WO2015097457A1

WO2015097457A1 - Air conditioning system for an aircraft mover

Info

Publication number: WO2015097457A1
Application number: PCT/GB2014/053788
Authority: WO
Inventors: Tushar Kulkarni
Original assignee: Textron Ground Support Equipment Uk Limited
Priority date: 2013-12-24
Filing date: 2014-12-19
Publication date: 2015-07-02
Also published as: GB2516708A; GB201322977D0; GB2516708B

Abstract

An air conditioning system (32) for an aircraft mover (10) motively powered by a driving engine (28). The air conditioning system (32) comprises a supplementary internal-combustion engine (62), a hydraulically powerable compressor (38),an evaporator (40) and a condenser (42) fed by the hydraulically powerable compressor (38), at least one fan (48) associated with the evaporator (40) and powerable by a first electrical output (70) associated with the driving engine (28) and a second electrical output (72) associated with the supplementary internal-combustion engine (62), and a controller (74) for activating the supplementary internal-combustion engine (62), under at least idling stop of the driving engine (28). The supplementary internal-combustion engine (62) hydraulically powers the compressor (38) at substantially constant speed. The invention further relates to an aircraft mover (10) having such an air conditioning system (32), and also to a method of reducing the fuel consumption of an aircraft mover (10).

Description

Air Conditioning System For An Aircraft Mover

The present invention relates to an air conditioning system for an aircraft mover, more particularly but not necessarily exclusively being an aircraft tractor, motively powered by a driving engine. The air conditioning system includes a supplementary internal- combustion engine which can activate under an idling condition of the driving engine to power a hydraulically powerable compressor of the air conditioning system. The invention further relates to an aircraft mover having such an air conditioning system, and also to a method of reducing the fuel consumption of an aircraft mover using such an air conditioning system. It is well known to use the main engine of a vehicle to power an air conditioning system so as to moderate the temperature of the driver, passengers or cargo. However, if air conditioning is required when the vehicle is stationary, the engine must idle in order to generate power for the air conditioning unit. This has many negative effects.

An idling engine wastes a considerable amount of fuel when idling, in addition to producing excess environmentally-harmful waste gases, carbon dioxide in particular along with other undesirable noxious or toxic substances. Furthermore, vehicles which are required to idle for significant amounts of time require more frequent maintenance than vehicles which operate normally, thus increasing overall running costs.

For heavy-duty vehicles, there may be long periods in which the vehicle is not required to be operational, but where the driver must remain on standby in the vehicle. For instance, an aircraft tractor might idle for considerable durations whilst awaiting permission from air traffic control to approach a runway or docked aircraft. In both hot and cold environments, the driver may require the air conditioning and heating to be respectively active in order to remain comfortable in a cab of the tractor during this period.

Particularly, when on standby or at idling stop, the driving engine of the aircraft mover may be raced by the operator to increase its rpm and thus increase the speed of the compressor of the traditional on-board air-conditioning system, thereby achieving greater cooling. This is particularly prevalent in hotter climates, but leads to greater engine wear and thus increased maintenance intervals along with significantly increased fuel usage.

It is also known from buses to use a secondary dedicated engine purely to provide power to an associated independent air conditioning system in order to cool the occupants being transported. However, such a system requires two engines to be simultaneously operational if power is required for both the drive of the engine and the drive of the compressor. This arrangement greatly increases fuel usage, and a wholly separate air conditioning system has to be accommodated within the vehicle.

It is an object of the present invention to obviate or substantially overcome these problems.

According to a first aspect of the present invention, there is provided an air conditioning system for an aircraft mover motively powered by a driving engine, the air conditioning system comprising a supplementary internal-combustion engine having a lower power capacity than the driving engine, a hydraulically powerable compressor drivable by the supplementary internal-combustion engine and the driving engine, an evaporator and a condenser fed by the hydraulically powerable compressor, at least one fan associated with the evaporator and powerable by a first electrical output associated with the driving engine and a second electrical output associated with the supplementary internal-combustion engine, and a controller for activating the lower-power supplementary internal-combustion engine, under at least idling stop of the driving engine, to hydraulically power the compressor at constant or substantially constant speed.

