Abstract:
Motorized wheels in a wheelchair or other light vehicle are each mounted on an axle for limited rotation relative to a secondary connection to the frame of the vehicle which incorporates a sensor providing feedback which controls the motor according to torque sensed through the secondary connection. The motor and associated gearing and control circuitry are housed within a wheel hub of which a drum supporting a wheel rim is supported at its inner surface on multiple bearings spaced around its periphery.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to motorized wheels for wheelchairs and other light vehicles, of the type in which an electric motor is built into the wheel hub, and to systems for the control of such wheels.  
         BACKGROUND OF THE INVENTION  
         [0002]    U.S. Pat. No. 5,246,082 (Alber) discloses a motorized wheel for wheelchairs and the like, in which the wheel is designed to plug into a special socket on the wheelchair, and a hub against which the motor reacts is fixed relative to the frame by an arm, radially displaced from the axis of the hub, which fixes the hub to the frame of the chair.  
           [0003]    U.S. Pat. No. 5,199,520 (Chen) discloses a wheelchair with motorized wheels, in which the wheel hubs are permanently secured to the frame of the chair, and the wheels are removable from the hubs.  
           [0004]    Both of these arrangements permit the wheels of a wheelchair or other vehicle to be removed when the vehicle is folded or otherwise prepared for transportation, but, in each case, the vehicle must be specially adapted for this purpose, and the wheels are not directly applicable to a wheelchair or other vehicle of which the hub&#39;s driving wheels are secured in tubular journals incorporated in the frame of the vehicles. Moreover, more effective and efficient control of the motors in the prior art arrangements in order to minimize electricity consumption and provide optimum assistance to a user or driver of the vehicle would be desirable. It is also important that a motorized wheel designed for application to vehicles originally designed for human propulsion does not overstress the frame of the vehicle.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to provide a motorized wheel and controls therefor which can be applied to a vehicle, which can be readily removed from the vehicle, which is less likely to apply excessive stresses to the frame of the vehicle, and which permits improved control of the motor of the wheel.  
           [0006]    According to the present invention in a first aspect, a motorized wheel for a vehicle has a hub portion, a drum supporting a rim and tire for rotation relative to the hub, the drum and hub having a common axis, the hub itself being rotatable about the common axis, a shaft by which the hub portion is mounted for pivotal motion on its axis relative to a frame of the vehicle, and a bracket mounted on the hub portion or shaft spaced from the axis, the bracket being disposed to engage a frame member of the vehicle to limit pivotal motion of the hub relative to the frame of the vehicle, the engagement being through a torque sensing device which generates signals indicative of the direction and magnitude of reaction forces between the bracket and the frame, a motor mounted within the hub portion and in driving connection with the drum portion, and a control device for the motor receiving the signals and applying feedback control to the motor according to the torque reaction developed between the wheel and the frame.  
           [0007]    According to the present invention in a second aspect, a motorized wheel for a vehicle has a drum portion supporting a wheel rim, and a hub portion housing a drive motor within the drum in driving connection with the drum portion, the drum portion being mounted for rotational movement relative to an axis of the hub portion, which is mounted by a shaft to the vehicle, mounting of the drum portion on the hub portion being by means of plural roller bearings supported by the hub portion spaced around a periphery of the drum portion.  
           [0008]    The invention also extends to a vehicle including at least one motorized driving wheel having a drum portion supporting a wheel rim, and a hub portion supporting a motor in driving connection with the drum portion, the drum portion being rotatable about the hub portion, a sensor sensing magnitude and direction of reaction forces applied to the hub by the rim portion and the motor, a battery for powering the vehicle, and a control unit receiving input from said sensor and a driver-operated control, the signals from the sensor being used to control the torque developed by the motor. 
