turn radius to a vehicle (which may include two or more of such driven wheel assemblies) such as trackless or free roaming vehicles in an amusement or theme park or other settings, automated guided vehicles (AGVs), and the like. 
     2. Relevant Background 
     There are many applications where it is desirable for a vehicle to be able to make very sharp turns or maneuver tight corners such as with a zero or near-zero turn radius, e.g., a 90-degree turn or moving the vehicle in an orthogonal direction to the present travel direction. In some applications including many industrial settings, it may be allowable for the wheels to scrub during such sharp turns. However, there are growing numbers of applications where scrubbing is undesirable or even unacceptable due to the noises made by the tires or wheels upon scrubbing, due to the wear on the tires that scrub, and due to marks left on the floor at each turning location. 
     As one useful example, free roaming or trackless ride vehicles are increasingly desirable in theme parks. One particularly sought after feature is for a ride vehicle to be able to change direction without a turn radius (i.e., a zero turn radius) without scrubbing of the wheels. Presently, vertical drive units that are infinitely steerable are employed in ride vehicles to rotate the wheels and to attempt to achieve a zero turn radius. However, conventional vertical drive units cannot “turn on a dime” or provide a true zero turn radius unless the wheels are allowed to scrub. In practice or use, a vehicle with such vertical drive units is traveling in a first direction (e.g., the X direction) with the vehicle facing the same first direction may come to a stop. Then, in order to move in a second direction orthogonal to the first direction (e.g., the Y direction) from that stop (without changing the orientation of the ride vehicle), all of the wheels on the vehicle have to roll forward some distance while concurrently turning the 90 degrees to change direction in order to avoid scrubbing the wheels. 
     As will be apparent to those skilled in the arts, this limits the ride profile and experience that can be achieved with ride vehicles using conventional vertical drive units. Ride designers and operators as well as other designers of trackless or free roaming vehicles desire a vehicle that can be traveling in a first direction and come to a stop and then immediately begin traveling in a second direction that is orthogonal to the first direction (i.e., make up to a 90-degree turn), thereby creating a travel (or ride) path that includes a right angle and not a rounded corner as is provided by conventional vertical drive units. 
     In any vehicle that travels the same or a similar path through a space such as a ride vehicle, scrubbing of the wheels results in reduced wheel life, excess noise, and marking of the driving surface. All of these problems with scrubbing are undesirable and have forced operators of the vehicles to avoid or limit ride or travel paths that call for zero radius turns. Vertical drive wheel units or infinitely steerable powered wheels systems provide great maneuverability, but each presently suffers from the limitation of not being able to pivot on a vertical axis without wheel scrub on the floor or contract/driving surface. 
     SUMMARY 
     Briefly, a vertical drive unit or driven wheel assembly is provided for use on any vehicle for which it is desirable to make zero radius (or right angle) turns. For example, a trackless or free roaming vehicle for theme park ride may include four of the new driven wheel assemblies to follow a ride path with one or more right angle turns. Each driven wheel assembly is configured to allow for pivoting or rotating the drive wheels on a vertical axis without wheel scrub to achieve a zero turn radius. 
     More particularly, a driven wheel apparatus or assembly is provided for use in a vehicle to provide a zero turn radius without wheel scrubbing. The assembly includes a vertical drive motor and a drive shaft driven to rotate about a vertical drive axis by the vertical drive motor. The assembly also includes a differential coupled to an output end of the drive shaft and a first wheel and a second wheel each coupled to the differential (e.g., to the outputs or side gears of the differential). The differential is positioned between the first and second wheels (such as with wheel spacing in the range of 1 to 6 inches or 0.5 to 2 inches greater than an outer diameter (OD) of the drive shaft that extends between the first and second wheels). The first and second wheels rotate about a wheel rotation axis that is orthogonal to the vertical drive axis. 
