WO2015107368A1

WO2015107368A1 - A power unit and a vehicle

Info

Publication number: WO2015107368A1
Application number: PCT/GB2015/050112
Authority: WO
Inventors: David Wykes
Original assignee: Mira Limited
Priority date: 2014-01-20
Filing date: 2015-01-19
Publication date: 2015-07-23
Also published as: GB201400945D0; GB2522261A; GB2522261B

Abstract

A power unit for a vehicle, the power unit comprising: a motor configured to drive rotation of a first driveshaft; a motor-generator configured to drive rotation of a motor-generator driveshaft; and an accessory or ancillary configured to be driven by the motor-generator driveshaft, wherein the first driveshaft and motor-generator driveshaft are selectively engageable such that rotation of the motor-generator driveshaft is driveable by the first driveshaft.

Description

Title: A power unit and a vehicle Description of Invention

The invention relates to a power unit, and a vehicle incorporating a power unit. Embodiments of the invention relate to an auxiliary power unit for powering one or more ancillaries or accessories.

Modern vehicles often include a number of ancillaries and accessories. The term 'ancillaries' is often used to describe devices which are required for (or which are complementary to) the operation of a prime mover (such as an internal combustion engine) of the vehicle, while the term 'accessory' is normally used for referring to other devices which have another useful purpose in relation to the vehicle's function. For avoidance of doubt, the terms 'ancillary' and 'accessory' are used interchangeably, herein.

Many road vehicles have one propulsive motor, which is used to propel the vehicle and also to power ancillaries and accessories of the vehicle. The power to the ancillaries and accessories is either transferred mechanically in the form of rotational motion, or in an alternative manner (such as via a hydraulic or pneumatic system, or by transferring energy to a battery of the vehicle which can provide electrical power to the ancillaries and accessories). Typically, the propulsive motor is an internal combustion engine.

In electric vehicles, electric motor(s) are the source of propulsive force for the vehicle, and these are powered by batteries of the vehicle. In vehicles equipped only with electric motors, users typically complain of having a relatively low range of travel compared to an engine with an internal combustion engine, and this can present an issue due to the batteries taking a comparatively long time to recharge. In order to address this problem, an auxiliary power unit (APU) may be provided in an electric vehicle.

APUs are used to provide power independently of the main propulsive motor(s) of the vehicle. Electric vehicles equipped with an APU are typically called a 'range-extender' hybrid. Such vehicles use electric motors to provide propulsive force for the vehicle, but use an APU (typically including an internal combustion engine) to recharge the batteries of the vehicle when necessary. The APU drives a generator and the electric power from the generator is used to drive electric motors of the vehicle and/or is stored in batteries for later use.

Such arrangements have the advantage that a fuel tank of the APU can be filled relatively quickly, and the APU can then be used to charge the batteries of the vehicle while the vehicle is moving. This increases the range of the vehicle.

As the APU is not driving movement of the vehicle directly, unlike a conventional internal combustion engine vehicle, the APU can be run at its most efficient operating condition (e.g. speed) to recharge the batteries. This allows for favourable fuel use and emission release.

In vehicles in which internal combustion engines provide the propulsive force for the vehicle, APUs may be provided in order to power the ancillaries and accessories, such that the ancillaries and accessories are powered separately from the propulsive motor of the vehicle.

Typically, there are two approaches to powering the accessories and ancillaries of vehicles with APUs. In some arrangements the accessories and ancillaries are linked to the internal combustion engine of the APU to transfer power mechanically, and in other arrangements they are electrically powered using power stored in batteries of the vehicle (which may have been generated by one or more electrical generators coupled to the internal combustion engine of the APU). However, both of these arrangements have disadvantages. Powering the ancillaries through a mechanical power transfer from the internal combustion engine of the APU means that the ancillaries and accessories can only be used when the internal combustion engine is running. This means that, when the internal combustion engine of the APU is not operating (e.g. because the vehicle batteries are not being charged in a hybrid vehicle), the user must either do without several of the accessories, or must start the internal combustion engine of the APU. It may not always be convenient to start the internal combustion engine of the APU - for example, in busy urban or residential areas where the air pollution and noise caused by an internal combustion engine may cause irritation, or in the case of a military vehicle where it may be necessary to minimise noise (or the generation of heat) to avoid detection.

