WO2013112158A1

WO2013112158A1 - Wheel assembly for vehicle

Info

Publication number: WO2013112158A1
Application number: PCT/US2012/022737
Authority: WO
Inventors: James Leo Weber
Original assignee: Magna E-Car Systems Of America Inc.
Priority date: 2012-01-26
Filing date: 2012-01-26
Publication date: 2013-08-01

Abstract

In a first aspect, the invention is directed to a wheel assembly for a vehicle, including a wheel, a brake, an electric motor, and optionally a gearbox, and a support structure that supports the motor, the wheel and the optional gearbox if a gearbox is provided. The brake includes a brake disk that rotates with the wheel, and a caliper, which is itself made up of first and second caliper portions. The first caliper portion is formed directly in the support structure.

Description

Title: WHEEL ASSEMBLY FOR VEHICLE

FIELD OF THE INVENTION

[0001] The present invention relates to electric vehicles (ie. vehicles that are powered at least partly by an electric motor) and more particularly to electric vehicles with drive motors that are positioned at one or more wheels.

BACKGROUND OF THE INVENTION

[0002] Electric vehicles offer the promise of powered transportation through the use of electric motors while producing few or no emissions. Some electric vehicles are powered by electric motors only and rely solely on the energy stored in an on-board battery pack. Other electric vehicles are hybrids, and include an internal combustion engine, which may, for example, be used to assist the electric motor in driving the wheels (a parallel hybrid), or which may, for example, be used solely to charge the on-board battery pack, thereby extending the operating range of the vehicle (a series hybrid). Yet other electric vehicles are in the form of fuel cell vehicles, which use on-board fuel cells to produce electrical energy for powering one or more electric motors, which in turn drive the vehicle's wheels. In some vehicles, there is a single, centrally-positioned electric motor that powers one or more of the vehicle wheels, and in other vehicles, one or more of the wheels have an electric motor positioned at each driven wheel.

[0003] While currently proposed and existing vehicles are advantageous in some respects over internal-combustion engine powered vehicles, there are problems that are associated with some electric vehicles. For example, the electric motors can be expensive to replace. It would thus be advantageous to be able to provide an electric motor with an extended operating life. A separate issue is that some electric vehicles can achieve high speed, but would benefit from being able to generate high torque when needed. It would also be advantageous to provide a drive assembly for an electric vehicle that could be easily tailored by the manufacturer to meet the needs of different applications. In other words, it would be advantageous if the manufacturer could easily change the gearing in the drive assembly for different applications.

SUMMARY OF THE INVENTION

[0004] In a first aspect, the invention is directed to a wheel assembly for a vehicle, including a wheel, a brake, an electric motor, and optionally a gearbox, and a support structure that supports the motor, the wheel and the optional gearbox if a gearbox is provided. The brake includes a brake disk that rotates with the wheel, and a caliper, which is itself made up of first and second caliper portions. The first caliper portion is formed directly in the support structure. [0005] In a particular embodiment of the first aspect, the invention is directed to a wheel assembly for a vehicle, including a support structure, a wheel, an electric motor and a brake. The wheel is rotatably supported by the support structure for rotation about a wheel axis. The electric motor includes a stator and a rotor. The stator is supported by the support structure. The rotor is operatively connected to the wheel. The brake includes a brake disk connected for rotation with the wheel, and a brake caliper including an outboard caliper portion and an inboard caliper portion . The inboard caliper portion includes at least one inboard fluid chamber, at least one inboard piston movable within the at least one inboard fluid chamber, and an inboard brake pad. The at least one inboard fluid chamber is contained in the support structure. Optionally and preferably, the support structure includes at least one first fluid conduit extending therethrough to the at least one inboard fluid chamber. The at least one inboard fluid chamber and the inboard brake pad are positioned such that introducing fluid at a selected pressure into the at least one inboard fluid chamber urges the inboard brake pad against an inboard side of the brake disk. The outboard caliper portion is mounted to the support structure and includes at least one outboard fluid chamber, at least one outboard piston movable within the at least one outboard fluid chamber, and an outboard brake pad, which are positioned such that introducing the fluid at the selected pressure into the at least one outboard fluid chamber urges the outboard brake pad against an outboard side of the brake disk.

[0006] In a second aspect, the invention is directed to a vehicle that includes at least one wheel that is driven by an electric motor, which is powered by a battery pack in the vehicle. A mechanical brake is provided for the wheel, such as, for example, a disk brake, or a drum brake. When driving the vehicle, if the driver depresses the brake pedal slowly, a first portion of the travel of the brake pedal does not result in actuation of the mechanical brake, but instead results in driving the motor as a generator to generate electricity to charge the battery pack. If the pedal is depressed beyond the aforementioned first portion of its travel the mechanical brake is actuated. Optionally, the mechanism used to control whether the mechanical brake is actuated provides a feel for the brake pedal that is natural. When the brake pedal is depressed quickly, however, the mechanical brake is actuated even in the aforementioned first portion of the brake pedal travel. [0007] In a particular embodiment of the second aspect, the invention is directed to a vehicle, including a chassis, a plurality of wheels supporting the chassis, wherein the plurality of wheels includes a driven wheel, an electric motor operatively connected to the driven wheel, a battery pack for use in powering the electric motor, a controller, and a mechanical brake that is actuatable to arrest rotation of the driven wheel. The mechanical brake includes a rotating member that is associated with the driven wheel and a braking member that is movable to engage the rotating member frictionally to arrest rotation of the rotating member. The brake linkage operatively connects a brake pedal to the braking member. The brake linkage includes a selective lost motion hydraulic cylinder. The hydraulic cylinder includes a housing, a piston and a hydraulic fluid in the housing. The hydraulic cylinder includes a fluid passageway between a first housing portion on a first side of the piston and a second housing portion on a second side of the piston . The piston has an available stroke associated therewith. The hydraulic fluid has a first viscosity during movement of the piston against the hydraulic fluid at a first piston speed. The hydraulic fluid has a second viscosity that is higher than the first viscosity during movement of the piston against the hydraulic fluid at a second piston speed that is higher than the first piston speed. The brake pedal is operatively connected to a first end of the hydraulic cylinder which is on one of the piston and the housing. A second end of the hydraulic cylinder is on the other one of the piston and the housing and is operatively connected to the braking member. Movement of the brake pedal from a first brake pedal position to a second brake pedal position at a first pedal speed causes movement of the first end at a first speed between a first position for the first end and a second position for the first end, wherein movement of the first end at the first speed between the first position for the first end and the second position for the first end causes relative movement between the piston and the hydraulic fluid against each other at the first piston speed such that a first volume of hydraulic fluid flows through the fluid passageway from the first housing portion to the second housing portion, and urges the second end to move with a first force that is too low to actuate the braking member. Movement of the brake pedal from the first brake pedal position to the second brake pedal position at a second pedal speed causes movement of the first end at a second speed between the first position for the first end and the second position for the first end. Movement of the first end at a second speed between the first position for the first end and the second position for the first end causes relative movement between the piston and the hydraulic fluid against each other at the second piston speed such that a second volume of hydraulic fluid that is smaller than the first volume of hydraulic fluid flows through the fluid passageway from the first housing portion to the second housing portion, and urges the second end of the hydraulic cylinder to move with a second force that is sufficient to actuate the braking member. During movement of the brake pedal from the first position to the second position at the first pedal speed, the controller operates the electric motor as a generator and generates electricity used to charge the battery pack. [0008] In a third aspect, the invention is directed to a drive assembly for a vehicle, including a support structure, an electric motor and a gearbox. The motor includes a stator and a rotor. The gearbox includes a gearbox output member, which may be a planet carrier in embodiments in which the gearbox is a planetary gearbox. The rotor is supported at one end on the support structure by a first motor bearing, and is supported at a second end on the gearbox output member by a second motor bearing.