Typical air conditioning units for heavy vehicles, such as aircraft movers, use a belt- driven compressor, driven from a driving engine of the vehicle, to power the compressor of the air conditioning system. This means that the efficiency of the air conditioning system is dependent upon the speed of the engine. If the engine is idling, the air conditioning will begin to fail or be unable to meet a cooling demand and a driver or operator will be required to engage or race the engine to increase its idle speed in order to remain comfortable. This results in significant levels of fuel wastage and increased maintenance and repair costs. By providing a system which is able to recognise when the driving engine is idling or stopped, and thus activate a smaller-displacement supplementary internal-combustion engine accordingly, the air conditioning system can be run at maximum capacity at all times, whilst never or rarely requiring two engines to be running simultaneously, at least for extended periods. As the supplementary internal-combustion engine provided is considerably smaller than the driving engine in terms of power capacity and/or displacement, having typically for example one tenth of the power output, the fuel consumption of the aircraft mover is significantly reduced when the driving engine is under idling stop or switched off. Preferably, the controller may include a hydraulic-pressure monitoring device for monitoring hydraulic pressure being supplied to the hydraulically powerable compressor, the supplementary internal-combustion engine being activatable when the hydraulic pressure from the driving engine falls below a predetermined parameter.

The system may further comprise air conditioning activation means and driving engine activation means, the controller automatically activating the supplementary internal- combustion engine in response to both a deactivation output from the driving engine activation means and an activation output from the air conditioning activation means.

Optionally, the supplementary internal-combustion engine may be controllable by the controller to operate at a constant or substantially constant speed providing a constant or substantially constant hydraulic power output for a maximum capacity of the compressor. It is advantageous to avoid any drop in output of the air conditioning system, to ensure continued comfort for the driver of the aircraft mover.

Preferably, the controller may further include a switchable hydraulic valve having first and second hydraulic inlet ports communicable with respective hydraulic outputs associated with the driving engine and the supplementary internal-combustion engine, and a hydraulic outlet port in hydraulic communication with the compressor.

The system may further comprise a hydraulic generator powerable by the driving engine and the supplementary internal-combustion engine and by which the hydraulic compressor is drivable. Preferably, the controller may further include a timer unit for delaying switching from the driving engine pending activation of the supplementary internal-combustion engine, and additionally or alternatively may further include a switch unit for switching between the electrical outputs associated with the driving engine and the supplementary internal-combustion engine and feeding the said at least one fan.

The system may, in a preferred embodiment, further comprise at least one further fan associated with the condenser of the air conditioning system.

Advantageously, a common fuel reservoir may be further provided in communication with the driving engine and the supplementary internal-combustion engine. The electrical output associated with the supplementary internal-combustion engine may be in electrical communication with a charging unit of a battery pack, the said at least one fan being energisable by the supplementary internal-combustion engine through the battery pack.

Optionally, the driving engine may be a compression-ignition internal-combustion engine.

According to a second aspect of the invention, there is provided an aircraft mover for moving an aircraft, the aircraft mover comprising a wheeled chassis, a driving engine mounted on the wheeled chassis and for motively powering the aircraft mover, aircraft engagement means for releasably engaging an aircraft for manoeuvring, and an air conditioning system in accordance with the first aspect of the invention.

Preferably, the aircraft mover is an aircraft tractor including a cab for a driver on the wheeled chassis.

