HYBRID VEHICLE

The present invention relates to a hybrid vehicle, that is a vehicle which can be driven by an internal combustion engine, by electric motors (or hydraulic motors) and by a combination of internal combustion engine and electric motors (or hydraulic motors) .

Hybrid vehicles are now well known. In known hybrid vehicles an electric traction motor is located on the engine side of the differential which splits drive between the wheels on opposite sides of a vehicle. The internal combustion engine and the electric traction motor both drive the driven wheels via the differential.

The present invention in a first aspect provides a hybrid vehicle comprising: a heat engine; an electrical generator driven by the heat engine; a transmission which can connect the heat engine to the pair of driven wheels via a differential; and a plurality of electric motors, each electrical motor being associated with a respective wheel of the driven wheels and located wheel-side of the differential; wherein the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the electrical motors associated with the driven wheels and the heat engine is either inactive or drives the electrical generator; and a second operating mode in which the vehicle is driven both by the electrical motors associated with the driven

wheels and by the heat engine driving the driven wheels through the transmission and via the differential.

The present invention in a second aspect provides a hybrid engine comprising: a heat engine; an electrical generator driven by the heat engine; at least two pairs of driven wheels; a transmission which can connect the heat engine to a first pair of the driven wheels; and a plurality of electrical motors, each electrical motor being associated with a respective wheel of a second pair of the driven wheels; wherein: the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the electrical motors associated with the second pair of driven wheels and the heat engine is either inactive or drives the electrical generator; and a second operating mode in which the vehicle is driven both by the electrical motors associated with the second pair of driven wheels and by the heat engine driving the first pair of driven wheels through the transmission and via the differential.

The present invention provides in a third aspect a hybrid vehicle comprising: a heat engine; an electrical generator driven by the heat engine; at least two pairs of driven wheels; a transmission which can connect the heat engine to a first pair of the driven wheels via a differential; and

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a plurality of electrical motors, one electrical motor being provided and associated with each of the driven wheels of the two pairs of driven wheels, the electrical motors associated with the driven wheels of the first pair being located wheel-side of the differential; wherein: the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the electrical motors associated with the driven wheels and the heat engine is either in active or drives the electrical generator; and a second operating mode in which the vehicle is driven both by the electrical motors associated with the driven wheels and by the heat engine driving the fist pair of driven wheels through the transmission and via the differential.

The present invention in a fourth aspect provides a hybrid vehicle comprising: a heat engine; a hydraulic fluid pump driven by the heat engine; at least one pair of driven wheels; a transmission which can connect the heat engine to the pair of driven wheels via a differential; and a plurality of hydraulic motors, each hydraulic motor being associated with a respective wheel of the pair of driven wheels and located wheel-side of the differential; wherein: the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the hydraulic motors associated with the driven wheels and the heat engine drives the hydraulic fluid pump; and

a second operating mode in which the vehicle is driven both by the hydraulic motors associated with the driven wheels and by the heat engine driving the driven wheels through the transmission and via the differential.

The present invention in a fifth aspect provides a hybrid vehicle comprising: a heat engine; a hydraulic fluid pump driven by the heat engine; at least two pairs of driven wheels; a transmission which can connect the heat engine to a first pair of the driven wheels; and a plurality of hydraulic motors, each hydraulic motor being associated with a respective wheel of a second pair of the driven wheels; wherein: the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the hydraulic motors associated with the second pair of driven wheels and the heat engine drives the hydraulic fluid pump; and a second operating mode in which the vehicle is driven both by the hydraulic motors associated with the second pair of driven wheels and by the heat engine driving the first pair of driven wheels through the transmission and via the differential.

The present invention in a sixth aspect provides a hybrid vehicle comprising: a heat engine; a hydraulic fluid pump driven by the heat engine; at least two pairs of driven wheels;

a transmission which can connect the heat engine to a first pair of the driven wheels, via a differential; and a plurality of hydraulic motors, one hydraulic motor being provided for and associated with each of the driven wheels of the two pairs of driven wheels, the hydraulic motors associated with the first pair of driven wheels being located wheel-side of the differential; wherein: the hybrid vehicle has: a first operating mode in which the vehicle is driven solely by the hydraulic motors associated with the driven wheels and the heat engine drives the pump; and a second operating mode in which the vehicle is driven both by the hydraulic motors associated with the driven wheels and by the heat engine driving its first pair of driven wheels through the transmission and via the differential .

The present invention provides in a seventh aspect a hybrid motorcycle comprising: an internal combustion engine; an electrical generator driven by the internal combustion engine; a transmission which can connect the internal combustion engine to a rear wheel of the motorcycle; and at least one electric motor associated with at least one wheel of the motorcycle; wherein: the hybrid motorcycle has : a first operating mode in which the motorcycle is driven solely by the electric motor (s) associated with the wheel (s) of the motorcycle and the internal combustion engine is decoupled from the rear wheel by the transmission; and

a second operating mode in which the motorcycle is driven both by the electrical motor (s) associated with the wheel (s) of the motorcycle and by the internal combustion engine driving the rear wheel through the transmission.