[0009] In a fourth aspect, the invention is directed to a wheel assembly for a vehicle, including a support structure a support structure having an inboard end and an outboard end and an inner surface that defines an interior, a motor including a stator and a rotor which are supported on the inner surface and which are contained in the interior, a gearbox that is positioned outboard of the motor and is supported by the inner surface, and a wheel that is driven by the motor through the gearbox and is supported by the inner surface.

[0010] In a fifth aspect, the invention is directed to a vehicle that includes an anti-lock braking system. The vehicle includes a chassis, a plurality of wheels supporting the chassis including a first driven wheel on a first side of the vehicle and a second driven wheel on a second side of the vehicle, a first electric motor operatively connected to the first driven wheel, a second electric motor operatively connected to the second driven wheel, and a controller configured to determine the speeds of the first and second wheels and to determine if each of the first and second wheels is about to skid. Based on the determination, the controller is programmed to control the braking torque applied to each of the first and second electric motors to inhibit skidding of rhe first and second wheels. The vehicle may include a hydraulic braking system to complement the braking that is provided by the electric motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will now be described, by way of example only, with reference to the attached drawings, in which: [0012] Figure 1 a is a perspective view of a wheel assembly for a vehicle in accordance with an embodiment of the present invention;

[0013] Figure 1 b is a perspective view from another viewpoint of the wheel assembly shown in Figure 1 a;

[0014] Figure 2 is a sectional side view of the wheel assembly shown in Figure 1 a;

[0015] Figure 3 is a sectional perspective view of a portion of the wheel assembly shown in Figure 1 a, including part of a support structure and a gearbox;

[0016] Figure 4 is a partially exploded perspective view of the wheel assembly shown in Figure 1 a, without the wheel;

[0017] Figure 5 an exploded perspective sectional side view of the components shown in Figure 4;

[0018] Figure 6 is a magnified sectional side view of the corner assembly shown in Figure 1 a; [0019] Figure 7a is a sectional perspective view of a portion of a brake caliper shown in Figure 1 a;

[0020] Figure 7b is a sectional side view of the portion of a brake caliper shown in Figure 7a;

[0021] Figure 8 is a perspective view of the wheel assembly shown in Figure 1 a without the wheel;

[0022] Figure 9 is an exploded perspective view of an alternative brake caliper for use instead of the caliper shown in Figure 7a; [0023] Figure 10 is a schematic illustration of a vehicle in which a plurality of wheel assemblies shown in Figure 1 , showing both a regenerative braking system using the motors from a plurality of the wheel assemblies shown in Figure 1 a, and a hydraulic brake system using the brake from the wheel assembly shown in Figure 1 a;

[0024] Figure 1 1 is a perspective view of a shoe assembly that is part of the wheel assembly shown in Figure 1 a;

[0025] Figure 12 is a plan view of a shoe actuation linkage shown in Figure 1 1 ; [0026] Figure 13 is another partially exploded perspective view of the wheel assembly shown in Figure 1 a without the wheel;

[0027] Figures 14a and 14b are side views of a brake pedal which is used to actuate the regenerative braking system shown in Figure 10, and which is also used to actuate the hydraulic braking system, in a first position and in a second positions;

[0028] Figure 15a and 15b are graphs illustrating the relationship between brake pedal travel and braking torque under two different conditions;

[0029] Figure 16 is a graph illustrating the relationship between brake pedal travel and brake pedal force; and [0030] Figure 17 is another magnified sectional side view of the wheel assembly shown in Figure 1 with the wheel removed.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Reference is made to Figure 1 a, which shows a wheel assembly 10 for a vehicle, shown at 208 in Figure 10. The corner assembly 10 may be suitable for several types of electrically powered vehicles. For example, embodiments of the wheel assembly 10 may be suitable for vehicles that are used on-road (eg. passenger cars), vehicles that will be used off-road (eg. sport-utility vehicles), civilian vehicles, military vehicles, high speed vehicles (eg. sports cars) and high-torque vehicles.

[0032] As more clearly shown in Figure 1 b, the wheel assembly 10 includes a drive assembly 24, a wheel 20, a brake 18 (Figure 1 a), and an optional adapter 262 which can be used to receive suspension and steering elements. Referring to Figure 2, the drive assembly 24 includes a support structure 12, an electric motor 14 and a gearbox 16. In some instances, the brake 18 may be omitted, as mechanical means for braking the wheel 20 may be provided by a customer that purchases the wheel assembly 10. The wheel 20 has associated therewith a wheel axis shown at 27.

[0033] The support structure 12 includes a main support structure portion 28 and an inboard cover 30. The support structure 12 has an inner surface 32 (see Figure 3) that defines an interior 38, and an outer surface 34 (Figure 4). Referring to Figure 2, the support structure 12 further has an inboard end 40 and an outboard end 42. The support structure 12 may be made from any suitable material, such as, for example, nodular iron.

[0034] The outer surface 34 (Figure 4) of the support structure 12 includes a first, inboard portion 44, and a second, outboard portion 46 that is radially smaller than the inboard portion 44. A transition portion 48 separates the inboard and outboard portions 44 and 46.

[0035] The motor 14 may be a radial flux motor, as shown in the figures, and includes a stator 50 and a rotor 52. The stator 50 includes a stator core 54 (laminations) and a plurality of stator magnets 56 (Figure 5). The stator 50 is mounted to the support structure 12 by a plurality of stator fasteners 58 (eg. bolts) shown in Figure 6. To assist in reducing vibration in the stator 50, the stator 50 may be made relatively thick radially, and relatively high clamping forces may be applied through the stator fasteners 58 using wave washers 59 or the like, to hold the stator 50 to the support structure 12. Clamp forces may be, for example, about 765 lbs (force), and for example, 1 1 stator fasteners 58 may be used to hold the stator 50 to the support structure 12. In the embodiment shown, the stator 50 is supported on the first radially inner surface 32 of the support structure 12.

[0036] The stator fasteners 58, in at least some embodiments, are threaded and may thus not be ideally suited for positioning the stator 50 in a specific selected position (eg. centered about the wheel axis 27). To provide more precise positioning for the stator 50, a plurality of dowels shown at 60 in Figure 2, 3, and 5) may be provided, which pass through apertures in the stator 50 and into apertures in the support structure 12. These dowels 60 may be made from any suitable material, such as a suitable steel alloy.

[0037] Power may be sent to the motor 14 from within the vehicle via any suitable electrical conduits (not shown).

[0038] The motor 14 includes an optional cooling jacket 70. The cooling jacket 70 is positioned inside the support structure 12 (ie. in the interior 38) and is in direct contact with the stator 50. The stator fasteners 58 hold the cooling jacket 70 in place on the support structure 12.

[0039] The cooling jacket 70 includes a first, radially inner, jacket housing member 72, a second, radially outer, jacket housing member 74 and an internal channel structure 76 that directs a flow of cooling fluid (eg. a mixture of water and glycol), through the cooling jacket 70 from a fluid inlet 78 (Figure 1 b) to a fluid outlet 80 (Figure 1 b). The cooling jacket 70 (Figure 6) transfers heat from the interior of the motor 14 into the cooling fluid, which transports the heat out of the drive assembly 24.

[0040] The radially inner and outer jacket housing members 72 and 74 may be sealingly connected together by any suitable means to prevent leakage of cooling fluid. For example, the jacket housing members 72 and 74 may be welded or brazed together.

[0041] The cooling jacket 70 seats against the inner surface 32 of the support structure 12. Preferably, substantially all of the radially outer surface, shown at 82, of the cooling jacket 70 is in contact with the radially inner surface 32 of the support structure 12, to assist with heat transfer out of the cooling jacket 70.