     In some embodiments, the differential is configured such that the first and second wheels are independently rotatable at matching or differing rotation velocities. In the same or other embodiments, due to the differential design/configuration, the first and second wheels can rotate in a matching rotation direction about the wheel rotation axis or in opposite rotation directions about the wheel rotation axis. To avoid or minimize scrub, the differential is configured to allow the first and second wheels to rotate in different directions about the wheel rotation axis when the draft shaft is stopped from rotating about the vertical drive axis (or the shaft is not rotating or being driven during steering to perform a sharp turn such as a 90-degree turn). To this end, the differential may be implemented as an open differential, and the first and second wheels are mechanically coupled to first and second outputs (such as side gears or the like via smaller drive shafts/axles) of the open differential. In other cases, the differential is a limited slip differential. The first and second wheels are spaced apart a distance such as a distance in the range of 1 to 6 inches. 
     In some embodiments, the driven wheel assembly further includes: (a) a mounting plate for attaching the driven wheel assembly to a body of the vehicle; (b) a collar pivotally coupling the vertical drive motor to the mounting plate; (c) a rotation gear mated to the collar, whereby the collar, the vertical drive motor, and the differential rotate with the rotation gear; and (d) a steering motor driving an output gear to rotate the rotation gear to steer the driven wheel assembly. In some cases, the steering motor is rigidly coupled to the mounting plate (e.g., to not move relative to the mounting plate during assembly operations) and has a vertical rotation axis parallel to (and offset some distance from) the vertical drive axis of the vertical drive motor. The assembly may then also include a wheel support extending from a lower surface of the rotation gear and pivotally supporting the first and second wheels (such as on one or more bearing components), whereby the wheel support and the first and second wheels rotate about the vertical drive axis with the rotation gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic or functional block drawing of a vehicle or vehicle system that includes four driven wheel assemblies or vertical drive units of the present description, with one assembly shown in greater detail; 
         FIG. 2  is a side perspective view of an exemplary driven wheel assembly for use in implementing a non-scrubbing and zero turn radius vehicle such as that shown in  FIG. 1 ; 
         FIG. 3  is an side or end view of the driven wheel assembly of  FIG. 2 ; 
         FIG. 4  is a side perspective view of the driven wheel assembly of  FIGS. 2 and 3  with the second wheel and hub removed to show additional details of the assembly; 
         FIG. 5  is a sectional view of the driven wheel assembly of  FIG. 3 ; and 
         FIG. 6  is a perspective view of one exemplary differential for use in a driven wheel assembly of the present description. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is directed toward trackless or free roaming vehicles configured to include two or more (e.g., four or more) vertical drive units or driven wheel assemblies that are each configured to provide the vehicle with a zero turn radius to allow the vehicle to make right angle or 90-degree turns without wheel scrubbing. Stated differently, each driven wheel assembly is non-scrubbing even when operated to provide a zero turn radius. One useful but non-limiting use for such drive wheel assemblies is ride vehicles for theme or amusement park rides in which each ride vehicle is trackless and is allowed free roaming as it follows a ride path with one or more right angles, and the non-scrubbing aspect reduces tire/wheel wear, leaves no or fewer wheel/tire marks on the ride&#39;s vehicle-contact surfaces, and limits (or even eliminates) undesirable vehicle noises during the ride. 
     Briefly, an exemplary driven wheel assembly includes a vertical axis motor driving or rotating a vertical drive shaft to drive first and second (or a pair of) spaced-apart wheels oriented horizontally or perpendicular to the vertical drive shaft for lateral motion of the vehicle. This is combined with an off-axis vertical motor and gear, which rotates or steers, the driven wheel assembly. Instead of a right angle gear drive as found in a conventional vertical drive unit, the driven wheel assembly employs a center differential that is coupled to the output end of the vertical drive shaft and a hub of each of the first and second wheels and that is positioned in the space between the two wheels. 