       
    
    
     SHORT DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is an elevation of a motorized wheel for a wheelchair, with clutch components removed so that internal gearing can be seen, and with rim and tire components omitted;  
         [0010]    [0010]FIG. 2 is a corresponding elevation with the clutch components in place (upper half) and partially cut away (lower half);  
         [0011]    [0011]FIG. 3 is a cross-section on the lines  3 - 3  in FIG. 1, except for the clutch in which the section is on the lines  3 A- 3 ;  
         [0012]    [0012]FIG. 4 is a cross-section on the lines  4 - 4  in FIG. 1;  
         [0013]    [0013]FIG. 5 is a partial cross-section on the line  5  in FIG. 1;  
         [0014]    [0014]FIG. 6 diagrammatically illustrates an alternative clutch arrangement;  
         [0015]    [0015]FIGS. 7A and 7B are fragmentary cross-sections illustrating alternate means of mounting a rim and tire on the wheel.  
         [0016]    [0016]FIG. 8 is a block diagram of the electrical and electronic systems of a wheelchair incorporating the invention;  
         [0017]    [0017]FIG. 9 is a block diagram of a control system for a single wheel, showing one version of a sensor fork for engaging a frame member of the wheelchair; and  
         [0018]    [0018]FIG. 10 shows an alternative embodiment of sensor fork; 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    While the implementation of the invention is described with reference to a wheelchair, it should be understood that it is equally applicable to other vehicles such as trolleys, scooters, golf carts, etc., for which electrically powered wheel units are a suitable power source.  
         [0020]    Referring to FIGS.  1 - 5 , a wheel unit  1  comprises a stub axle  2  supporting a back plate  4  forming a hub. The stub axle is inserted into a tubular socket (not shown) in a frame of the wheelchair, in which it is retained by a nut and washer (not shown) on a threaded end  6  of the axle in a manner which allows at least limited rotational movement between the axle and the socket. A quick-release type lock to retain the axle may be used in place of a nut. Secured to the back plate through a spacer ring  8  by bolts  10  so as to form a chamber for an electric motor  17  is a further plate  12 , which also supports a ring of peripheral roller bearing assemblies  14  which support for rotation a drum  16  forming the outer peripheral wall of a hollow chamber, closed on its outer face by a plate  18  connected through dogs  20  loaded by springs  22  to a drive gear  24  concentric with the axle  2 . The dogs are moved radially in and out of engagement with the gear by a cam plate  26  operable by a manually-rotatable disc  27  mounted externally of the plate  18  so as to provide a clutch. The drive gear is journalled in the cam plates  26  by a bearing  28 , and is secured by a bolt  30  to a shaft  32  journalled in bearings  34 ,  36  located respectively in the plate  12  and a further bracket  38  secured to the plate  12 . A pinion  40  secured to a shaft  42  mounted in further bearings  44  in the plate  12  and bracket  38  drives the gear  24  and, in turn, is driven by a further gear  46  mounted on the shaft  42 . A pinion  48  is mounted on yet a further shaft  50  journalled in bearings  52  in the plate  12  and bracket  38  is driven by a gear  54  also mounted on the shaft, which, in turn, is driven by a pinion  56  mounted on the shaft of the motor  11 , the gears and pinions providing several stages of step-down gearing from the motor  11  to the drum  16 .  
         [0021]    In an alternative arrangement (not shown), the drum  16 , instead of being supported by the bearings  14 , has an inwardly extending annular plate on the side of the wheel carrying shaft  2 , supported by an annular bearing on a central portion of the plate  4 .  
         [0022]    Mounted outside of the back plate  4  is a fork  58  incorporating a load cell  59 , to be described further below. Mounted on the plate  18  within the drum  16  are a control unit  60  and an electromagnetic brake unit  62  acting through a pinion  64  on the gear  54 . Electrical cabling  66  extends from a socket  68  mounted on the plate  4  to the motor  17 , the control unit  60 , the load cell  59 , and the brake unit  62 .  
         [0023]    In an alternate clutch arrangement shown in FIG. 6, the shaft  42  supporting gear  46  and pinion  40  is journalled in a lever arm  70  pivoted at  72  to the plate  12 , an opposite end of the lever arm  70  being loaded by a spring  71  to bias the lever arm to a position in which the gear  46  is disengaged from the pinion  48  and the pinion  40  from the gear  24 . A solenoid  74  moves the gear  46  and pinion  40  into engagement. Solenoid operated and manually operated latching devices  76  and  78  are provided to latch the solenoid in a position in which the gear and pinion are engaged and may be operated to release the solenoid and thus allow the gear and pinion to disengage.  