[0042] By having the cooling jacket 70 be positioned within the support structure 12 (which acts as a motor housing) the cooling jacket 70 is better positioned to receive heat from the operation of the motor 14 and therefore to transport heat out of the motor 14. By contrast, a cooling jacket that is mounted to the exterior of the support structure 12 would only receive heat that is conducted through the support structure 12. It is, however, nonetheless within the scope of some aspects of the invention for a cooling jacket to be provided on the exterior of the support structure 12 instead of on the interior of the support structure 12.

[0043] Making the cooling jacket 70 as a self-contained unit is advantageous in that the cooling jacket 70 may be made and tested prior to assembly of the motor 14. Thus, any defective cooling jackets 70 can be removed before being incorporated into the motor 14. A further, related advantage is that the cooling jacket 70 can be made by another party and shipped to the motor assembler, for example, or to the assembler of the wheel assembly, pre-tested and pre-filled with cooling fluid, thereby facilitating the motor assembly process. It is nonetheless within the scope of selected aspects of the present invention, however, for the cooling jacket 70 to not be self- contained and to instead include a jacket housing member that is sealingly connected to the support structure 12 (eg. by welding) to enclose an interior channel structure for the transport of cooling fluid. [0044] The stator 50 may be mounted directly to the radially inner surface of the cooling jacket 70 shown at 84. The stator 50 is a significant source of heat in the electric motor 14. By having the stator 50 in direct connection with the cooling jacket 70, the cooling jacket 70 is positioned to receive more heat from the stator 70, than would be a cooling jacket that is positioned on the exterior of the support structure 12, and is therefore better able to transport more heat away from the stator 50. The stator 50 may have an interference fit with the cooling jacket 70, and thermally conductive grease or the like may be provided between them, which provides for good heat transfer out of the stator 50 and also assists in reducing the amount of vibration in the stator 50. However, the high force used to hold the stator 50 to the support structure 12 via the fasteners 58 lessens whatever additional benefit is provided by having a high amount of interference between the stator and the cooling jacket. As a result, a smaller interference fit can be used, which in turn means that lower stresses are imposed on the cooling jacket 70. As a result, the cooling jacket may be made thinner, which improves heat transfer into it from the stator 50.

[0045] The rotor 52 includes rotor laminations 86, a plurality of rotor magnets 88, a rotor hub 90 and inboard and outboard balance pieces 92 and 94. The balance pieces 92 and 94 are connected to each other via rotor fasteners 68 and clamp the rotor components together.

[0046] The rotor hub 90 supports the other rotor components and is itself supported at an inboard end on the inner surface 32 of the support structure through a first motor bearing 96. In particular, the portion of the inner surface 32 on which the bearing 96 is engaged may be the wall of an aperture 98 on the inboard cover 30. The first motor bearing 96 may be any suitable type of bearing, such as, for example, a tapered roller bearing. A nut clamp 100 threadably mounts to a threaded portion shown at 102 on the inboard cover 30, and is adjustable in its axial position via the threaded engagement with the inboard cover 30. This adjustability permits the nut clamp 100 to be used to adjustably engage the bearing 96 and control the amount of endplay present therein.

[0047] The rotor hub 90 has an outboard end 106 whereat it operatively engages the gearbox 16. The gearbox 16 may be any suitable type of gearbox, such as, for example, a planetary gearbox. The gearbox 16 includes a sun gear 108 which mounts to the outboard end 106 of the rotor hub 90 by way of a splined connection or any other suitable connection so that the rotor 52 drives the sun gear 108. The gearbox 16 further includes a set of planet gears 1 10, a planet carrier 1 12 and a ring gear 1 14. The ring gear 1 14 is fixedly mounted to the inner surface 32 of the support structure 12 via fasteners 1 16, and is supported in the interior 38 thereof.

[0048] The planet carrier 1 12 has an inboard end 1 18 and an outboard end 120. The inboard end 1 18 includes a radially inner surface 122 and a radially outer surface 124. The radially outer surface 124 is supported on the inner surface 32 of the support structure 12 by way of a bearing 125, which may be a tapered roller bearing, similar to the bearings 96. The bearing 125 constitutes a first gearbox bearing.

[0049] The outboard end 106 of the rotor hub 90 is supported on the radially inner surface 122 of the planet carrier 1 12 by way of a bearing 126. The bearing 126 may be a tapered roller bearing, similar to the first motor bearing 96 and similar to the first gearbox bearing 125. The bearing 126 constitutes a second motor bearing, and serves to center the rotor hub 136 and the planet carrier 1 12 relative to each other, which in turn assists in centering the sun gear 108 relative to the planet gears 1 10. Adjustment of the nut clamp 100 assists in removing the endplay in the bearing 126. [0050] An optional lubricant transfer conduit 130 (Figure 2) extends between a central aperture 132 on the planet carrier 1 12 and a central aperture 134 on the rotor hub 90 to maintain lubricant flow between them, and specifically to permit fluid flow from the planet carrier 1 12 into the rotor hub 90. Without the transfer conduit 130, the lubricant (eg. oil) that leaves the central aperture 132 on the planet carrier would fall vertically and as a result not much lubricant would be transferred to the rotor hub. The transfer conduit 130 may be made from any suitable material, such as mild steel or aluminum and may be press-fit into the apertures 132 and 134. As a result, if the conduit 130 is damaged during assembly of the wheel assembly 10 it is unlikely to break or to cause a malfunction in the wheel assembly. [0051] The planet carrier 1 12 constitutes a gearbox output member, and has a splined connection to a wheel hub 136 that makes up part of the wheel 20. The wheel hub 136 is supported on the inner surface 32 of the support structure 12 by way of a bearing 137, which may also be a tapered roller bearing. The bearing 137 constitutes both a wheel bearing and a second gearbox bearing.

[0052] A fastener, such as a nut 138 connects to a threaded surface 139 on the planet carrier 1 12 and thereby holds the wheel hub 136 thereon. The nut 138 is adjustable axially due to its threaded connection with the planet carrier 1 12. Adjustment of the nut 138 controls the position of the wheel hub 136 so as to control the amount of endplay in the bearing 137. Adjustment of the nut 138 also controls the amount of endplay in the bearing 128.

[0053] A separation member shown at 140 separates a gearbox chamber 142 from at least some of the motor 14. At least a portion of the gearbox 16 (in the embodiment shown, all of the gearbox 16) is positioned in the gearbox chamber 142. The gearbox chamber 142 contains lubricant for the gearbox 16. The separation member 140 in the embodiment shown, mounts sealingly at its outer end to the inner surface 32 of the support structure 12 via fasteners 1 16 which also hold the ring gear 1 14 to the support structure 12. At its inner end, a seal 143 is provided between the separation member 140, which is stationary, and the rotating sun gear 108. The separation member 140 forms an inboard end of the gearbox chamber 142. A seal arrangement shown at 144 is provided between the wheel hub 136 and the support structure 12 to seal an outboard end of the gearbox chamber 142. Thus, lubricant in the gearbox chamber 142 can lubricate components including the sun gear 108, the planet gears 1 10, the ring gear 1 14 and the bearings 126, 128 and 137.

[0054] Referring to Figure 2, the wheel 20 further includes a spider and rim portion 146, which are configured to hold a tire (not shown) and which may be formed in one piece (eg. a casting). The wheel 20 may be any suitable size wheel, such as, for example, a 15" wheel. A plurality of wheel fasteners 148 (eg. bolts 150 and nuts 152) hold the wheel hub 136 to the spider and rim portion 146. The wheel fasteners 148 also hold a brake disk 154 together with the wheel 20. The brake disk 154 forms part of the brake 18 and may be any suitable type of brake disk. In the embodiment shown the brake disk 154 is vented. The brake disk 154 is held in a region about the outboard portion 46 of the outer surface 34 of the support structure 12. This region has sufficient room for the components of the brake 18 and an optional parking brake shown at 155.

