HUBS FOR ELECTRIC HYBRID VEHICLES

The present invention refers to hubs, particularly vehicle hubs, and is particularly concerned with hubs for electric hybrid vehicles.

Electric hybrid vehicles have a mechanical source of power, such as a conventional internal combustion engine, and an electrical source of power, typically an electric motor powered by a battery and/or a generator driven by the engine. The power produced by these two sources must be combined in some mechanical device and then fed to the driven wheel or wheels of the vehicle. Such a vehicle conventionally includes all the normal automotive components such as a clutch, differential and gear box, in addition to the bulky power combining device which not only adds to the weight of the vehicle but also takes up valuable space.

The space within the hubs of a vehicle is generally largely empty and it would be highly desirable if this space could be used to accommodate the power combining device of a hybrid vehicle or a purely electrically driven vehicle. However, the wheels of a vehicle are of course unsprung because they are connected to the body of the vehicle via the vehicle suspension system and it is very undesirable to increase the unsprung weight of a vehicle because this severely impairs the road handling characteristics and driveability of the vehicle.

According to the present invention, there is provided a hub comprising a generally cylindrical hollow hub member, which is mounted to rotate about its axis and at least partially accommodated in whose interior is a transmission system having an input, which is mounted to rotate about the axis, and an output connected to rotate with the hub member, the transmission system

including a three branch differential gearset comprising a sun gear connected to rotate with the input, one or more planet gears which are rotatably carried by a common carrier and are in mesh with the sun gear, and a ring gear in mesh with the planet gears, the transmission system further including a single first reversible machine including a rotor connected to rotate with one of the carrier and the ring gear, the other of which is connected to rotate with the hub member.

In use, the input will be connected to a source of mechanical power and the stator connections of the reversible machine will be connected to a source or an absorber of power via a controller arranged to control the flow of power. The reversible machine maybe a hydrostatic motor/pump and in this event it is referred that the source/absorber of power is a further hydrostatic motor/pump. It is, however, preferred that the reversible machine is an electric motor/generator and that the source/absorber of power is a further motor/generator. The controller will be selectively controlled to determine the magnitude of the power flow and whether this power flow is to or from the reversible machine in the hub. Altering the speed of the reversible machine in the hub will alter the effective transmission ratio between the input and output of the transmission system and will thus allow the speed of the hub to be varied independently of the speed of the mechanical input. The power supplied to or taken from the reversible machine in the hub will be added to or subtracted from the mechanical supplied to input and this independent control of both output speed and power means that the torque output at the hub member may be controlled independently of the output speed.

If the first reversible machine is a motor/generator, it is preferably arranged to operate at high speed and this will allow it to be relatively small and light. The operating speed may well be too high for the motor/generator to be coupled

directly to the differential gearset and it is therefore preferred that step-down gearing, preferably of epicyclic type, is interposed between it and the gearset.

Whilst the hub of the present invention may have many applications, it is primarily intended for use in a driven wheel of a motor vehicle. Thus the invention also embraces a motor vehicle including a motor with an output shaft and at least one driven wheel including a hub of the type referred to above, the output shaft of the motor being connected to the input of the differential gearset, the vehicle further including a second reversible machine, the stator connections of which are connected to the stator connections of the first reversible machine via a controller arranged to control the flow of power between the two machines.

The motor may be an internal combustion engine of any sort but the vehicle may also be a wholly electrical vehicle powered by e.g. a battery and in this case the motor will be an electric motor. Whilst a dedicated electric motor may be provided for this purpose it is preferred that the motor is constituted by the second reversible machine, which in this case will be an electric motor/generator. In this event, the onboard motor/generator will of course operate for the majority of the time as a motor.

The fact that the hub may be controlled as regards output speed and torque and that the transmission system of the hub inherently provides a "geared neutral" that is a condition in which the input is rotated but no torque is applied to the output, that is to say to the wheel of which the hub forms part, means that the conventional clutch and gear box may be omitted thereby saving a substantial amount of expense and weight. The motor vehicle may be a motor cycle or a three- wheeled vehicle with only one driven wheel, but if it has two or more driven wheels the conventional differential, which splits power between the

wheels on an axle or between two axles may also be omitted since its function may also be played by the fully controllable transmission systems of the hubs. Although the vehicle may have two or four or even more hubs and thus a corresponding number of first reversible machines, only a single second reversible machine is required.