         [0024]    Referring now to FIGS. 7A and 7B, these show two examples of ways in which a rim  80  carrying a pneumatic tire  82  may be mounted on the hub  16 . In FIG. 7A, the rim  80  carrying the tire  82  is clamped between a flange  88  on the plate  16  and a flange  90  on the plate  18 . In FIG. 7B, the rim  80  is secured by spokes  92  having end portions extending through the flanges  88  and  90  and the rim  84 .  
         [0025]    [0025]FIG. 9 is a block diagram of the electrical circuits of a wheelchair incorporating wheels L and R, constructed as already described. The wheelchair further incorporates a battery  94 , handlebars  96  and an occupant-accessible joystick control  98 . Power supply circuits are provided from the battery module to the electronic circuit blocks (not shown). The circuits comprise five main subassemblies, each of which includes a control circuit conveniently implemented by appropriately programmed digital signal processors (DSP)  100 ,  102 ,  104 ,  106  and  108 . The motors of two wheel units L &amp; R receive power from driver circuits  110  and  112  under control of the DSPs  100  and  102  which receive speed data from tachometers  120  and  122  associated with the wheels, and torque data from the torque sensors  59 , as well as receiving and transmitting data on a network connection  130 . The DSP  104  controls a battery module  114  which supplies power to the entire system including the drivers,  110  and  112 , from the battery  94 . The DSP  106  receives control signals from sensors  116  associated with handlebars  96  of the wheelchair. The DSP  108  receives control signals from sensors  118  associated with a joystick  98  operable by a user of the wheelchair. All of the DSPs communicate through the network  130 .  
         [0026]    Referring to FIG. 9 which shows in more detail the circuits associated with a single wheel L, the motor driver  110  also provides power to actuate the brake unit  62 , a feedback circuit  132  ensuring that the brake and the motor are not actuated simultaneously. A circuit  134  provides motor torque data to the DSP  100 , in addition to data as to the restraining torque sensed by the sensor (strain gauge)  59  associated with the fork  58  which act in a frame member  136  of the wheelchair through shock-absorbing springs  138 . In an alternative arrangement shown in FIG. 10, the fork  58 , instead of being mounted on the backplate  4 , is mounted on a resilient radial arm  142  incorporating the strain gauge  59  and extending from a hub  140  keyed to the stub axle  2 .  
         [0027]    In use, the wheel DSPs  100  and  102  are programmed to respond to movements of the handlebars  96  or joystick  98 , as communicated over the network  130 , in an appropriate manner, with forward pressure on the handlebars or joystick being translated proportionately into acceleration of the wheels  1  such as to accelerate the wheelchair forward, backward pressure producing rearward acceleration, and sideways movement of the joystick or differential pressure on the handlebars resulting in differential control of the motors so as to steer the wheelchair to left or right. The brake unit  62  is applied to decelerate or stop the chair when speed is too low for regeneration in the motor to produce adequate deceleration, the drive  110  accommodating regenerative braking to return energy to the battery as permitted by the control unit  114 . Incorporation of the control units  60  into the wheels saves losses in the cables connecting the battery to the wheels.  
         [0028]    The sensors  59  sense the direction and magnitude of the reaction forces between the wheel and the frame of the wheelchair and thus, as well as sensing the torque reaction between the wheels and the wheelchair frame and thus allowing the motors of the wheels to be controlled to alter the motor torque to maintain the torque reaction at a level appropriate to the signals received from the handlebars or the joystick. Additionally, the motors (and optionally the brakes) can be controlled to limit the stresses applied to the frame members  136 .  
         [0029]    Each embodiment of clutch enables the rim portion of its wheel to be released from driving connection with the hub portion, so that the wheelchair can be operated manually in the event that motor drive is not required, or not available due to a discharged battery or other failure.  
         [0030]    The above embodiment of the invention is exemplary only, and variations, both as to the type of vehicle to which the invention is applied, and as to implementation of the invention, are possible within the scope of the appended claims.