[0055] A caliper 156 (best seen in Figure 8) which also forms part of the brake 18 mounts to the support structure 12 and is positioned for clamping the brake disc 154 when it is desired to stop the vehicle. The caliper 156 includes a first, inboard, caliper portion 158 and a second, outboard, caliper portion 160. Referring to Figure 4, the first caliper portion 158 includes a first, inboard, caliper housing portion 162, which defines first and second inboard fluid chambers 164, first and second inboard pistons 166, first and second inboard piston seals 168 for sealing between the pistons 166 and the walls of the fluid chambers 164, and a first, inboard, brake pad 172, which includes a support 174 and a lining 176. In the embodiment shown, the first caliper housing portion 162 is integrally formed with the support structure 12 and extends outwards from the outer surface 34 thereof (preferably from the transition portion 48 of the outer surface 34). Thus the first and second fluid chambers 164 are bores that are directly formed in the support structure 12. A brake fluid conduit arrangement 178 is provided to transport brake fluid to and from the fluid chambers 164. The brake fluid conduit arrangement 178 may be provided by an external conduit that feeds brake fluid to a port on the first brake housing 162. The external conduit could be, installed in a groove on the support structure 12 so as to remain substantially flush with the out surface 34 o the support structure 12. Alternatively, the conduit arrangement 178 may be provided internally to the support structure 12 (eg. by drilling conduit passages directly in the support structure 12). [0056] The second, outboard caliper portion 160 mounts to the support structure 12 via a plurality of caliper fasteners 180 (Figure 8). The caliper portion 160 includes a second, outboard, housing portion 182, which defines first and second outboard fluid chambers 184 (only one fluid chamber 184 is shown in the figures). The second housing portion 182 and the first housing portion 162 together make up a brake caliper housing 185. The second, outboard caliper portion 160 further includes, first and second outboard pistons 186 as shown in Figures 7a and 7b, (only one is shown in the figures), first and second inboard piston seals 188 for sealing between the pistons 186 and the walls of the fluid chambers 164, and a second, outboard, brake pad 192, which includes a support 194 and a lining 196. A brake fluid conduit arrangement 198 is provided to transport brake fluid to and from the fluid chambers 164. The brake fluid conduit arrangement 198 may be in the form of external conduits which connect from a port on the first brake housing 162 to an internal fluid passageway in the housing 182.

[0057] When it is desired to brake the vehicle, the brake fluid is brought up to a suitable fluid pressure to urge the pistons 166 and 168 against the brake pads 172 and 192 to urge the brake pads 172 and 192 into engagement with the brake disk 154 with a selected braking force. [0058] To replace the pads 172 and 192, the nuts 152 are removed and the spider and rim portion 146 is removed, thereby exposing the brake 18. The outboard caliper portion 160 is then removed from the support structure 12 by removing the fasteners 180. This permits the replacement of the brake pad 192. This permits the brake disk 154 to be removed from the wheel hub 136 thereby exposing the inboard brake caliper portion 158 so that the inboard brake pad 172 can be removed and replaced.

[0059] Optionally, a feature can be provided to permit the brake pads 172 and 192 to be replaced without removing the outboard caliper portion 160 and the brake disk 154. For example, in such an optional embodiment, an access aperture shown at 200 in Figure 9 can be provided in a suitable position in the brake caliper housing 185, (eg. directly radially outwardly from the brake pads 172 and 192). In the embodiment, shown, this would be in the outboard brake caliper housing portion 182. Any fasteners 180 that are blocking access to the brake pads 172 and 192 through the access aperture 200 are removed. In the embodiment shown, the centre fastener 180 is removed. If the linings of the pads 172 and 192 are sufficiently worn down, the pads 172 and 192 can be advanced axially towards the brake disk 154 if necessary and then slid radially outwardly through the access aperture 200 to be removed. New brake pads 172 and 192 can be slid in radially through the access aperture on either side of the brake disk 154 and slid axially as necessary into place to be engaged by the pistons 166 and 186. The removed one or more fastener 180 that blocked the aperture 200 can then be reinserted to reblock the aperture 200 preventing the pads 172 and 192 from inadvertently leaving their positions during use. In this embodiment, the centre fastener 180 may be referred to as a removable access aperture blocker. Then the spider and rim portion 146 (Figure 2) of the wheel 20 can be remounted to the wheel hub 136.

[0060] It will be understood that, while the caliper 156 engages each of the pads 172 and 192 with two pistons, it is alternatively possible to provide a caliper that only uses one piston on each side to engage each of the pads 172 and 192. Alternatively, the caliper 156 could be configured to engage the pads 172 and 192 with another other suitable number of pistons.

[0061] Reference is made to Figure 10, which shows a vehicle 208 in which the wheel assembly 10 is installed. The vehicle 208 may have any suitable number of the wheel assemblies 10 installed therein. For example, the vehicle 208 may include a wheel assembly 10 in place on both sides at the front and at both sides at the rear, (ie. for a total of four wheel assemblies 10). In an alternative example, the vehicle 208 may only have wheel assemblies 10 at both sides at the front of the vehicle 208. In another alternative example, the vehicle 208 may have wheel assemblies 10 only at both sides in the rear of the vehicle 208. [0062] The vehicle 208 shown in Figure 10 includes a chassis 219, four motor control units (MCUs) 201 (ie. one per motor 14) and a vehicle control unit (VCU) 203, which communicates with each of the MCUs 201 . Together the VCU 203 and the MCUs 201 will all collectively be referred to as a controller 202. The vehicle 208 preferably employs regenerative braking using the controller 202. As is well known in the art, regenerative braking constitutes using operating the driven wheels' electric motors as generators to slow a vehicle down and to use the kinetic energy of the vehicle to charge the vehicle's battery pack (shown in Figure 10 at 210). For the vehicle 208 shown in Figure 10, regenerative braking is the primary means of braking, and is used by the controller 202 to control the total four-wheel adhesion of the vehicle 208. Secondary braking, which is provided in addition to the regenerative braking, is provided by the brake 18. In Figure 10, the wheels of the vehicle 208 are shown twice, for the purpose of clearly showing the components of the primary braking system (using regenerative braking) separately from the secondary braking system (using the brake 18). The vehicle 208 includes a brake pedal 206 that is biased by a biasing member 207, which may be, for example, a compression spring, to a rest position. The brake pedal 206 is movable from the rest position through a range of travel. A sensor 209 is positioned to sense the position (eg. the angular position) of the brake pedal 206 and to communicate the position of the brake pedal 206 to the controller 202 (in the embodiment shown it is transmitted to the VCU 203). The controller 202 (again the VCU 203 specifically in the embodiment shown), receives other input signals from various points in the vehicle 208, including, for example, signals from speed sensors shown at 21 1 , as well as signals from optionally included systems such as an anti-lock braking system, a traction control system, sensors to detect cornering loads and collision avoidance systems such as lane anti-drift systems, adaptive cruise control systems and the like. The controller 202 sends signals to the individual motors 14 to determine the amount of regenerative braking to apply based on the inputs described above. [0063] In addition to the electrical connection between the brake pedal 206 and the controller 202 for controlling the regenerative braking of the vehicle 208, the brake pedal 206 is operatively connected to a braking system 213 that controls the brakes 18. As can be seen in Figure 10, the wheel assemblies 10 at the front of the vehicle 208 (ie. driving the front wheels shown at 20a and 20b) include brakes 18. However, the wheel assemblies 10 at the rear of the vehicle 208 (ie. driving the rear wheels shown at 20c and 20d) may do without hydraulic brakes. This is because the regenerative braking provided from the motors 14 at the rear wheels 20c and 20d may be sufficient to handle the reduced braking forces that are typically needed on rear wheels of vehicles. During braking the center of mass of the vehicle shifts forwardly and so the amount of loading on the front wheels and the braking force required to stop the front wheels are typically higher than they are on the rear wheels. The braking system 213 may be any suitable type of braking system, such as a hydraulic braking system, which incorporates a vacuum booster 214, a master cylinder 215, and a hydraulic conduit 217 that is part of the hydraulic conduit system 178 which leads to the calipers 156 at each wheel 20a and 20b.