The alternative arrangement whereby ancillaries are powered electrically overcomes some of these disadvantages, as the ancillaries can be used when the internal combustion engine of the APU is not operating. However, such an arrangement also has disadvantages. For example, each ancillary typically includes its own electric motor and the number of electric motors required to power all of the ancillaries adds significantly to the weight, cost, complexity, and size of the arrangement.

Embodiments of the present invention, therefore, seek to ameliorate one or more problems associated with the prior art.

Accordingly, an aspect of the present invention provides a power unit for a vehicle, the power unit comprising: a motor configured to drive rotation of a first driveshaft; a motor-generator configured to drive rotation of a motor- generator driveshaft; and an accessory or ancillary configured to be driven by the motor-generator driveshaft, wherein the first driveshaft and motor- generator driveshaft are selectively engageable such that rotation of the motor-generator driveshaft is driveable by the first driveshaft.

The motor may be an internal combustion engine.

The motor-generator may be an electric motor. The motor-generator may be configured to generate electricity when the first driveshaft is engaged with the motor-generator driveshaft and rotation of the motor-generator driveshaft is driven by the motor.

The power unit may further comprise an energy storage device which is configured to deliver electric power to the generator-motor in a mode of operation and to receive electric power from the generator-motor in another mode of operation.

The power unit may further comprise a first clutch part coupled for rotation with the first driveshaft and a second clutch part coupled for rotation with the motor- generator driveshaft, wherein the first driveshaft and the motor-generator driveshaft maybe engageable by engagement of the first and second clutch parts. Rotation of the motor-generator driveshaft may be driveable by a combination of the both the motor and the motor-generator.

The accessory or ancillary may be coupled to the motor-generator driveshaft by a drive coupling which is configured to be coupled to one or more further accessories or ancillaries. The power unit may further comprise a control system which is configured to synchronise the speed of rotation of the first driveshaft and the motor- generator driveshaft before engagement of the first driveshaft and motor- generator driveshaft.

The motor-generator driveshaft may be a through shaft of the motor-generator.

The power unit may be an auxiliary power unit. The motor-generator may be configured to provide a propulsive force for a vehicle.

Another aspect of the present invention provides a vehicle including a power unit.

The vehicle may be a hybrid vehicle.

The vehicle may be a heavy goods vehicle. The vehicle may be an aircraft, a boat, or a ship.

Embodiments of the present invention are described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a vehicle incorporating aspects of embodiments of the invention;

Figure 2 shows a power unit which incorporates aspects of embodiments of the invention in a first condition; Figure 3 shows a power unit which incorporates aspects of embodiments of the invention in a second condition;

Figure 4 shows a power unit which incorporates aspects of embodiments of the invention in a first condition in a first mode of operation;

Figure 5 shows a power unit which incorporates aspects of embodiments of the invention in a first condition in a second mode of operation; Figure 6 shows a power unit which incorporates aspects of embodiments of the invention in a second condition in a third mode of operation;

Figure 7 shows a power unit which incorporates aspects of embodiments of the invention in a second condition in a fourth mode of operation; and

Figure 8 shows a power unit with its control system according to embodiments of the invention.

The vehicle

With reference to Figure 1 , an embodiment of the present invention includes a vehicle 200. The vehicle 200 may comprise a heavy goods vehicle such as a lorry or truck, and may comprise a vehicle 200 equipped with accessories which are linked to its purpose. For example, the vehicle 200 may comprise a cement mixer, a crane, a fire engine, a dumper truck, a tipper, a gritting truck, a vehicle transporter, a forklift truck, a refrigerated truck, and may include a tail lift, a powered shovel, a compacting mechanism, a tank, an armoured personnel carrier, a self-propelled artillery vehicle, a mobile anti-aircraft vehicle, a mobile radar vehicle, a mobile missile vehicle, aircraft, boat, ship, or similar. The vehicle 200 may be an articulated or non-articulated vehicle 200. In some embodiments, the vehicle 200 is a refuse truck. The vehicle 200 may have a plurality of ground engaging wheels 202 which are mounted in pairs. One or more pairs of ground engaging wheels 202 may be driveable to move the vehicle 200 across a ground surface. As such, the one or more driveable ground engaging wheels 202 are mechanically coupled to a propulsive motor of the vehicle 200. The propulsive motor may be an internal combustion engine or may be an electric engine which includes one or more electric motors or may be a hybrid engine (which includes an internal combustion engine and one or more electric motors). The vehicle 200 may include an auxiliary power unit (APU) 100.