The present invention provides in an eighth aspect a hybrid motorised tricycle comprising: an internal combustion engine; an electrical generator driven by the internal combustion engine; a transmission wheel which can connect the internal combustion engine to a first of a pair of rear wheels of the tricycle; at least one electric motor associated with at least one wheel of the tricycle; wherein: the tricycle has: a first operating mode in which the tricycle is driven solely by the electric motor (s) associated with the wheel (s) of the tricycle and the internal combustion engine is decoupled from the first rear wheel by the transmission; a second operating mode in which the tricycle is driven both by the electrical motor (s) associated with the wheel (s) of the motorcycle and by the internal combustion engine driving the first rear wheel through the transmission.

The present invention provides in a ninth aspect a hybrid motorcycle comprising: an internal combustion engine; a hydraulic pump driven by the internal combustion engine; a transmission which can connect the internal combustion engine to a rear wheel of the motorcycle; and

at least one hydraulic motor associated with at least one wheel of the motorcycle; wherein: the hybrid motorcycle has: a first operating mode in which the motorcycle is driven solely by the hydraulic motor (s) associated with the wheel (s) of the motorcycle and the internal combustion engine is decoupled from the rear wheel by the transmission, and a second operating mode in which the motorcycle is driven both by the hydraulic motor (s) associated with the wheel (s) of the motorcycle and by the internal combustion engine driving the rear wheel through the transmission.

The present invention provides in a tenth aspect a hybrid motorised tricycle comprising: an internal combustion engine; a hydraulic pump driven by the internal combustion engine; a transmission which can connect the internal combustion engine to a first of a pair of rear wheels of the tricycle; and at least one hydraulic motor associated with at least one wheel of the tricycle; wherein: the tricycle has: a first operating mode in which the tricycle is driven solely by the hydraulic motor (s) associated with the wheel (s) of the tricycle and the internal combustion engine is decoupled from the first rear wheel by the transmission; a second operating mode in which the tricycle is driven by both the hydraulic motor (s) associated with the wheel (s) of the motorcycle and by the internal combustion engine driving the first rear wheel through the transmission.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic layout drawing of a first embodiment of a hybrid drive system according to the present invention for a rear wheel drive hybrid vehicle operating in a first operating mode;

Figure 2 is a schematic layout drawing of the Figure 1 hybrid drive system operating in a second operating mode; Figure 3 is a schematic layout drawing of a second embodiment of a hybrid drive system according to the present invention for a rear wheel drive hybrid vehicle;

Figure 4 is a schematic layout drawing of a third embodiment of a hybrid drive system according to the present invention, for a transverse/front wheel drive hybrid vehicle; and

Figure 5 is a schematic layout drawing of a fourth embodiment of a hybrid drive system according to the present invention.

In Figure 1 there can be seen a schematic drawing of the layout of a hybrid drive system for a hybrid vehicle. The drive system 10 comprises an internal combustion engine 11, a generator 12 (which also functions as an electric starter) , a reduction gear set 13, a differential 18 and hub motors 14 and 15 associated respectively with wheels 19 and 20. The differential 18 acts between the driven wheels 19 and 20. In Figure 1 the hybrid drive system is working in series operation. The engine 11 is used to drive an electrical generator 12 which then generates electrical power supplied to a battery (not shown) and also to the electric hub motors 14 and 15. The driven wheels 19 and 20

are driven electrically by the electric hub motors 14 and 15. The engine 11 is disconnected from the wheels 19 and 20 by the gear set 13. This is shown by a gear 16 mounted on a shaft 21 connected to the engine 11 being shown out of mesh with a gear 17 mounted on a shaft 22 connected to the differential 18.

Figure 2 shows the hybrid drive system of Figure 1 in a second mode of operation, a parallel mode of operation. In this mode of operation the engine 11 is connected via the gear set 13 and differential 18 to the driven wheels 19 and 20 to drive the wheels 19 and 20. The engine 11 drives the wheels 19 and 20 in parallel with the electric hub motors 14 and 15. The engine 11 may in this mode also drive the generator 12 to produce electric power for the hub motors 14 and 15 or in this mode the hub motors 14 and 15 may draw power only from the battery (not shown) with operation of the generator 12 suspended so that the generator 12 does not draw power from the engine 11. In the Figure 2 it can be seen that the gear 12 mounted on shaft 21 is in mesh with the gear 17 mounted on gear 22.