     The center differential drives the first and second wheels with one wheel being on either side of the differential. In this manner, no contact surface of the wheels are in-line with the vertical rotation axis or pivot axis of the driven wheel assembly (coinciding with the longitudinal axis of the vertical drive shaft). By utilizing a differential in the driven wheel unit, each of the first and second wheels can turn at a different rotational velocity or even in opposite directions, which eliminates wheel scrub even when the driven wheel unit rotates 90 degrees with the vehicle stopped. The driven wheel assembly uses a combination of proven mechanical systems and technologies to achieve a zero turn radius while being non-scrubbing, and this results in a more robust system that is cheaper to fabricate and maintain, is faster to operate, has a higher capacity for its size, and likely will have a longer life (or at least longer tire/wheel life due to reduced wear). 
       FIG. 1  illustrates a vehicle or vehicle system  100  that is designed to be able to move through 90-degree or right angle turns without its wheels or tires scrubbing. The vehicle  100  may be manually steered in some cases but the vehicle  100  is particularly well suited for implementation as an autonomous trackless or free roaming vehicle as may be used in a ride of a theme park, as may be used for an AGV for travel on roads and in cities, as may be used in industrial and factory settings, and the like. 
     As shown, the vehicle  100  includes body  110  with a seat(s)  112  for receiving one or more passengers (not shown). The vehicle  100  also includes a controller  114 , which is shown to be onboard and in wired communication with other vehicle components, but the controller  114  may communicate in a wireless manner with such components or may even be located off board in some implementations of the vehicle  100 . The controller  114  may include one or more processors and run a control program, as is well-known in the autonomous vehicle industry, to generate a set of drive or control signals  115  to drive and steer the vehicle  100  in a space such as along a travel or ride path with turns of any angle including right angle turns while moving or from a stopped position. The vehicle  100  further includes a power assembly  118  that may include one or more batteries for providing electrical power to electric motors on the vehicle body  110  including drive and steering motors in any including drive wheel assemblies or vertical drive units such as assemblies  120 ,  122 ,  124 ,  126 . 
     The vehicle  100  is, thus, an all-wheel drive-type vehicle with each of the drive wheel assemblies  120 ,  122 ,  124 ,  126  being able to be steerable and drivable, but other embodiments may only include another pair of the driven wheel assemblies (e.g., be front or rear-wheel drive vehicles) or may include additional driven wheel assemblies. Each assembly  120 ,  122 ,  124 , and  126  may be configured identically or at least very similarly with assembly  120  being shown in detail and with the other assemblies  122 ,  124 , and  126  being understood to include similar components and have similar functions and be operable concurrently and in a similar manner as the assembly  120 . 
     The driven wheel assembly  120  includes a mounting plate or platform  130  that is attached or mounted to the body  110 , e.g., rigidly fastened to the body&#39;s frame near or within a wheel well or the like. The mounting plate  130 , hence, does not move relative to the body  110  and provides a stationary mounting structure for other components of the driven wheel assembly  120 . The driven wheel assembly  120  further includes a vertical drive motor  132  with a vertical drive shaft  150  rotatable in either direction (as shown with arrow  152 ) about a vertical drive axis  133  of the assembly  120 . The vertical drive motor  132  is supported via collar  140  on the mounting plate/platform  130 , and the collar  140  is configured to be able to rotate or pivot about the vertical drive axis  133  relative to the mounting plate  130  during operations of the assembly  120 . Particularly, the collar  140  is rigidly coupled to a rotation gear  138  at an end/side opposite the vertical drive motor  132  and it (and the motor  132 ) rotate with the gear  138  about the vertical drive axis  133  as shown with arrow  139 . 
     To steer or rotate  139  the driven wheel assembly  120 , a steering/rotation motor  134  is provided that is affixed to and supported upon the mounting plate  130 . The steering motor  134  may be a vertical drive motor, too, with a vertical output or drive shaft  135  that extends through the plate  130  and is affixed at an outer end to an output/drive gear  136 . The output/drive gear  136  may have external teeth (not shown in  FIG. 1 ) that engage or are meshed with external teeth (not shown in  FIG. 1 ) on the periphery of the rotation gear  138  such that rotation of the shaft  135  and gear  136  as shown with arrows  137  causes the rotation gear  138  to rotate  139  as well as interconnected collar  140  and vertical drive motor  132 . Hence, operation of the steering/rotation motor  134  by the controller  114  via control/drive signals  115  is used during use of the vehicle  100  to steer the body  110  along a travel or ride path. The gear  138  typically has teeth about its entire periphery such that the steering motor  134  can be operated to provide infinite steering (e.g., more than 360 degrees in any direction) with rotation  137  of gear  136 . 