It is advantageous to provide an aircraft mover having an air conditioning system in accordance with the first aspect of the invention, given that aircraft movers spend considerable periods awaiting instructions from air traffic control or ground staff. The tarmac of the runway can often reach very high temperatures, especially in hot countries, and maximum air conditioning for the driver may be required constantly. To reduce fuel consumption, therefore, the aircraft mover can be installed with the air conditioning system of the first aspect of the invention, providing automatic switching to powering the compressor of the air conditioning system from the supplementary internal-combustion engine when the drive engine is idling or even stopped. According to a third aspect of the invention, there is provided a method of reducing fuel consumption of an air-conditionable aircraft mover using an air conditioning system in accordance with the first aspect of the invention, the method comprising the step of utilising a supplementary internal-combustion engine having a lower power capacity than a driving engine providing motive power to the aircraft mover, and controlling the supplementary internal-combustion engine to operate at a predetermined constant or substantially constant power output, when switched from the driving engine due to at least an idling stop condition, to hydraulically power a hydraulic compressor of the air conditioning system at constant or substantially constant speed, whereby compressor speed becomes independent of the speed of the driving engine in non-aircraft- manoeuvring conditions.

Providing a method of reducing fuel consumption of an aircraft mover by utilising a supplementary internal-combustion engine to power a hydraulic compressor of an onboard air conditioning system when the driving engine is under at least an idling stop or deactivated will advantageously reduce the cost of running the aircraft mover. The method also advantageously provides for maximum running of the hydraulic compressor without further driver interaction, once the air conditioning system has been activated and without the need for revving of the driving engine.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a diagrammatic representation of one embodiment of an air conditioning system within the front of an aircraft mover, in accordance with the first aspect of the invention; Figure 2 shows a diagrammatic representation of a power supply from the driving and supplementary internal combustion engines of an aircraft mover, in accordance with the first aspect of the invention;

Figure 3 is a perspective view of one embodiment of an aircraft tractor having the air conditioning system of Figure 1, in accordance with the second aspect of the invention; and

Figure 4 diagrammatically depicts the interaction of the components of the air conditioning system of Figure 1.

With reference firstly to Figures 1 to 3, there is shown an aircraft mover 10, in this case being an aircraft tractor, having a chassis 12, a plurality of wheels 14, and a cab 16 for an operator 18 of the mover 10 located at the front end 20 of the chassis 12 At least one fuel tank 22 is also provided, along with aircraft engagement means 24 located at a rear end 26 of the chassis 12. The aircraft mover 10 is motively powered by a driving engine 28, which is in this case a diesel engine, drawing fuel from the fuel tank 22 and being located forwardly within the chassis 12. Within the cab 16, there is at least a driving engine activation means 30 for starting at least the driving engine 28. In this case, there is an ignition key or switch for starting the diesel engine.

Although a compression-ignition internal combustion driving engine 28 is suggested, other kinds of engine aside from diesel powered can be considered, such as a spark- ignition internal combustion engine utilising, for example, petrol or gasoline, or a turbine engine.

There is provided in the aircraft mover 10 an air conditioning system 32, which may also be located forwardly within the chassis 12. The air conditioning system 32 comprises a closed circuit within which a heat-transfer fluid is circulated in order to provide conditioned air to the cab 16 via one or more ducts 34 and associated vents 36.

The closed circuit comprises at least a hydraulically powerable compressor 38 and an evaporator 40 fed by the compressor 38. Typically, the closed circuit would also comprise a condenser 42, an expansion valve 44 and a drier 46, thereby providing both heating and cooling functionality for the air conditioning system 32. There may also be further provided one or more electrically powered heaters 47 to provide heating independently of air conditioning.

Generally, the circuit is constructed with the compressor 38 feeding high pressure gaseous fluid to the condenser 42, providing a heating effect during condensation. The condenser 42 then in turn feeds the drier 46 with high pressure liquid having condensed in the condenser 42. The high pressure liquid then passes into the expansion valve 44, reducing the pressure of the liquid. This passes then to the evaporator 40, wherein the liquid evaporates into a low pressure gas, which cools the surrounding air. The evaporator 40 feeds back into the expansion valve 44, which then supplies the low pressure gas to the compressor 38 for pressurisation.