The addition of a transmission system and a reversible machine to the hub will of course tend to increase its weight and thus to increase the unsprung mass of the vehicle. However, if the reversible machine is a motor/generator, it may be used as a regenerative brake and fulfil the function of a conventional brake under at least moderate braking conditions. The electrical power generated will be directed by the controller to the battery, which is in any event always provided on motor vehicles for starting, lighting and ignition purposes. The motor/generator can not, as a practical matter, supply the braking power required during an emergency stop but it has been appreciated that it is not necessary to provide each hub of the vehicle with a respective brake for this purpose and that it is perfectly adequate if the vehicle includes a single brake acting on the output shaft of the motor or the connection between it and the input to the or each transmission system. Thus in this embodiment, the hubs include no brake and the removal of the conventional brake and the accompanying weight reduction compensate for the weight of the transmission system and the motor/generator, whereby the hub in accordance with the invention will weigh substantially no more than a conventional vehicle hub with an associated braking system. There is therefore substantially no increase in the unsprung weight of the vehicle but there is a substantial decrease in the overall weight of the vehicle due to the ability to eliminate the conventional clutch, gear box and differential. Furthermore, there is no need for the output speed of the motor to be stepped-down before being transmitted to the hubs which will mean that the transmission shaft or shafts of the vehicle will in

practice rotate faster than is usual, whereby the gears associated with them may be smaller and lighter than usual, thereby resulting in a further financial economy and saving in weight.

Further features and details of the invention will be apparent from the following description of certain specific embodiments which is given by way of example with reference to the accompanying diagrammatic drawings, in which: FIG 1 is an axial sectional view of a hub in accordance with the invention;

FIG 2 is a similar view of a modified construction of hub;

FIG 3 is a highly schematic view of the driven axle of a motor vehicle in accordance with the invention;

FIG 4 is a view similar to FIG 3 of a modified embodiment of a motor vehicle in accordance with the invention;

FIG 5 is a view similar to FIG 4 showing a four-wheel drive vehicle in accordance with the invention; and

FIG 6 is a further similar view of a motor cycle in accordance with the invention.

The hub illustrated in FIG 1 is a steered hub suitable, for instance, for use on a front wheel drive passenger vehicle. The hub comprises an input shaft 4, which is supported by a hub support 76, which is shown only schematically. In use, the input shaft 4 will be connected to a driveshaft 106 via a constant velocity joint 108. Extending around a portion of the input shaft 4 is a hub

member 2, which is of hollow, generally cylindrical shape and is mounted to rotate with respect to the hub support 76 by means of bearings 6 and sealed by means of an oil seal 78. Attached to the end of the input shaft 4 remote from the driveshaft 106 is a sun gear 16 which rotates with the input shaft 4. The sun gear 16 is in mesh with a number, typically 3 or more, of planet gears 20 which are mounted to rotate about respective planet shafts 22. The planet shafts 22 are connected as is usual, to a common carrier and this is constituted in the present case by a portion of the hub member 2. The planet gears 20 are in mesh with an annulus or ring gear 36. The ring gear 36 is connected to an annular support plate 26 and these two components are mounted to rotate about the axis of the input shaft 4 via a bearing 19. The ring gear 36 is in mesh not only with the planet gears 20 but also with further planet gears 30, which are mounted on respective further planet shafts 32. The planet shafts 32 are carried by a stationary carrier 66. The planet gears 30 are in mesh with a further sun gear 56, which is mounted to rotate about the axis of the shaft 4 means of a bearing 12. The sun gear 56 is connected to a gear wheel 54 in mesh with a further gear wheel 46 connected to the input/output shaft of a reversible machine 42, which is controlled by means of circuitry indicated schematically at 48. In this case, the reversible machine 44 is a hydrostatic motor/pump but it could also be an electric motor/generator. The reversible machine 44 is constructed to rotate very rapidly, so that its size may be kept relatively small, and the gear wheels 56, 30, 36 constitute the step-down gearing.

In use, the hub will carry a tyre and the input shaft 4 will be connected to the output of a motor, typically a conventional internal combustion engine. The input and output connections of the stator of the hydraulic motor/pump will be connected to the output/input reports of a further reversible hydraulic motor/pump situated on the vehicle. A controller will vary the flow rate and direction of flow of pressurised hydraulic fluid between the two reversible

machines. The precise manner in which the hub operates and is controlled will be described below.

The modified hub shown in FIG 2 is very similar to that of FIG 1. However, whilst the hub in FIG 1 has an offset reversible machine 44, in order to facilitate the use of a hydraulic motor/pump, the hub of FIG 2 uses an electric motor/generator within the hub 2. Thus the reversible machine includes a rotor 24 carrying magnetic materials 70 which co-operates with a static winding 42 carried by a stator 66. The rotor 24 is again connected to the input differential 16, 20, 26 via step-down gearing in the manner described in relation to FIG 1. A few other minor instructural modifications have also been made such as the fact that the planet shafts 32 of the step-down planet gears 30 are carried by a static support plate 14. The plate 26 is mounted to rotate about the axis via a bearing 19. Connected to the plate 26 is a separate ring gear 36.