     Instead of using a single wheel, the driven wheel assembly  120  includes a first wheel  170  and a second wheel  172  that are spaced apart a distance, d, from each other and supported so as to rotate in either direction as shown with arrows  171 ,  173  about wheel rotation axis  174  that is orthogonal to the vertical drive axis  133  (e.g., wheels  170 ,  127  have a horizontal rotation axis). The distance, d, is typically kept relatively small such as less than 12 inches in many cases such as in the range of 1 to 4 inches in some useful embodiments, and this spacing between wheels  170 ,  172  is typically chosen to be only as large as needed to provide clearance for the drive shaft  150  pass between the wheels  170 ,  172 . The wheels  170 ,  172  are preferably independently rotatable  171 ,  173  at the same or differing speeds and even in the same or different directions about the axis  174 . 
     To this end, a differential (or central differential)  160  is included in the driven wheel assembly  120  and is positioned between the first and second wheels  170 ,  172 . More specifically, the differential  160  is coupled to the output/drive end of the vertical drive shaft  150  (or an input of the differential  160  engages the end of shaft  150 ). Additionally, the differential  160  (or its left and right outputs) are coupled to (or mechanically engages) the first and second wheels  170 ,  172  (e.g., a hub of each wheel  170 ,  172  is affixed to the differential  160 ) so that the wheels  170  and  172  are driven by the vertical drive motor  132  via the drive shaft  150  and the differential to rotate  171 ,  173  about the wheel rotation axis  174 . 
     The differential  160  may take a wide variety of forms to implement the assembly  120  such that the wheels  170 ,  172  may rotate  171 ,  173  independent of each other (e.g., at the same speed and direction, at differing speeds but same direction, at same speed but differing directions, or at differing speeds and direction as a locked or closed differential is not utilized). For example, some embodiments use an open differential for the center differential  160  while other embodiments use a limited slip differential for the center differential  160 . 
     The first wheel  170  and the second wheel  172  are shown to be mounted to and supported by the rotation gear  138  (e.g., rigidly affixed to a lower surface of the gear  138  in some cases) via a wheel support  142 , which may provide one or more bearing surfaces for a wheel hub or otherwise pivotally support each of the wheels  170 ,  172  to allow rotation  171 ,  173  about rotation axis  174 . In this manner, the first and second wheels  170 ,  172  are steered or rotated about the vertical drive axis  133  with rotation of the gear  138  by the steering/rotation motor  134 , and no scrubbing will occur due the inclusion and operation of the center differential  160  allowing separate/independent, different, and concurrent (when needed) rotation  171 ,  173  of the wheels  170 ,  172  (e.g., with a clutch (not shown but understood) operated (e.g., disengaged) to allow independent rotation via the differential  160  in different directions at stop and then the clutch is operated (e.g., engaged) during to move the vehicle  110  after a turn at the stop). 
       FIGS. 2 and 3  are side perspective and end or side views, respectively, of an exemplary driven wheel assembly or vertical drive unit  220  useful for implementing the assemblies  120 ,  122 ,  124 , and  126  in the vehicle  100  of  FIG. 1 . The driven wheel assembly  220  is configured to provide a zero turn radius and also to be non-scrubbing even during a 90-degree turn from a vehicle stop. As shown, the assembly  220  includes a mounting plate or platform  230  that would be fastened (or rigidly attached) to a vehicle body (or its frame such as near or in a wheel well) to support the assembly  220  in the vehicle and the plate  230  is stationary relative to the vehicle body during operations of the assembly  220 . 