Where the hybrid drive system illustrated in Figures 1 and 2 differs from those known in the prior art is in the use of hub motors as traction motors driving the driven wheels instead of a dedicated traction motor which drive the driven wheels via a differential. The hub motors 14 and 15 will be used for full regenerative braking; i.e. the hub motors 14 and 15 will be used to brake the driven wheels 19 and 20 and in the process generate electric power to be relayed to the battery (not shown) . The battery could be supplemented as a storage device by a capacitor or a

flywheel - in fact the type of accumulator is not important to the invention.

The hub motors 14 and 15 will be designed to make them capable of full regenerative braking i.e. there is no need for additional brakes. This does lead to a trade off in the motors' abilities to drive the driven wheels 19 and 20 at high speed. This is overcome by the high speed parallel mode of Figure 2 in which the engine 11 will supply most of the tractive effort. In the Figure 2 parallel mode of operation the hub motors 14 and 15 will merely be used to boost the performance of the engine 11 or to increase loading on the engine 11 to improve the efficiency of operation of the engine 11 whilst recharging the battery (not shown) ; in other words, in the parallel mode the motors 14 and 15 can be used as generators in addition to generator 12 to generate power relayed to a battery for storage .

At low speeds the hybrid drive system of Figures 1 and 2 uses the hub motors 14 and 15 as traction motors with the engine 11 used to provide electrical energy only (i.e. the Figure 1 operating condition) . In this condition there is no mechanical link between the engine 11 and the driven wheels 19 and 20. This means that the generator 12 can be designed to function very efficiently since it does not have to act as a traction motor at all (in the prior art systems the electric traction motor would also have doubled as generator) . The only tractive power to be supplied by the generator 12 is power to act as a starter for the engine 11. Even this requirement could be dispensed with by the use of

an additional starter so that the generator 12 functions only as a generator.

The switchover from the Figure 1 operation to the Figure 2 operation would happen by first starting the engine 11 (if it were not previously running) and then synchronising the speed of the engine crankshaft 21 with the differential shaft 22 so that the gears 16 and 17 can be engaged without the need for a clutch. This also means that only one gear set 13 is required, the gears 16 and 17 of which can be dogged into engagement (thereby saving the cost of synchromesh and reducing mass and complexity) . However, more gear sets could be used if desired.

Ideally, no foundation brakes would be used in the vehicle at all for the driven wheels 19 and 20 and instead all braking would be provided by the hub motors 14 and 15. However, foundation brakes could be provided to provide a fail-safe arrangement or to act in parallel if so required by law.

The hybrid system described above allows better optimisation of the electrical components by use of two modes of operation.

The internal combustion engine 11 could be of a number of different types. For instance, the engine 11 could be a 4-stroke engine with two different modes of operation; for the series mode of operation (figure 1) the engine 11 could be operated in an HCCI (homogeneous charge compression ignition) operating mode, whilst the engine 11 could be operated in conventional gasoline spark (Otto cycle)

ignition or in compression ignition (diesel) operating mode for the parallel operation of the system shown in Figure 2. Alternatively, a two-stroke engine could be used as the engine 11, the engine operating with a wide range of HCCI combustion; the hybrid drive system could eliminate idle operation and low speed operation of the engine 11 and thus possibly make the use of a two-stroke HCCI engine the ideal choice. Additionally, a Wankel engine could be used as the engine 11; Wankel engines do not operate efficiently at low speeds and loads but have a much higher degree of efficiency (comparable to a 4-stroke engine) at high loads, with the advantages of compactness and low vibration when compared to a reciprocating piston engine. Additionally, the arrangement of Figures 1 and 2 does not require the internal combustion engine 11 to run at all times (indeed the engine 11 would be inactive at low speed operations) - this would extend the durability of a Wankel engine, which would last significantly longer when the engine operation is considered in terms of distance travelled by a vehicle.

Whilst above the system 10 is described as avoiding the need for a clutch by synchronisation of the shaft speeds of shafts 21 and 22 prior to engagement of gears 16 and 17, an alternative approach would be to use a clutch 31 in a system 30 as shown in Figure 3. The components of the system 30 which correspond with the components of the system 10 of Figures 1 and 2 have been given reference numerals identical to those of Figures 1 and 2. Once more the driven wheels 19 and 20 are each provided with a hub motor 14 and 15 and an internal combustion engine 11 can additionally drive the driven wheels 19 and 20 via a differential 18. Once more a generator 12 can be driven by the engine 11 to generate

electrical power. In the Figure 3 embodiment the gears 16 and 17 are in constant mesh. The clutch 31 is provided to switch the hybrid system between series operation and parallel operation. When the clutch 31 disconnects engine 11 from the gear 16 then the engine 11 will operate in series operation in the same way as shown in Figure 1 and will operate to drive the generator 12 to generate electrical power (or alternatively will remain inactive) . When the engine 11 is connected via clutch 31 to the gear 16 then the engine 11 will provide traction power to the driven wheels 19 and 20 in addition to any tractive power supplied by the hub motors 14 and 15.