To facilitate air flow through the ducts 34 and vents 36, there is provided at least an evaporator fan 48, and preferably also a condenser fan 50, associated respectively with the evaporator 40 and condenser 42.

Much of the closed circuit is enclosed within an air conditioning matrix 52 at or adjacent the cab 16. Preferably, the condenser 42 and condenser fan 50 are mounted forwardly upon the chassis 12, a said duct 34 feeding the air conditioning matrix 52. The compressor 38 is preferably located adjacent the driving engine 28. The remaining components of the closed circuit may then be preferably contained within the air conditioning matrix 52. On or adjacent the air conditioning matrix 52 within the cab 16 may be a control panel 54 for the air conditioning system 32. From the control panel 54, the functionality of the air conditioning system 32 may be controlled by the operator 18. The control panel 54 preferably includes at least air conditioning activation means 56 for activating and deactivating the air conditioning system 32, and preferably also temperature control means 58 and air flow control means 60. These various means may typically be in the form of mechanical and/or electronic switches, sliders and/or automatic sensors.

The compressor 38 is powerable by both the driving engine 28 and a supplementary internal-combustion engine 62. The supplementary internal-combustion engine 62 is also preferably located forwardly within the chassis 12. The supplementary internal- combustion engine 62 has a lower power capacity than the driving engine 28, its only function being for powering the air conditioning system 32. The supplementary internal-combustion engine 62 may also draw fuel from the same fuel tank 22 as the driving engine 28, beneficially dispensing with the need for a dedicated supplementary fuel tank, and thus saving space on the chassis and installation costs.

Both the driving engine 28 and supplementary internal-combustion engine 62 are adapted to provide hydraulic power to the compressor 38. They may either generate the hydraulic power themselves, or may mechanically drive at least one hydraulic generator. Regardless of how the hydraulic power is generated, there is a first hydraulic output 64 associated with the driving engine 28 and a second hydraulic output 66 associated with the supplementary internal combustion engine 62 which supply hydraulic power to the compressor 38.

The advantages of a hydraulically driven compressor 38 over a belt-driven compressor are that the compressor speed is independent of the rotational speed of the driving engine 28. In presently available vehicular air conditioning systems having belt-driven compressors, a decrease in the speed of the driving engine will accordingly lead to a decrease in the capacity of the air conditioning system as the mechanically connected compressor slows. Therefore, the cab of the vehicle can quickly reach an uncomfortable temperature when the driving engine is under idling stop or halted altogether. The driving engine 28 and supplementary internal-combustion engine 62 are both also capable of generating electrical energy, which can be used to provide electricity to the components of the air conditioning system 32 requiring electrical powering, such as the evaporator and condenser fans 48, 50. The electricity may be generated directly by the engines 28, 62, for instance, using respective or a common alternator 68, or alternatively, there may be provided an electrical generator which can be mechanically driven by the or each engine 28, 62, which can in turn provide the electricity. Where electrically-powered heaters 47 are also provided, the electrical energy generated may preferably be used to power these as well. Regardless of how the electricity is generated, there is provided a first electrical output 70 associated with the driving engine 28 and a second electrical output 72 associated with the supplementary internal-combustion engine 62.

There is further provided a controller 74 for activating and deactivating the supplementary internal combustion engine 62 as necessary, though the controller 74 could readily be applied to have other additional control functionality. The controller 74 may comprise: a switchable hydraulic valve 76 for selecting the source of the hydraulic power supplied to the compressor 38; a timer unit 78 for providing a delay before switching from the first hydraulic output 64 of the driving engine 28 to the second hydraulic output 66 of the supplementary internal combustion engine 62, pending activation of the supplementary internal combustion engine 62; and a switch unit 80 for switching between providers of electrical energy for the evaporator and condenser fans 48, 50, in this case being the driving engine 28 and the supplementary internal combustion engine 62.