     The assembly  220  further includes a vertical drive motor  232  pivotally supported upon the plate/platform  230  via collar  235  so that it can rotate about a vertical drive axis  233  (e.g., rotate relative to the stationary plate  230 ) during steering operations of the assembly  220 . The drive motor  232  is operable (in response to control signals from a vehicle controller or the like) to rotate a wheel drive shaft (or may be labeled a pinion shaft)  250  in either direction about the vertical drive axis  233  as shown with arrows  252 . The vertical drive motor  232  may be implemented using a wide variety of commercially available electric motors and may have a power capacity chosen to suit the particular vehicle upon which it will be mounted. For example, vertical drive motors (e.g., direct current (DC) motors, AC motors, AC/DC motors, induction motors, and the like) manufactured and/or distributed for electric vehicles (e.g., mobile battery-powered vehicles) and other applications by Schabmueller GmbH, C.F.R. SRL, Regal Beloit Corporation, or others may be used to implement the drive motor  232 . 
     The collar  235  is interconnected with a rotation/steering gear  238 , such that the gear  238  is pivotally couple with and supported by the plate/platform  230 , such as shown on a side opposite the vertical drive motor  232 . The rotation/steering gear  238  is rotatable about the vertical drive axis  233 , in either as shown by arrows  239 , by a steering/rotation drive  234  that operates to rotate a shaft  235  to rotate (as shown by arrows  237 ) an output gear  236  about a second vertical axis offset from vertical drive axis  233 . The steering/rotation drive  234  may take a form similar to that of motor  232  but require less power (have a lower capacity) and may be provided by the same manufacturers/distributors in some cases. The drive  234  is affixed to the plate  230  and remains stationary relative to the plate  230  during operations of the assembly  220 . The output gear  236  has external teeth about its periphery that are meshed with external teeth of the steering/rotation gear  238  such that when the motor  234  is operated to rotate the shaft  235  and interconnect gear  236 , the steering/rotation gear  238  is rotated as shown at  239 , which causes the collar  235  and interconnected vertical drive motor  232  to rotate or be steered into a new position with infinite steering (up to or exceeding 360 degrees of rotation). An additional gear  270  may be provided opposite the output gear  236  that is freewheeling to function as a guide and/or to provide feedback to a controller (e.g., be indicative of amount of rotation of gear  238 ). 
     A wheel support  242  is attached to the lower side/surface of the rotation gear  238  so that it rotates  239  with the gear  238  in response to operations of the steering/rotation drive  234 . Instead of a single wheel, the assembly  220  includes a first wheel  270  and a second wheel  272  spaced apart a distance from the first wheel  270 , and the first and second wheels  270 ,  272  are pivotally supported upon the wheel support  242  so that they are rotated about the vertical drive axis  233  with the gear  238  to provide steering of a vehicle including the assembly  220 . The pivotal mounting to the wheel support  242  is provided in some cases by supporting first and second hubs  276 ,  278  on bearings to allow each of the hubs  276 ,  278  and wheels  270 ,  272  mounted on these hubs  276 ,  278  to rotate (as shown with arrows  271 ,  273 ) about a wheel rotation axis  274 , which is orthogonal to the vertical drive axis  233  (e.g., is a horizontal rotation axis). 
     Each of the wheels  270 ,  272  can rotate  271 ,  273  independently (or together) so that the assembly  220  in non-scrubbing. To this end, the assembly  220  includes a central differential  260  positioned between the wheels  270 ,  272 . The wheel drive (or pinion) shaft  250  has its output end  251  coupled to the input (e.g., an input pinion) of the differential  260  to drive rotation  271 ,  273  of the wheels  270 ,  272  via the differential  260 . To this end, each of the hubs  276 ,  278  of the first and second wheels  270 ,  272  is coupled to one of the first and second (or left and right) outputs of the differential  260 . 