Motor

Referring now to figure 2, the APU 100 includes a motor 10, which in some embodiments may be an internal combustion engine.

The internal combustion engine may have an inlet manifold 12, an exhaust manifold 14, and a starter motor 16. The internal combustion engine is also coupled to a fuel tank which is configured to deliver fuel to the internal combustion engine and the internal combustion engine may include a carburettor or fuel injection system for mixing fuel supplied by the fuel tank with air for delivery to the inlet manifold - as will be appreciated.

The internal combustion engine may be configured to run on a fuel (stored in the fuel tank) such as gasoline, petroleum spirit, diesel fuel, ethanol, methanol, kerosene, liquefied petroleum gas, hydrogen, propane, butane, and/or biomass-derived fuels.

The internal combustion engine may be naturally aspirated or may be a forced induction engine. The internal combustion engine may have four cylinders 18, but any number of cylinders may be used, as required. Similarly, the cylinders may be in an inline configuration or any other suitable configuration. The internal combustion engine may be a two stroke engine, a four stroke engine, a radial engine, a rotary engine, a piston engine, a turbine engine, or any other suitable form of internal combustion engine.

The motor 10 (such as an internal combustion engine) may be oil cooled, air cooled or water cooled.

The motor 10 is configured to drive rotation of a first driveshaft 20.

In some embodiments, rotation of the first driveshaft 20 is not directly driven by the motor 10. Instead, the motor 10 may drive rotation of another driveshaft which is coupled to the first driveshaft 20 and configured to drive rotation thereof. The coupling may be via a gearbox and may be a selectively engageable coupling (e.g. through a clutch). In other embodiments, rotation of the first driveshaft 20 is directly driven by the motor 10.

In some embodiments, the first driveshaft 20 is coupled to, and configured to drive rotation of, a first clutch part 22.

The first clutch part 22 is configured to be selectively disengaged and engaged with another clutch part by a clutch actuation mechanism. In some embodiments, the clutch actuation mechanism is a hydraulic or pneumatic mechanism. In some embodiments, the clutch actuation mechanism is cable operated. The clutch actuation mechanism may be controlled by a control system 300 (and may include a hydraulic, pneumatic, or cable actuation system governed by a controller of the control system 300). In embodiments, the clutch actuation mechanism may include a linear or rotary actuator. The first clutch part 22 may be part of a friction clutch, an electromagnetic clutch, a clutch which uses clamping force, a dog clutch, or any other suitable arrangement.

In some embodiments, the first clutch part 22 may include, or be part of, a gearbox. That gearbox may be an epicyclic gearbox. In such embodiments, the epicyclic gearbox may be operable to engage or disengage, selectively, the coupling between the first driveshaft 20 and a part of the gearbox (such as a ring gear of the epicyclic gearbox) to transmit, or inhibit the transmission of, rotational motion from the gearbox (which is coupled to the motor 10) to the first driveshaft 20 selectively.

In some embodiments, the motor 10 is coupled to the control system 300. The control system 300 controls the operation of the motor 10 (such as the speed and/or direction of rotation of the first driveshaft 20) and may control the operation of other parts of the APU 100 (such as the clutch actuation mechanism). In some embodiments, the control system 300 may be configured to start the motor 10 on demand, and to run the motor 10 such that the first driveshaft 20 rotates at a predetermined speed (and in a predetermined direction). The control system 300 may, therefore, include a motor controller which is configured to start the motor 10 according to a set of predetermined instructions - a start-up routine. The motor controller may also be configured to start the motor 10 when one or more predetermined events occur, such as when the energy stored in an energy storage device 80 falls below a predetermined level, or in reaction to any other parameter, or combination of parameters. In some embodiments, the motor controller is configured to start the motor 10 on receipt of an instruction by an operator of the vehicle 200 (who may make the decision on when to start the motor 10 and/or at which speed it should be run). The vehicle 200 may, therefore, include gauges and/or displays to assist the operator with their decision and to provide an interface through which instructions from the operator can be passed to the motor controller (and/or other part of the control system 300).