Instead of using a clutch as shown in Figure 3, it is possible to replace the meshed gears 16 and 17 with an epicyclic gear arrangement and then control by braking the rotation of the planet cage and/or the annulus to either allow transmission of motive power from the engine 11 via differential 18 to the driven wheels 19 and 20 or to allow the engine 11 to rotate independently of the rotation of the driven wheels 19 and 20.

The arrangements of Figures 1 to 3 illustrate the driving of a pair of rear wheels of a vehicle, but the invention is equally applicable to the driving of front wheels of a vehicle. In Figure 4 there is a hybrid drive system layout 40 shown which is for a transverse engine and front wheel drive application. The components of the system 40 which are components in common with the previous systems described have been given the same reference numerals. The Figure 4 system 40 is, in many ways, identical to the system of Figures 1 and 2, save that the orientation of the engine

11 is transversely across the vehicle rather than longitudinally along it and the shafts 21 and 22 extend transversely across the vehicle rather than longitudinally along the vehicle. The hybrid drive system will operate with a series operation and parallel operation in the same way as previously described for Figures 1 and 2.

Although the possibility is not illustrated in drawings attached, the present invention could also be applied to a 4-wheel drive vehicle. In a 4-wheel drive application there could be a hub motor associated with each of the 4 wheels of a vehicle, in order to maximise regenerative braking potential. The mechanical drive for the engine could be transmitted to all 4 wheels of such a vehicle, or to only 2 wheels. It is also possible to arrange a 4-wheels drive application with a mechanical drive to 2 wheels and the electrical drive via hub motors to the other 2 wheels.

The present invention could be applied to mid-engined and rear-engined vehicles as well as front-engined vehicles as described above.

The present invention also envisages a system in which the internal combustion engine 11 of the previous embodiment is replaced with a gas turbine; this is illustrated in

Figure 5. In Figure 5 a hybrid drive system 50 is shown in which a free power gas turbine 51 is coupled to electrical generator 52 which also acts as a starter for the gas turbine 51. The gas turbine 51 will drive an output shaft connected to the generator 52 to cause the generator 52 to generate electrical power. The gas turbine 51 will also have an output of pressurised gases. These will be relayed

to a free power turbine 53 to drive the turbine 53 to rotate. The turbine 53 is then connected via a shaft 54, a gear 55, a gear 56 and a shaft 57 to a differential 58 and through the differential 58 to a pair of driven wheels 59 and 60. Electric hub motors 61 and 62 are respectively- associated with the driven wheels 59 and 60. The hub motors 61 and 62 will be powered by electricity generated by the gas turbine 51 and/or stored in a battery (not shown) . The battery will be charged by electricity generated by the generator 52.

With the arrangement shown in Figure 5, control of how much mechanical power is delivered via the differential 58 to the driven wheels 61 and 60 can be achieved by control of the operation of the generator 52. By reducing the work extracted from the driven shaft by the generator 52 the power produced by the free power turbine 53 is increased. Therefore, there is a gradual switching process with the low speed operation involving maximising electrical power generated by the generator 52 and the high speed operation minimising electrical power generated by generator 52 so that the mechanical power provided by turbine 53 is maximised. There will be smooth transition between these two extremes with varying vehicle speed.

The hub motors of all of the embodiments described above could additionally be used to provide traction control and stability control for the vehicle and also anti-lock braking. Rather than being mounted on the wheels themselves, as illustrated, the hub motors could be attached to the lay shafts extending between the differential and the driven wheels.

Whilst above the hub motors are described as electric motors and indeed this is preferred, it is possible that the hub motors could be hydraulic motors instead, with the electrical generator replaced by a pump generating a supply of pressurised hydraulic fluid. The electrical accumulator (e.g. battery) would be replaced by a hydraulic accumulator; a flywheel could be used as well to store energy.

The present invention could also be applied to motorcycles and tricycles. In a motorcycle, a hub motor would be provided for the rear wheel and the heat engine selectively coupled to the rear wheel to drive the rear wheel alone or in co-operation with the hub motor or selectively decoupled from the rear wheel so that the rear wheel is driven by the hub motor alone. Alternatively, the hub motor could be used to drive the front wheel and the heat engine used selectively to drive the rear wheel.

In the case of a motorised tricycle, the pair of rear wheels could be each provided with a hub motor and the heat engine selectively used to drive the rear wheels via a differential provided for the rear wheels. However, in some cases a tricycle will have only one wheel driven by the heat engine. Then in an arrangement according to the present invention the heat engine will be selectively coupled to only one rear wheel and either: a hub motor provided for each rear wheel; a hub motor provided for all three wheels; or a hub motor provided for only the rear wheel which would be driven by the heat engine.