[0064] Optionally, the vehicle 208 may be configured to avoid the use of the brake 18 and uses only regenerative braking in situations where that is sufficient, and uses the braking system 213 when the driver of the vehicle appears to want or need more braking than would be provided solely by the regenerative braking system. To this end, a selective lost motion hydraulic cylinder 216 may be provided to operatively connect the brake pedal 206 to the braking system 213. The hydraulic cylinder 216 functions to prevent actuation of the brakes 18 during an initial amount of travel of the brake pedal 206, if the brake pedal 206 is depressed at a sufficiently slow speed, and to incorporate actuation of the brakes 18 if the brake pedal 206 is depressed beyond the initial amount of travel. Furthermore, the hydraulic cylinder 216 is configured to incorporate actuation of the brakes 18 substantially immediately (ie. even in the initial amount of travel of the brake pedal 206) if the driver depresses the brake pedal 206 sufficiently quickly (indicating that the driver wants the vehicle 208 to stop quickly).

[0065] As a result, a significant amount of the kinetic energy of the vehicle 208 is captured and stored in the vehicle's battery pack 210. Additionally, the life of the brake pads 172 and 192 (Figure 7a and 7b) is extended since they are not used in every braking situation, and when they are used, the regenerative braking still consumes at least some portion of the kinetic energy of the vehicle 208 that would otherwise have to be handled by the brakes 18. [0066] The hydraulic cylinder 216 includes a housing 220, a piston 222 and hydraulic fluid in the housing 220. The hydraulic cylinder 216 includes a fluid passageway 223 between a first housing portion 224 on a first side of the piston 222 and a second housing portion 228 on a second side of the piston 230. The fluid passageway 223 may be, for example, an aperture that passes through the piston 222. The hydraulic fluid shown at 226 has a first viscosity during movement of the piston 222 against the hydraulic fluid 226 at a first piston speed. The hydraulic fluid 226 has a second viscosity that is higher than the first viscosity during movement of the piston 222 against the hydraulic fluid 226 at a second piston speed that is higher than the first piston speed. [0067] The brake pedal 206 is operatively connected to a first end 229 of the hydraulic cylinder 216 which is on one of the piston 222 and the housing 220, and a second end 230 of the hydraulic cylinder 220 is on the other one of the piston 222 and the housing 220, and is operatively connected to the brake caliper 156. For example, in the embodiment shown the second end 230 is connected to a push rod for the vacuum booster 214. In the embodiment shown, the first end 229 is on the piston 222 and the second end 230 is on the housing 220.

[0068] Movement of the brake pedal 206 from a first brake pedal position (Figure 14a) to a second brake pedal position (Figure 14b) at a first pedal speed causes movement of the first end 229 of the hydraulic cylinder 216 at a first speed between a first position for the first end 229 and a second position for the first end 229. This, in turn, causes relative movement of the piston 222 through the hydraulic fluid 226 at a first relative speed (which may be referred to as a first piston speed) such that a first volume of hydraulic fluid 226 flows through the fluid passageway 223 from the first housing portion 224 to the second housing portion 228. The piston 222 generates a force on the housing 220 through the fluid in the first housing portion 224 even though the piston 222 is moving relative to the housing 220. The housing 220, however, is restrained from movement unless urged with at least a selected force. The force exerted on the housing 220 during the piston's movement is too small to cause movement of the housing 220 and so no actuation of the brake caliper 156 takes place.

[0069] The second position of the brake pedal 206 corresponds to the bottoming out of the piston 222 in the housing 220 so that the piston 222 is positively engaged with the housing 220. Thus, any further movement of the brake pedal 206 past the second brake pedal position causes movement of the housing 220, which thereby causes movement of the push rod into the vacuum booster 214, which in turn causes actuation of the brake calipers 156. The degree of actuation of the brake calipers 256 depends on how far the brake pedal 206 is depressed past the second brake pedal position. Thus, to summarize, when the brake pedal 206 is moved from a first (rest) position to a second position at the first brake pedal speed, the hydraulic cylinder 216 acts as a lost motion mechanism which prevents actuation of the brake caliper 156 so that braking is only carried out using the regenerative braking system.

[0070] Movement of the brake pedal 206 at a second, faster speed from the first brake pedal position to the second brake pedal position causes movement of the first end 229 of the hydraulic cylinder 216 at a second speed between the first position for the first end 229 and the second position for the first end 229. Movement of the first end 229 at the second speed between the first position and the second position urges the piston 222 against the hydraulic fluid 226 in the first housing portion 224 at the second speed (which may be referred to as the second piston speed). At this second piston speed, the effective viscosity of the fluid 226 increases such that a second volume of hydraulic fluid 226 that is smaller than the first volume of hydraulic fluid 226 flows through the fluid passageway 223 from the first housing portion 224 to the second housing portion 228. As a result of the reduced volume of fluid 226 that passes through the fluid passageway 223, the piston 222 exerts a second force that is higher than the first force, on the housing 220 and therefore on the second end 230 of the hydraulic cylinder 216. The second force is sufficiently high to overcome the resistance of the housing 220 and so the housing 220 is moved, which in turn moves the push rod into the vacuum booster 214, which in turn causes actuation of the brake caliper 156.

[0071] The volume of fluid 226 that passes through the fluid passageway 223 (ie. the second volume of fluid 226) could be approximately zero, depending on such factors as the fluid's effective viscosity and the size and length of the fluid passageway 223. In a case where the volume of fluid 226 that passes through the fluid passageway 223 is approximately zero, it means that movement of the first end 229 causes approximately immediate movement of the second end 230 towards actuation of the brake caliper 156. In other words the properties of the hydraulic fluid 226 and the fluid passageway 223 may be such that there is substantially no lag between movement of the first end 229 (when moved at the second speed), and movement of the second end 230. [0072] Figure 15a is a graph that shows the relationship between pedal and torque applied to arrest rotation of the wheel 20. Three curves are shown. The curve shown at 300a corresponds to the braking torque provided by the regenerative braking system. The curve 300b corresponds to the braking torque provided by the hydraulic braking system 213 (Figure 10) when the brake pedal is depressed at the first pedal speed discussed above (ie. slowly). The curve 300c corresponds to the total braking torque (ie. provided by both systems). As can be seen, for the first amount of pedal travel (which may correspond, as shown, to somewhere between 5 and 10 degrees of pedal travel) the regenerative braking system is the only one providing any braking torque on the wheel 90. The amount of braking torque provided by the regenerative braking system increases with the amount that the pedal is depressed. If the brake pedal 206 (Figure 10) is moved past the aforementioned first amount of pedal travel, the braking torque provided by the hydraulic braking system 213 (Figure 10) increases. This graph illustrates the relationship between angular pedal travel and braking torque during typical city driving conditions. In other words, during typical city driving conditions, the driver depresses the brake pedal 206 sufficiently slowly that the hydraulic braking system 213 is delayed until between 5 and 10 degrees of brake pedal travel (more specifically between 7 and 8 degrees of travel). Moreover, during typical city driving conditions, a driver calls upon the brakes to generate between about 0.1 g and 0.25g of deceleration. As shown in the graph in Figure 15a, this means that the vast majority of braking done during city driving involves only regenerative braking and very little hydraulic braking is carried out. For a typical city driving situation, the braking could be approximately 99% regenerative. Thus, there is a greater amount of recaptured kinetic energy from the vehicle as compared to an electric vehicle with a hydraulic braking system that is invoked immediately (ie. with no lost motion mechanism). It will also be noted that, in the event of failure for some reason of the hydraulic braking system 213, the regenerative braking system is capable of generating up to approximately 0.6g of deceleration on its own.