It will be appreciated that motors, such as motor 10 (which may be an internal combustion engine), often vary in efficiency across different running speeds. In some embodiments, the control system 300 (e.g. through use of the motor controller) may be configured to operate the motor 10 to run at substantially its peak efficiency level. This peak efficiency level may be operation of the motor 10 at a predetermined speed, for example. In some embodiments, the operation of the motor is dependent on one or more sensed parameters which may include one or more environmental parameters which impact the efficiency of the motor 10 (e.g. atmospheric air pressure). Accordingly, the control system 300 may include one or more sensors. Motor Generator

The APU 100 includes a motor-generator 50. In some embodiments, the motor-generator 50 includes an electric motor. The motor-generator 50 may be mechanically coupled to a second driveshaft 52 and a third driveshaft 54.

The motor-generator 50 may be configured to drive rotation of second driveshaft 52 and the third driveshaft 54. In some embodiments, the second and third driveshafts 52,54 are mechanically coupled to each other such that rotation of one of the driveshafts 52,54 causes rotation of the other driveshaft 52,54.

In some embodiments, the second driveshaft 52 is configured for selective coupling with the third driveshaft 54 through a selective coupling mechanism (such as a clutch which may be a freewheel, or a centrifugal clutch). In some embodiments, the clutch is configured such that the second driveshaft 52 only engages the third driveshaft 54 when the second driveshaft 52 is rotating above a predetermined speed (and/or in a predetermined direction). In some embodiments, the operation of the clutch is controlled by the control system 300.

In some embodiments, the second driveshaft 52 and the third driveshaft 54 may be integrally formed as a single driveshaft. In such embodiments, it will be appreciated that references herein to the second driveshaft 52 apply to a first end of the single driveshaft, and references to the third driveshaft 54 apply to a second end of the single driveshaft. Accordingly, the second and third driveshafts 52 may be more generally referred to as the motor-generator 50 driveshaft 52,54 - which may be a single driveshaft or may comprise two or more coupled driveshafts (such as the second and third driveshafts 52,54).

The second driveshaft 52 may include a second clutch part 48, which is configured to be selectively engageable with the first clutch part 22 (under the control of the clutch actuation mechanism, in some embodiments).

In embodiments, the motor-generator 50 is an electric motor. The electric motor may be configured to drive rotation of the third driveshaft 54 when electric power is provided to the electric motor. Similarly, the electric motor may be configured to generate electric power when the second driveshaft 52 is rotated. The operation of the motor-generator 50 may be controlled by a controller of the control system 300 (which may be configured to control the delivery of electrical power to the motor-generator 50 and/or the drawing of power from the motor-generator 50).

The motor-generator 50 may be joined to the energy storage device 80, which may include a battery.

In some embodiments, the energy storage device 80 may be a kinetic energy storage device (such as a flywheel). The energy storage device 80 may be joined to the motor-generator 50 by a transmission part 82 (which may be a mechanical or electrical transmission part).

In embodiments, the energy storage device 80 may be configured to provide energy to one or more propulsive motor(s) of the vehicle 200 and, in some embodiments, at least one of the propulsive motor(s) may be an electric motor. This operation may be controlled by a controller of the control system 300.

The third driveshaft 54 of the motor-generator 50 may be configured to provide drive to other parts of the vehicle 200. In some embodiments, the third driveshaft 54 may be configured to provide mechanical power to (i.e. drive) one or more ancillaries or accessories 58, 60, 62, and 66 of the vehicle 200. In some embodiments, the third driveshaft 54 may be configured to provide mechanical power to a part of one or more ancillaries or accessories 58, 60, 62, and 66 of the vehicle 200 (for example, a compressor which is part of an air conditioning system of the vehicle 200). References to 'ancillaries' or 'accessories' 58, 60, 62, and 66 should be understood to include parts of one or more ancillaries or accessories 58, 60, 62 and 66. The APU 100 may include a drive coupling 56 which is configured to transfer mechanical power (i.e. drive) between the third driveshaft 54 and the one or more accessories and ancillaries 58, 60, and 66. The drive coupling 56 may be a pulley system, a gear system, and/or or a chain and sprocket system, or any combination of these or other suitable arrangement. The drive coupling 56 may be configured to transfer rotational motion of the third driveshaft 54 to rotational motion of a respective driveshaft (or other mechanical input member) associated with the or each ancillary or accessory 58, 60, and 66. In some embodiments, the drive coupling 56 may be further configured to provide a one-to-one, reduction, or overdrive ratio between the rotation of the third drive shaft 54 and the rotation of a respective driveshaft associated with the or each ancillary or accessory 58, 60, and 66. As such, the rate of rotation of the second driveshaft 54 may be translated by the drive coupling 56 (in some embodiments) into a different rate of rotation in a driveshaft associated with at least one of the one or more ancillaries or accessories 58, 60, and 66.