     The differential  260  may be implemented as an open differential such that differential outputs and coupled hubs  276 ,  278  and wheels  270 ,  272  can rotate concurrently at the same speeds, can rotate independently at the same or differing rotational velocities and in the same or different directions about rotation axis  274 . Other embodiments may use other differentials, such as a limited slip differential design, that allow independent rotation of the paired wheels  270 ,  272 . As can be seen in  FIG. 3 , the wheels  270 ,  272  are separated by a distance, d (e.g., a distance large greater than an outer diameter of the drive shaft  250  such as 1 to 3 inches or more), and, as a result, none of the surfaces of the wheels  270 ,  272  is in line with the vertical rotation axis  233  or pivot axis (which coincides with axis  233  in the assembly  220 ) and by utilizing the differential  260 , each wheel  270 ,  272  can turn  271 ,  273  at a different rotational velocity or even in opposite directions about axis  274 , whereby wheel scrub is eliminated with assembly  220 . 
       FIG. 4  illustrates a side perspective view of the driven wheel assembly  220  of  FIGS. 2 and 3  with the second wheel  272  and its hub  278  removed showing additional details of the assembly  220 . Further, in this regard, the wheel support  242  is again (as with  FIGS. 2 and 3 ) shown to be transparent to show features and components of the assembly  220 . Particularly,  FIG. 4  shows in greater detail that the output end  251  of the shaft  250  that is driven by the vertical drive motor  232  mechanically engages an input (e.g., an input pinion)  462  of the differential  260  so as to input the rotation  252  of the shaft  250  into the differential  260  and, thereby, to wheel  270  (and wheel  272  (not shown in  FIG. 4 )). 
     Further, as shown, the differential  260  has first and second outputs  466  and  468  (or left and right outputs), and each of these is coupled to a wheel hub  278  or  276  so that a wheel  272  or  270  rotates with that particular differential output  466  or  468 . As shown, an output shaft or axle  469  is shown to rigidly affix the hub  276  of wheel  270  to the differential output  468 . The outputs  466 ,  468  may take a variety of forms to practice the invention but may be or include side gears when the differential  260  is provided in the form of an open differential. 
       FIG. 5  is a sectional view of the driven wheel assembly  220  shown in  FIG. 3 , and this view provides additional detail of the assembly  220 . For example, the second output (or side gear)  568  is shown to be rigidly connected to the inner surface of the second hub  278  via a shaft or axle  569 , and this mechanical coupling causes the hub  278  to rotate with the differential output  568  along with wheel  272  (which is mounted onto the hub  278 ).  FIG. 5  also shows more clearly that the drive shaft  250  has its output end  251  attached to the differential input  462  to allow the shaft  250  to drive the differential  260  during operations of the vertical drive motor  232 . 
     Further, to this end, the vertical drive motor  232  is shown to include an internal shaft  534  with its output end  535  coupled via collar to the input end  551  of the drive shaft  250 . Hence, operations of the motor  232  drives interconnected shafts  534  and  250  to rotate together in either direction and at a desired rotation velocity about the vertical drive axis  233  of the assembly  220 . The differential  260  is configured to provide this rotation along a horizontal rotation axis  274  to the two spaced-apart wheels  270 ,  272 , which are allowed to rotate in the same or differing directions together or independently and at the same or differing rotation velocities due to the well-known operating principles of the differential  260  (e.g., an open differential, an LSM differential, or other differential design allowing separate rotation (or not closed/locked) of the wheels  270 ,  272 ). 
     Although the invention has been described and illustrated with a certain degree of particularity, the particular implementations described in the present disclosure has been as examples, and numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as claimed. 
     For example, a wide variety of designs may be used to implement a differential in a driven wheel assembly (e.g., for the differential  160  of the driven wheel assembly  120 . One useful differential  600  is shown in  FIG. 6 , but other designs also may be used. As shown, the differential  600  includes a carrier  670  (or gear carrier and bearing housing). The differential  600  further includes a pinion gear  610  attached to a vertical drive shaft  605 , and a ring gear  620  attached to the carrier  670 . The differential  600  also include a left side gear  630  that would be attached (when in a driven wheel assembly) to a left axle shaft and left wheel hub, and, similarly, the differential  600  includes a right side gear  640  that would be attached to a right axle shaft and right wheel hub. Additionally, the differential  600  includes a first spider gear  650  that rides in a bearing on carrier  670  and further includes a second spider gear  660  that rides in a bearing on carrier  670 .