The controller 74 is therefore in communication with at least the supplementary internal combustion engine 62, thereby providing activation and deactivation signals, and preferably also in communication with the hydraulic valve 76 and a hydraulic-pressure monitoring device 82.

The switchable hydraulic valve 76 may include first and second hydraulic inlet ports 84, 86 which receive hydraulic power from the first and second hydraulic outputs 64, 66. The valve 76 further includes a hydraulic output port 88, which is in hydraulic communication with the compressor 38. The hydraulic valve 76 is capable of switching between receiving hydraulic power from first and second hydraulic inlet ports 84, 86. The hydraulic valve 76 can open the first hydraulic inlet port 84, enabling hydraulic communication with the hydraulic output port 88, whilst simultaneously closing the second hydraulic inlet port 86. When switched, the hydraulic valve 76 closes the first hydraulic inlet port 84, whilst opening the second hydraulic inlet port 86, thus enabling hydraulic communication between the second hydraulic inlet port 86 and the hydraulic output port 88.

The controller 74 preferably communicates with the hydraulic-pressure monitoring device 82 for monitoring the hydraulic pressure being supplied to the compressor 38. This may be mounted in hydraulic communication with the first hydraulic output 64 of the driving engine 28, thereby measuring the hydraulic pressure generated by the driving engine 28.

In the aircraft mover 10, there may also be provided a battery pack 90, the battery pack 90 being charged via a charging module 92 from the first electrical output 70 of the driving engine 28 and the second electrical output 72 of the supplementary internal combustion engine 62. The battery pack 90 may further be in electrical communication with at least the evaporator and condenser fans 48, 50, thereby providing the electrical power to operate the fans 48, 50. Whilst in the depicted embodiment, a battery pack 90 is shown, any appropriate electrical energy storage means could be used, such as a bank of fuel cells, for instance.

Advantageously, the supply of electricity to the evaporator and condenser fans 48, 50 can be controlled from the controller 74, such that switching the hydraulic powering of the compressor 38 can simultaneously switch between first and second electrical outputs 70, 72 leading to the battery pack 90.

Aircraft movers 10 are used to move aircraft around the runway, terminal and hanger areas of an airport or maintenance facility, as well as to loaders for offsite maintenance and repair facilities. In between these operations, however, the aircraft mover 10 will not necessarily be required to be operational. During these non-operational periods, the operator 18 may still require air conditioning of the cab 16, either with the driving engine 28 at idling stop or not running.

An aircraft mover 10 may be used in a variety of environmental conditions. Airports are built in diverse locations, ranging from deserts to arctic tundra. The air conditioning system 32 must therefore be robust enough to keep the operator 18 comfortable in both hot and cold conditions during non-operational periods. It is advantageous therefore to minimise fuel consumption of the air conditioning system 32.

In use, the operator 18 may turn on the aircraft mover 10 with the driving engine activation means 30, starting the driving engine 28. The operator 18 may then drive the aircraft mover 10 as normal. When air conditioning is required, the operator 18 activates the air conditioning activation means 56 on the control panel 54. This sends a signal to the controller 74 to activate the compressor 38.

The hydraulic power required to run the compressor 38 at maximum capacity is predetermined, and programmed into the controller 74. The hydraulic-pressure monitoring device 82, being in communication with the first hydraulic output 64 of the driving engine 28, relays a measured hydraulic pressure to the controller 74. Assuming that the aircraft mover 10 is operating under normal conditions, the driving engine 28 outputs sufficient hydraulic power to run the compressor 38 at maximum capacity, and therefore the hydraulic pressure measured will be above the predetermined threshold. With reference to Figure 4, the controller 74 will send a signal via its switch unit 80 to the hydraulic valve 76, and hydraulic power will be transmitted from the driving engine 28 to the compressor 38. The compressor 38 will operate, pressurising and transporting the fluid around the air conditioning system 32.