In some embodiments, one or more of the one or more ancillaries or accessories 58, 60, 62, and 66 may be configured to disengage at least partially from the drive coupling 56 - see the first ancillary or accessory 66 in particular. Accordingly, one or more of the one or more ancillaries or accessories 58, 60, 62, and 66 may be coupled to a selectively engageable part 64 (e.g. a clutch) which is configured to engage and disengage the drive coupling 56 selectively (to engage and disengage the associated ancillary or accessory 58, 60, 62, and 66 from the drive coupling 56). When disengaged, rotational motion of the third driveshaft 54 is not transmitted to the driveshaft associated with that ancillary or accessory 58, 60, 62, and 66.

In embodiments, at least one of the accessories or ancillaries 58, 60, 62, and 66 may be coupled directly to the third driveshaft 54 of the motor-generator 50 - which may be a direct coupling of the third driveshaft 54 to driveshaft associated with that ancillary or accessory 58, 60, 62, and 66 (see second ancillary or accessory 62 in particular). A direct coupling may be without use of the drive coupling 56. The direct coupling may be via one or more gears, belts, and/or pulleys (for example) or may be a fully direct coupling (without any intermediate gears, belts, and/or pulleys of the like). As will be understood, the directly coupled second ancillary or accessory 62 may be coupled via a selectively engageable part 64 (e.g. a clutch) in some embodiments.

It will be appreciated that the accessories or ancillaries 58, 60, 62, and 66 may be partially or completely disengaged from the drive coupling 56 and/or the third driveshaft 54 using the selectively engageable part (or parts) 64, such that the accessories or ancillaries 58, 60, 62, and 66 are each run at a desired speed. In some embodiments, the accessories or ancillaries 58, 60, 62, and 66 may include a hydraulic pump, an air conditioning compressor, an alternator, an air compressor, and/or a coolant pump. The or each ancillary or accessory 58, 60, 62, and 66 may be configured to convert the rotational movement of its associated driveshaft into a change of pressure in a fluid associated with the ancillary or accessory 58, 60, 62, and 66, a flow of electrical power through a circuit associated with the ancillary or accessory 58, 60, 62, and 66, or a fluid flow in the ancillary or accessory 58, 60, 62, and 66, for example.

Figure 2 shows an embodiment in a first condition, in which the second clutch part 48 is not engaged with the first clutch part 22.

Figure 3 shows an embodiment in a second condition, in which the second clutch part 48 is engaged with the first clutch part 22. Figure 4 shows the embodiment of figures 2 and 3, in use. In figure 4 (a first mode of operation), the energy storage device 80 is providing energy (as shown by arrow A) to the motor-generator 50 through transmission part 82. The energy is used by the motor-generator 50 to drive rotation of the third driveshaft 54 (and the second driveshaft 52 in some embodiments) in a first direction.

The rotational motion of the third driveshaft 54 is transmitted to the second ancillary or accessory 62, which has a direct coupling to the third driveshaft 54. The rotational motion of the third driveshaft 54 is also transmitted to the drive coupling 56. The drive coupling 56 transmits the rotational motion to third and fourth ancillaries or accessories 58 and 60.

The rotational motion is also transmitted to the selectively engageable part 64 (which, in figure 4, is in an engaged condition and therefore transmits rotational motion to the first ancillary or accessory 66).

In figure 4, the motor-generator 50 is behaving as an electric motor to provide rotational motion. The motor 10 may or may not be running and the first driveshaft 20 may or may not be rotating.

Figure 5 is similar to figure 4 as it shows the embodiment of figures 2 and 3 in use. In figure 5 (a second mode of operation), however, the selectively engageable part 64 is in a disengaged condition. Accordingly, rotational motion is not transferred to the first ancillary or accessory device 66 from the drive coupling 56.

In some embodiments, other ancillaries and accessories 58, 60, 62 may be coupled with one or more selectively engageable parts 64 (more than one ancillary and/or accessory may be coupled to the drive coupling 56 and/or third driveshaft 54 via a single selectively engageable part 64 in some embodiments), and it will be appreciated that any combination of these selectively engageable parts 64 may be in an engaged or disengaged condition at any one time. In some embodiments, the ancillaries or accessories 58, 60, 62, and 66 may be engaged or disengaged in groups. In some embodiments the ancillaries or accessories 58, 60, 62, and 66 may be disengaged according to a priority defined in the control system 300. In any event, it will be appreciated that the operation of the or each selectively engageable part 64 may be controlled by the control system 300.