[0073] Figure 15b is a graph that shows the relationship between pedal and torque applied to arrest rotation of the wheel 20 when the driver depresses the brake pedal fast enough to cause the effective viscosity change in the hydraulic fluid 226 in the selective lost motion hydraulic cylinder 216 (eg. in a panic braking situation). Three curves are again shown. The curve shown at 302a corresponds to the braking torque provided by the regenerative braking system, and may be identical to the curve 300a in Figure 15a in this exemplary embodiment. The curve 302b corresponds to the braking torque provided the hydraulic braking system 213 when the brake pedal 206 is depressed at the second pedal speed (ie. quickly). The curve 302c corresponds to the total braking torque (ie. provided by both systems). As can be seen, the hydraulic braking system 213 is invoked at a lower brake pedal angle, (eg. approximately 3 degrees) than in the graph shown in Figure 15a. As a result, a greater total braking torque is generated over the early range of brake pedal travel angles, which assists the vehicle 208 in stopping earlier. For example, when the driver pushes the brake pedal 206 quickly, the total deceleration provided by the vehicle 208 at 9 degrees of brake pedal travel is about 0.55g (as shown in Figure 15b), whereas it is only about 0.3g at 9 degrees of pedal travel if the driver depresses the brake pedal 206 slowly (as shown in Figure 15a). [0074] While the brake torque curve 302a for the regenerative braking system is the same in Figure 15b as the curve 300a in Figure 15a in this exemplary embodiment, it is optionally possible to provide a sensor to detect when panic braking is taking place which is used by the VCU to alter (ie. increase) the brake torque applied by each of the electric motors 14 for a given pedal position.

[0075] The threshold speed below which the first end 229 of the cylinder 216 can be moved without causing actuation of the brake caliper 156 (ie. thereby using regenerative braking solely) may be selected so that regenerative braking accounts for a significant portion of the time during typical braking events during typical city driving use of the vehicle 208.

[0076] As can be seen in Figures 15a and 15b, the amount of braking provided by the motors 14 is a significant portion of the total braking torque applied to the wheels 20 throughout a significant range of pedal positions during both non-panic braking (Figure 15a) and panic braking (Figure 15b) situations. By programming the controller 202 appropriately, an anti-lock braking capability may be provided by controlling the current to the electric motors, and thus without the need for valves and dedicated hydraulic lines. More specifically, the controller 202 may be programmed to receive data from each of the wheel speed sensors 21 1 and to use that data to determine if there is impending lock-up at any wheel 20, and to adjust the braking torque to apply at each motor 14 on each wheel 20 accordingly, so as to prevent lock up at each wheel. Providing an anti-lock braking system by adjusting the brake torque applied to the individual motors 14 may be less expensive and may involve less additional hardware than would normally be required for a typical hydraulic anti-lock braking system. The brake torque may be adjusted with any suitable frequency, such as 20 times per second. Such anti-lock braking can be effective even if the vehicle 208 only includes two driven front wheels 20 or two driven rear wheels 20.

[0077] Initially, the controller 202 may be preprogrammed to apply the braking torque according to a map, using the vehicle geometry, weight transfer that is expected to take place, steering wheel angle, and other information. As the vehicle 208 slows during a braking event, the controller 202 may adjust the torque applied to each individual motor 14 based on updated information on the vehicle such as speed and steering wheel angle. [0078] Additionally, the controller 202 may be programmed to control the motive torque applied to each motor 14 during acceleration of the vehicle 208. Using the wheel speed sensors 21 1 and comparing the wheel speeds of the individual wheels 20, it is possible for the controller 202 to determine whether wheelslip is taking place at each individual wheel. Using this information, the controller 202 may reduce the accelerative torque independently at each individual wheel 20 as necessary in order that each wheel maintains traction. Providing independent traction control at each wheel 20 without complex mechanical linkages is advantageous in that it provides improved performance at relatively little cost and complexity. [0079] Figure 16 is a graph with a curve 304 illustrating the relationship between brake pedal travel and brake pedal force, and also shows the amount of total deceleration provided at selected points along the curve 304. As can be seen, as the brake pedal 206 travels further into its range of travel, the amount of force required to depress it further increases. A rectangle shown at 306 illustrates the portion of the brake pedal travel that is used during typical city driving. A rectangle shown at 308 show the brake pedal travel required to meet certain federal brake torque requirements in the United States.

[0080] In the event of a failure of the regenerative braking system it will be noted that the hydraulic brake 18 may be configured to stop the vehicle 208 within a selected stopping distance from a selected speed, so as to meet certain brake performance requirements, such as those mandated by FMVSS (Federal Motor Vehicle Safety Standards) in the United States. It will be understood that in the event of a failure of the regenerative braking system, the driver would have to depress the brake pedal further to achieve a selected brake torque than would be required if the regenerative braking system were operational.

[0081] The brake pedal 206 may be configured so that beyond an initial 300N of force applied to the brake pedal 206, it permits 1 mm of travel for each additional 100N of force applied thereto.

[0082] As noted above, as a result of the relative great amount of regenerative braking used in typical city driving, less wear may be incurred by the brake disk 154 and the pads 172 and 192 than for a vehicle where hydraulic braking is invoked substantially immediately (ie. without a lost motion mechanism). To take advantage of this reduced wear, the brake disk 154 and the brake pads 172 and 192 may be made relatively thin for space efficiency, without unduly reducing their effective lives in terms of distance driven by the vehicle. Nonetheless, even though thinner than a brake in a typical vehicle, the brake 18 is capable of meeting jurisdictional performance requirements, such as those described in FMVSS-135. [0083] Referring to Figures 2 and 5, the brake disk 154 may be generally hat-shaped and may include an axially extending radially inner surface 234 that constitutes a drum surface which is part of the optional parking brake 155. The parking brake 155 further includes a shoe assembly 238 that may include any suitable number of shoes 240 (Figure 1 1 ). In the embodiment shown, two shoes 240 are shown, and are identified at 240a and 240b. The shoe assembly 238 further includes a shoe support 242, a shoe actuation linkage 244, and an optional shoe adjustment mechanism 246. The shoes 240 are each pivotally mounted at one end to the shoe support 242. The shoe actuation linkage 244 may be any suitable linkage known in the art. In the embodiment shown, the linkage 244 includes a shoe actuation lever 248 and a shoe actuation link 250 on which the lever 248 pivots. A cable 252 may connect the shoe actuation lever 248 to a lever (not shown) in the passenger compartment of the vehicle 208. Actuation of the cable 252 pulls the lever 248 which pivots about the pivot axis 254 (Figure 12) and drives the first shoe 240a (Figure 1 1 ) in a first direction towards engagement with the drum surface 234. The pivoting motion of the lever 248 pushes the link 250 in a second, opposing direction, which drives the second shoe 240b towards engagement with the drum 234. A releasable position-locking structure may be provided in the passenger compartment permitting the shoes 240 to be held in engagement with the drum surface 234. The shoe adjustment mechanism 246 may be any suitable mechanism known in the art for adjusting the at-rest (ie. unactuated) positions of the shoes 240. In Figure 12, the lever 248 is shown in both its unactuated position (in solid line) and actuated positions (in dashed outline). The routing of the cable 252 may be as shown in Figure 17, in which the cable 252 passes through a passageway 255 in the shoe support 242 and passes along the exterior surface of the support structure 12 as shown in Figure 17.

[0084] In the embodiment shown in Figure 10, the parking brake 155 is shown at being provided on the rear wheels 20c and 20d even though a hydraulic braking system 213 is not provided for those wheels 20c and 20d. It may be that the brake disc 154 is provided so that it provides a drum surface for the parking brake 155. Alternatively it may be that an alternative drum member may be provided, which would be smaller, lighter and less expensive than the brake disk 154. Alternatively, the parking brake 155 could be provided on the brake disks 154 on the front wheels 20a and 20b instead of being at the rear wheels 20c and 20d.