FIG 3 is a schematic representation of the two driven wheels of a front wheel drive vehicle in accordance with the invention incorporating a two cylinder opposed piston engine 112. The two wheels 104 include steered hubs of the type illustrated in FIG 2, which are connected via constant velocity joints 108 to respective drive shafts 106, which are connected via further respective constant velocity joints 108 to the crankshaft 114 of the engine. Also connected to the crankshaft of the engine is the rotor 28 of a further motor/generator which carries magnetic material 70 and co-operates with a stator 40. The stator connections of the motor/generator 28, 40 are connected to a controller 50, which is connected in turn both to an energy store 52, in this case a rechargeable battery, and to the stator connections of the motor/generators of the two steerable hubs 102. The controller 50 is responsive to one or more sensors, particularly a sensor indicative of the position of the throttle or of the accelerator pedal of the engine, and controls

the magnitude of the power supplied to or taken from the two motor/generators of the hubs to produce the desired output speed and torque at each of the hub members 2. The rotor 28 of the motor/generator 28, 40 is connected to rotate with one of the drive shafts 106. One of the drive shafts 106 carries a brake disc 118 which co-operates with a brake calliper 116 operable to brake the drive shafts. The provision of this brake assembly means that the brake mechanism conventially provided in vehicle hubs may be omitted, thereby reducing their overall weight. In use, either the motor/generators in the hubs or the motor/generator mounted on the vehicle body acts as a generator and transmits electrical power to the other, which acts as a motor. The amount of electrical power so transmitted may be selectively varied by means of the controller thereby altering the transmission ratio of the transmission system. Power is transmitted through the transmission system both mechanically and electrically in proportions which vary with the varying transmission ratio. The output speeds of the transmission system and thus the speeds of the hub members may thus be varied independently of the input speed, which means that the speed of the wheels of which the hubs in accordance with the invention form part may be varied independently the speed of the engine, which means in turn that each wheel may be operated precisely at the speed and torque which is the most appropriate for the driving conditions of the vehicle.

The electric motor/generators are thus not only the means by which the transmission ratio of the hub transmission systems may be continuously varied but also the means by which electrical power from the vehicle battery 52 may be converted into mechanical power and transmitted to the driven wheels. The onboard motor/generator can also serve a further function in that it may fulfil the function not only of the conventional alternator, which is used to produce electric power to recharge the battery, but also the function of the conventional starter motor. A vehicle including a wheel with a hub in accordance with the

present invention therefore need not be provided with the usual alternator and starter motor. As mentioned previously, the conventional clutch and differential may also be omitted as well. If it is desired to brake the vehicle moderately, the controller is operated to direct substantial amounts of power from the motor/generators in the hubs to the battery to recharge it, thereby braking the driven wheels. If hard braking or emergency braking is required, the hub motor/generators are unable to apply sufficient braking force and in this event the brake 116, 118 is also applied.

FIG 4 is a view similar to FIG 3 of a slightly modified embodiment. In this case, the engine 120 is of more conventional type and its crankshaft 114 is connected to the two transmission shafts 106 by a transfer gear box 122. The crankshaft is also connected to the rotor 28 of the motor/generator 28, 40. The crankshaft is also connected to a brake disc 118 co-operating with a brake calliper 116, though the brake assembly 116, 118 may again be associated with the drive shafts 106, e.g. in the position indicated in FIG 4 by the chain dotted box 117. In other respects, this embodiment is the same and operates in the same manner as that of FIG 3.

The embodiment of FIG 5 is similar to that of FIG 4 but in this case the vehicle is of four wheel drive type. In this case, the two front hubs 102 are of steerable type as previously, but the two rear hubs 100 are of non-steerable type. One of the front transmission shafts includes a bevel gearbox 124 with an output shaft 128 extending rearwardly. Drive transmitted to the transmission shaft 128 is transmitted to the rear drive shaft through a further bevel gearbox 126. The brake assembly 116 is again connected to the crankshaft of the engine but could be positioned, for instance, at either of the positions indicated by the chain line boxes 117. The speed and torque of all four hubs are controlled independently by the controller 50 and there is thus again no need for a

differential on either the front or rear axle or indeed a differential splitting power between the front and rear axle.

Finally, FIG 6 is a further highly schematic view of a motor cycle with a rear driven wheel 104 incorporating a non-steered hub 98, the input shaft of which carries a bevel gear 8. The motor cycle has a 2 cylinder opposed piston engine 112, the crankshaft 114 of which is connected to the rotor 28 of a motor/generator 28, 40. The crankshaft, or a shaft connected directly to it, also carries a brake disc 118 co-operating with a brake calliper 116 and is connected to a transfer box 122, the output of which is connected via a constant velocity joint 108 to a drive shaft 106, which is connected to bevel gear box 128 including the input bevel gear 8. The construction and operation of this embodiment is otherwise much as in the previous embodiments, though the controller 50 is of course simpler because there is only a single hub to be controlled.