Figure 6 shows the embodiment of figures 2 and 3 (in which the second clutch part 48 is engaged with the first clutch part 22) in use (a third mode of operation).

The motor 10, as shown in the condition in figure 6, operates to drive rotation of the first driveshaft 20. Rotation of the first driveshaft 20 drives rotation of the first clutch part 22 which transfers rotational motion to the second clutch part 48. Rotation of the second clutch part 48 transmits rotational motion to the second driveshaft 52.

The second driveshaft 52 drives rotational motion of the third driveshaft 54. Rotation of the second driveshaft 52 induces electrical power in the motor- generator 50, which provides power (as shown by arrow A) through the transmission part 82 to the energy storage device 80.

The rotational motion of second driveshaft 54 is transmitted via the drive coupling 56 or directly to the ancillaries or accessories 58, 60, 62, and 66. It will be appreciated that the ancillaries or accessories 58, 60, 62, and 66 may be engaged or disengaged, as discussed above, from the drive coupling 56. It will be appreciated that in figure 6, the motor-generator 50 is behaving as a generator, and that the rotation of the third driveshaft 54 is driven by the motor 10. In embodiments, the APU 100 may be actuated between the modes of operation of figure 4-7 under the control of the control system 300.

In embodiments, the control system 300 may be configured to change the mode of operation of the APU 100 in response to a status of the energy storage device 80, such as when the energy storage device 80 is in a depleted condition (i.e. storing less than a predetermined amount of energy).

Figure 7 shows the embodiment of figures 2 and 3 (in which the second clutch part 48 is engaged with the first clutch part 22), in another mode of use (a fourth mode of operation).

In the condition shown in figure 7, the motor 10 drives rotation of the first driveshaft 20. The first driveshaft 20 drives rotation of the second driveshaft 52 and third drive shaft 54 through the first clutch part 22 and the second clutch part 48.

The motor-generator 50 is also provided with power from the energy storage device 80 (as shown by arrow A) to drive rotation of the second 52 and third 54 driveshafts. Accordingly, the rotation of the second and third driveshafts 52,54 is driven by both the motor 10 and the motor-generator 50.

Such a mode of operation may be used when the accessories or ancillaries 58, 60, 62, and 66 are under particularly high load and so are taking more mechanical power from the third driveshaft 54 (via the drive coupling 56 or otherwise). This may slow the rotation of the third driveshaft 54 without additional power provided by the combined driving force of the motor 10 and the motor-generator 50.

In some embodiments, the first clutch part 22 may only engage the second clutch part 48 when the first driveshaft 20 is driven by the motor 10 and second driveshaft 52 is driven by motor-generator 50 at substantially the same rotational speed (and direction).

In some embodiments, the motor 10 and the motor-generator 50 may be substantially synchronised such that the first and second driveshafts 20,52 rotate at substantially the same speed (and direction) using the control system 300 (which may include the use of a controller of the motor 10 and a controller of the motor-generator 50). In some embodiments, the motor 10 and the motor-generator 50 may be substantially synchronised using the controller of either the motor 10 or the motor-generator 50. This may help to reduce vibration and improve durability. The control system 300 may be configured to substantially synchronise the motor 10 and the motor-generator 50 before the first and second driveshafts 20,52 are coupled (e.g. by engagement of the first and second clutch parts 22,48). The control system 300 may be configured such that the first and second driveshafts 20,52 are prevented from being coupled (e.g. by engagement of the first and second clutch parts 22,48) unless the motor 10 and motor-generator 50 are substantially synchronised. In some embodiments, on receiving a command to couple the first and second driveshafts 20,52 together, the control system 300 may be configured to substantially synchronise the motor 10 and the motor-generator 50 and, subsequently, to engage the first and second clutch parts 22,48. In some embodiments, the first clutch part 22 and the second clutch part 48 are configured to synchronise the motor 10 and the motor-generator 50 substantially as they engage. In some embodiments, the first driveshaft 20 may have little or no rotational motion when the first clutch part 22 is engaged with the second clutch part 48, and rotational motion may be transmitted from second driveshaft 52 (driven by the motor-generator 50) to the first driveshaft 20 - e.g. to start the motor 10. In some embodiments, the first driveshaft 20 or another shaft of the motor 10 may be provided with rotary motion by the starter motor 16 (which may be an electric motor which draws power from an electrical system of the vehicle 200 (such as the energy storage device 80 or some other energy storage device of the vehicle 200)). In some embodiments, rotational motion from the third driveshaft 54 may be used to drive one or more ground engaging wheels 202 of the vehicle 200. As such, the motor-generator 50 and/or the motor 10 may form the propulsive motor of the vehicle 200. As such, the APU 100 described herein may, in some embodiments, be more generally a power unit of the vehicle 200.