[0085] Referring to Figure 13, the outer face of the inboard cover 30 is shown at 256 and may have a set of studs 258 extending outwardly therefrom that are configured for mounting to a standard flange from a standard rigid axle (eg. at the rear of some vehicles). Additionally, the outer face 256 may further include additional studs extending therefrom, such as studs 260 shown proximate the upper edge of the inboard cover 30. In embodiments wherein the wheel assembly 10 is to have a suspension member connected thereto, an adapter 262 may be mounted to the studs 258 and 260 for providing a mounting location for the suspension member (not shown). Nuts 261 and 263 are provided for holding the adapter 262 to the studs 258 and 260. The adapter 262 may easily be manufactured according to the specifications of the customer. Thus, the wheel assembly 10 can be customized to meet the needs of different customers with different suspension mounting requirements. The adapter 262 is shown mounted to the inboard cover 30 in Figure 1 b.

[0086] Referring to Figure 2, it will be noted that the portion of the support structure 12 which supports the motor 14 has a diameter and wall thickness that are selected to provide a selected resistance to deflection, thereby reducing the likelihood of bringing the rotor 52 and the stator 50 out of alignment from each other when the vehicle 208 encounters a bump or other road imperfection. As a result, the gap between the rotor 86 and stator 54 may remain relatively constant, thereby potentially improving the operating life of the motor 14. Furthermore, the portion of the support structure 12 which supports the wheel 20 has a diameter and a wall thickness that are selected to provided a selected resistance to deflection which may be less than that of the portion supporting the motor 14. As a result, impacts of the wheel 20 on road imperfections may be absorbed in that part of the support structure without necessarily being transmitted fully to the portion of the support structure 12 supporting the motor 14. [0087] During use, the load path through the wheel assembly 10 is such that the load passes into the spider and rim portion 146 of the wheel 20, from there into the wheel hub 136 and gearbox output member (ie. the planet carrier 1 12), and from there through the bearings 125 and 137 into the support structure 12. [0088] It will be noted that not all of the structure shown in the figures need be provided in order to achieve some aspects of the invention. For example, the support structure 12 which is advantageously formed with one of the brake caliper housings and fluid chambers directly therein need not also have the feature of supporting the wheel 20, the gearbox 16 and the motor 14 all on its inner surface 32. In another example, configuring the brake linkage to include the selective lost motion hydraulic cylinder 216 is advantageous regardless of whether one of the brake caliper housings and fluid chambers are formed directly in the support structure 12. As yet another example, the advantages of forming the inboard brake caliper housing directly in the support structure are achieved regardless of whether the motor 14 is a radial flux motor or an axial flux motor, and regardless of whether a gearbox is included with the wheel assembly or not. In yet another example, the selective lost motion mechanism that is provided so that the regenerative braking is used solely for at least some initial amount of brake pedal travel does not necessitate the use of a hydraulic braking system. Any suitable mechanical type braking system incorporating a rotating member that rotates with the wheel and a braking member that arrests rotation of the rotating member may be connected to the brake pedal through the selective lost motion mechanism.

[0089] It will be noted that the wheel assembly 10 shown and described may be used at any suitable number of wheels of the vehicle. In other words, the vehicle 208 may include any suitable number of driven wheels each using the wheel assembly 10. For example, the vehicle may have one driven wheel and may thus include one wheel assembly 10. Alternatively, for example, the vehicle may include two driven wheels, each using a wheel assembly 10. Alternatively, for example, the vehicle may include four driven wheels each using a wheel assembly 10.

[0090] While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.

Claims

CLAIMS:

1 . A wheel assembly for a vehicle, comprising:

a support structure;

a wheel rotatably supported by the support structure for rotation about a wheel axis;

an electric motor including a stator and a rotor, wherein the stator is supported by the support structure, and wherein the rotor is operatively connected to the wheel; and

a brake including a brake disk connected for rotation with the wheel, and a brake caliper including an outboard caliper portion and an inboard caliper portion, wherein the inboard caliper portion includes at least one inboard fluid chamber, at least one inboard piston movable within the at least one inboard fluid chamber, and an inboard brake pad, wherein the at least one inboard fluid chamber is contained in the support structure, wherein the at least one inboard fluid chamber and the inboard brake pad are positioned such that introducing fluid at a selected pressure into the at least one inboard fluid chamber urges the inboard brake pad against an inboard side of the brake disk,

wherein the outboard caliper portion is mounted to the support structure and includes at least one outboard fluid chamber, at least one outboard piston movable within the at least one outboard fluid chamber, and an outboard brake pad, which are positioned such that introducing the fluid at the selected pressure into the at least one outboard fluid chamber urges the outboard brake pad against an outboard side of the brake disk.

2. A wheel assembly as claimed in claim 1 , wherein the brake caliper includes a brake caliper housing which houses the at least one inboard and outboard fluid chambers, the at least one inboard and outboard pistons and the inboard and outboard brake pads, wherein the brake caliper housing has an access aperture through which the inboard and outboard brake pads can be removed from the brake pad housing, and an access aperture blocker, which is positionable to block the access aperture and thereby prevent the removal of the inboard and outboard brake pads from the brake caliper housing, and which is removable from the access aperture so as to permit the removal of the inboard and outboard brake pads therethrough without the removal of the brake disk from the wheel.

3. A wheel assembly as claimed in claim 1 , wherein the access aperture is directly radially outward from the inboard and outboard brake pads.

4. A wheel assembly as claimed in claim 1 , wherein the support structure includes at least one first fluid conduit extending therethrough to the at least one inboard fluid chamber.

5. A vehicle, comprising:

a chassis;

a plurality of wheels supporting the chassis, wherein the plurality of wheels includes a driven wheel;

an electric motor operatively connected to the driven wheel;

a battery pack for use in powering the electric motor;

a controller;

a mechanical brake that is actuatable to arrest rotation of the driven wheel, wherein the mechanical brake includes a rotating member that is associated with the driven wheel and a braking member that is movable to engage the rotating member frictionally to arrest rotation of the rotating member; and

a brake linkage operatively connecting a brake pedal to the braking member, wherein the brake linkage includes a hydraulic cylinder, wherein the hydraulic cylinder includes a housing, a piston and a hydraulic fluid in the housing, wherein the hydraulic cylinder includes a fluid passageway between a first housing portion on a first side of the piston and a second housing portion on a second side of the piston, wherein the piston has an available stroke associated therewith, wherein the hydraulic fluid has a first viscosity during movement of the piston against the hydraulic fluid at a first piston speed and wherein the hydraulic fluid has a second viscosity that is higher than the first viscosity during movement of the piston against the hydraulic fluid at a second piston speed that is higher than the first piston speed,

wherein the brake pedal is operatively connected to a first end of the hydraulic cylinder which is on one of the piston and the housing, and wherein a second end of the hydraulic cylinder is on the other one of the piston and the housing and is operatively connected to the braking member,

wherein movement of the brake pedal from a first brake pedal position to a second brake pedal position at a first pedal speed causes movement of the first end at a first speed between a first position for the first end and a second position for the first end, wherein movement of the first end at the first speed between the first position for the first end and the second position for the first end causes relative movement between the piston and the hydraulic fluid against each other at the first piston speed such that a first volume of hydraulic fluid flows through the fluid passageway from the first housing portion to the second housing portion, and urges the second end to move with a first force that is too low to actuate the braking member,

and wherein movement of the brake pedal from the first brake pedal position to the second brake pedal position at a second pedal speed causes movement of the first end at a second speed between the first position for the first end and the second position for the first end, wherein movement of the first end at a second speed between the first position for the first end and the second position for the first end causes relative movement between the piston and the hydraulic fluid against each other at the second piston speed such that a second volume of hydraulic fluid that is smaller than the first volume of hydraulic fluid flows through the fluid passageway from the first housing portion to the second housing portion, and urges the second end of the hydraulic cylinder to move with a second force that is sufficient to actuate the braking member,

and wherein, during movement of the brake pedal from the first position to the second position at the first pedal speed, the controller operates the electric motor as a generator and generates electricity used to charge the battery pack.