As will be appreciated, reference is made herein to rotation of various driveshafts and this rotation is with respect to another part of the vehicle (e.g. a body of the motor-generator 50 and/or motor). Embodiments of the present invention include an APU 100 with any combination of the above described ancillaries or accessories 58, 60, 62, and 66. In some embodiments, there is one ancillary or accessory 58, 60, 62, and 66. In some embodiments, there are two or more ancillaries or accessories 58, 60, 62, and 66. In some embodiments, there are three or more ancillaries or accessories 58, 60, 62, and 66. In some embodiments, there are four or more ancillaries or accessories 58, 60, 62, and 66. It will be appreciated, that the various modes of operation may be controlled by the control system 300 which may be automatic or manual or semi-automatic (i.e. requiring some operator input). The control system 300 may be part of the APU 100, may be separate from the APU 100, or at least part of the control system 300 may be part of the APU 100. The control system 300 may be part of a wider control system of the vehicle 200.

In some embodiments, the motor-generator driveshaft 52,54 is a through shaft which extends through the motor-generator 50 from one end thereof to the other. Each end of the through shaft may include an engagement formation suitable for engagement with other parts of the APU 100 (such as the second clutch part 48 and the drive coupling 56, for example). When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1 . A power unit for a vehicle, the power unit comprising:

a motor configured to drive rotation of a first driveshaft;

a motor-generator configured to drive rotation of a motor- generator driveshaft; and

an accessory or ancillary configured to be driven by the motor- generator driveshaft, wherein the first driveshaft and motor-generator driveshaft are selectively engageable such that rotation of the motor- generator driveshaft is driveable by the first driveshaft.

2. A power unit according to claim 1 , further comprising a control system which is configured to synchronise the speed of rotation of the first driveshaft and the motor-generator driveshaft before engagement of the first driveshaft and motor-generator driveshaft.

3. A power unit according to claim 1 or 2, wherein the motor is an internal combustion engine.

4. A power unit according to any preceding claim, wherein the motor- generator is an electric motor.

5. A power unit according to claim 4, wherein the motor-generator is configured to generate electricity when the first driveshaft is engaged with the motor-generator driveshaft and rotation of the motor-generator driveshaft is driven by the motor.

6. A power unit according to claim 5, further comprising an energy storage device which is configured to deliver electric power to the generator-motor in a mode of operation and to receive electric power from the generator- motor in another mode of operation.

7. A power unit according to any preceding claim, further comprising a first clutch part coupled for rotation with the first driveshaft and a second clutch part coupled for rotation with the motor-generator driveshaft, wherein the first driveshaft and the motor-generator driveshaft are engageable by engagement of the first and second clutch parts.

8. A power unit according to any preceding claim, wherein rotation of the motor-generator driveshaft is driveable by a combination of the both the motor and the motor-generator.

9. A power unit according to any preceding claim, wherein the accessory or ancillary is coupled to the motor-generator driveshaft by a drive coupling which is configured to be coupled to one or more further accessories or ancillaries.

10. A power unit according to any preceding claim, wherein the motor- generator driveshaft is a through shaft of the motor-generator.

1 1 . A power unit according to any preceding claim, wherein the power unit is an auxiliary power unit.

12. A power unit according to any of claims 1 to 10, wherein the motor- generator is configured to provide a propulsive force for a vehicle.

13. A vehicle including a power unit according to any of the preceding claims.

14. A vehicle according to claim 13, wherein the vehicle is a hybrid vehicle.

15. A vehicle according to claim 13 or 14, wherein the vehicle is a heavy goods vehicle.

16. A vehicle according to any of claims 13 to 15, wherein the vehicle is an aircraft, a boat, or a ship.

17. A power unit substantially as herein described with reference to the accompanying drawings.

18. A vehicle substantially as herein described with reference to the accompanying drawings.

19. Any novel feature or novel combination of features disclosed herein.