6. A vehicle as claimed in claim 5, wherein movement of the first end at the first speed between the first position for the first end and the second position for the first end brings the first end to an end of the available stroke of the hydraulic cylinder, and wherein movement of the first end from the first position for the first end, past the second position for the first end to a third position for the first end causes movement of the second end, thereby actuating the braking member.

7. A vehicle as claimed in claim 6, wherein the cross-sectional size of the fluid passageway and the hydraulic fluid is selected to provide the brake pedal with a selected resistance to depression by a foot of a driver.

8. A vehicle as claimed in claim 5, wherein the second volume of hydraulic fluid is substantially zero.

9. A vehicle as claimed in claim 5, wherein a plurality of the wheels are driven wheels.

10. A drive assembly for a vehicle, comprising:

a support structure; an electric motor including a stator and a rotor, wherein the stator is supported by the support structure; and

a gearbox that is engaged by the rotor and that includes a gearbox output member, wherein the gearbox output member has a radially outer surface and a radially inner surface, wherein the gearbox output member is supported on the support structure by a first gearbox bearing on the radially outer surface,

wherein one end of the rotor is supported on the support structure by a first motor bearing, and a second end of the rotor is supported on the radially inner surface of the gearbox output member through a second motor bearing.

1 1 . A drive assembly as claimed in claim 10, wherein the gearbox output member is supported on the support structure by a second gearbox output member bearing.

12. A drive assembly as claimed in claim 10, wherein the second gearbox output member bearing is radially outside the common bearing.

13. A drive assembly as claimed in claim 10, wherein the gearbox is a planetary gearbox and the gearbox output member is a planet carrier from the planetary gearbox, and wherein a sun gear from the planetary gearbox is mounted to the rotor.

14. A drive assembly as claimed in claim 10, wherein the gearbox output member has an axially extending central aperture therein and the rotor has an axially extending central aperture therein, and a dowel connects between the central aperture of the rotor and the central aperture of the gearbox output member.

15. A wheel assembly for a vehicle, comprising: a support structure having an inboard end and an outboard end, wherein the support structure has an inner surface that defines an interior;

a motor including a stator and a rotor which are supported on the inner surface and which are contained in the interior;

a gearbox that is positioned outboard of the motor and is supported by the inner surface; and

a wheel that is driven by the motor through the gearbox, wherein the wheel is supported by the inner surface.

16. A wheel assembly as claimed in claim 15, wherein the support structure includes a main support structure portion and an inboard cover, wherein the motor, the gearbox and the wheel are all supported on the main support structure portion.

17. A wheel assembly as claimed in claim 16, wherein the inboard cover has an aperture therethrough defined by an aperture wall, wherein the aperture wall is part of the inner surface, wherein the aperture wall wherein one of the stator and the rotor is supported on the aperture wall.

18. A wheel assembly as claimed in claim 15, further comprising a separation member that mounts to the inner surface of the support structure and sealingly separates a gearbox chamber in which at least a portion of the gearbox is positioned from at least a portion of the motor, wherein the gearbox chamber contains lubricant for the gearbox.

19. A wheel assembly as claimed in claim 18, wherein the wheel is supported on the inner surface of the support structure by at least one wheel bearing, and wherein the gearbox includes a gearbox output member that is supported by at least one gearbox bearing, wherein the at least one wheel bearing and the at least one gearbox bearing are sealingly contained in the gearbox chamber.

20. A wheel assembly as claimed in claim 15, wherein the support structure has an exterior surface having an inboard portion, an outboard portion that is radially smaller than the inboard portion, and a transition portion between the inboard and outboard portions, wherein the wheel assembly further includes a brake disc that is positioned about the outboard portion of the support structure and that is connected to the wheel for rotation therewith, and a brake caliper that is mounted to the support structure and that is controllable, in use, to clamp the brake disk.

21 . A wheel assembly as claimed in claim 20, wherein the brake caliper includes an outboard caliper portion and an inboard caliper portion, wherein the inboard caliper portion includes an inboard fluid chamber and an inboard brake pad assembly, wherein the inboard fluid chamber extends outwardly from the transition portion and is contained in the support structure, and wherein the support structure includes at least one first fluid conduit extending therethrough to the inboard fluid chamber, wherein the inboard fluid chamber and the inboard brake pad assembly are positioned such that introducing fluid at a selected pressure urges the inboard brake pad assembly against an inboard side of the brake disk,

wherein the outboard caliper portion is mounted to the support structure and includes an outboard fluid chamber and an outboard brake pad assembly, which are positioned such that introducing the fluid at the selected pressure urges the outboard brake pad assembly against an outboard side of the brake disk.

22. A wheel assembly as claimed in claim 21 , wherein the brake disk includes an axially extending radially inner surface, wherein the wheel assembly further comprises a shoe assembly including at least one shoe and a shoe actuation linkage, wherein the shoe actuation linkage is actuatable to drive the at least one shoe into engagement with the radially inner surface of the brake disk.

23. A vehicle, comprising:

a chassis;

a plurality of wheels supporting the chassis, wherein the plurality of wheels includes a first driven wheel on a first side of the vehicle and a second driven wheel on a second side of the vehicle;

a first electric motor operatively connected to the first driven wheel;

a second electric motor operatively connected to the second driven wheel; a battery pack operatively connectable to power the first and second electric motors;

a first speed sensor positioned to sense the speed of the first wheel;

a second speed sensor positioned to sense the speed of the second wheel; and

a controller configured to receive signals from the first and second speed sensors, wherein, during braking of the vehicle, the controller is programmed to determine if there is impending lock-up at the first wheel based on signals from the first speed sensor and to control a first braking torque applied to the first electric motor to inhibit the first wheel from locking up, and to determine if there is impending lock-up at the second wheel based on signals from the second speed sensor and to control a second braking torque applied to the second electric motor to inhibit the second wheel from locking up.

24. A vehicle as claimed in claim 23, further comprising a first mechanical brake that is actuatable to arrest rotation of the first driven wheel, and a second mechanical brake that is actuatable to arrest rotation of the second driven wheel.

25. A vehicle as claimed in claim 23, wherein the plurality of wheels includes a third driven wheel on the first side of the vehicle and a fourth driven wheel on the second side of the vehicle;

a third electric motor operatively connected to the third driven wheel;

a fourth electric motor operatively connected to the fourth driven wheel; wherein the battery pack is operatively connectable to power the third and fourth electric motors;

a third speed sensor positioned to sense the speed of the third wheel; and a fourth speed sensor positioned to sense the speed of the fourth wheel; wherein the controller is configured to receive signals from the third and fourth speed sensors, wherein, during braking of the vehicle, the controller is programmed to determine if there is impending lock-up at the third wheel based on signals from the third speed sensor and to control a third braking torque applied to the third electric motor to inhibit the third wheel from locking up, and to determine if there is impending lock-up at the fourth wheel based on signals from the fourth speed sensor and to control a fourth braking torque applied to the fourth electric motor to inhibit the fourth wheel from locking up.

26. A vehicle as claimed in claim 23, wherein, during acceleration, the controller is programmed to determine if each of the wheels is incurring wheelspin and to control an accelerative torque to each electric motor independently to inhibit wheelspin at each wheel.

27. A vehicle, comprising:

a chassis;

four driven wheels,

four electric motors, wherein each electric motor is operatively connected to one of the wheels;

a battery pack operatively connectable to power the electric motors;

a speed sensor positioned at each wheel to determine the speed thereof; a controller configured to receive signals from the speed sensors, wherein, during acceleration, the controller is programmed to determine if each of the wheels is incurring wheelspin and to control an accelerative torque to each electric motor independently to inhibit wheelspin at each wheel.