The condensation and subsequent evaporation of the fluid within the condenser 42 and evaporator 40 generates the cooling and heating for the air conditioning system 32 respectively. The evaporator and condenser fans 48, 50 transfer the conditioned air through the ducts 34 of the air conditioning system 32 to the cab 16. The electric power to drive these fans 48, 50 is provided from the battery pack 90, the battery pack 90 being charged from the first electrical output 70 of the driving engine 28 via the charging module 92.

When the normal operation of the aircraft mover 10 is no longer required, for instance when the aircraft mover 10 is awaiting instructions, the driving engine 28 will be under idling stop. Subsequently the hydraulic pressure measured at the first hydraulic output 64 of the driving engine 28 by the hydraulic-pressure monitoring device 82 will drop below the predetermined threshold.

Once the hydraulic pressure has dropped, the controller 74 preferably sends two signals; one to the supplementary internal-combustion engine 62 and one to the hydraulic valve 76. The signal to the supplementary internal-combustion engine 62 is an activation signal, causing the supplementary internal-combustion engine 62 to begin generating hydraulic power. The signal to the hydraulic valve 76 passes through the timer unit 78, adding a delay to allow the supplementary internal-combustion engine 62 time to generate sufficient power to drive the compressor 38 at, preferably maximum, capacity prior to switching. After the delay, the signal triggers the hydraulic valve 76 to switch, opening the second hydraulic inlet port 86, that is, the port associated with the supplementary internal-combustion engine 62, and closing the first hydraulic inlet port 84, that is, the port associated with the driving engine 28.

Once the supplementary internal-combustion engine 62 is activated, it will also begin to generate electricity. To this end, the second electrical output 72 of the supplementary internal-combustion engine 62 also provides electrical power to the charging module 92 of the battery pack 90, which can then in turn provide power to the evaporator and condenser fans 48, 50.

As the aircraft mover 10 is required to operate normally once more, the hydraulic pressure output of the driving engine 28 will rise above the predetermined threshold again. This will register with the hydraulic-pressure monitoring device 82, triggering the controller 74 to send signals to both the supplementary internal-combustion engine 62 and the hydraulic valve 76.

The supplementary internal-combustion engine 62 is thus sent a deactivation signal from the controller 74, and as such, it ceases to supply hydraulic power to the compressor 38 or electricity to the charging modules 92 of the battery pack 90. The signal sent to the hydraulic valve 76 is sent directly, with no requirement for a delay to be issued from the timer unit 78. The hydraulic valve 76 thus switches, closing the second hydraulic inlet port 86, that is, the port associated with the supplementary internal-combustion engine 62, and opening the first hydraulic inlet port 84, that is, the port associated with the driving engine 28

The switching process can thus occur as many times as necessary during the operation of the aircraft mover 10, such that the air conditioning system 32 may be continuously operable, with the compressor 38 remaining at maximum or substantially maximum capacity. As a result of this switching, the supplementary internal-combustion engine 62 is preferably only in use during idling stop of the driving engine 28. The two engines 28, 62 are not therefore operational in unison, particularly over any extended period of time. Since the supplementary internal-combustion engine 62 is much smaller in terms of power output than the driving engine 28, there is a much reduced fuel consumption associated with the air conditioning system 32 during idling stop of the driving engine 28, and therefore, there is an associated reduction in ongoing costs for the aircraft mover 10.

Figure 4 also includes the option of running the air conditioning system whilst the driving engine 28 is halted. It is not preferred that the air conditioning system 32 can be operated if the operator is absent from the cab, since this can result in wasted energy and fuel due to the system 32 remaining accidentally or unintentionally active. However, in an idle condition where, for example, the driving engine 28 may benefit from being deactivated or not running, for example, by the use of 'stop-start' engine technology to improve fuel economy, and where the operator remains in the cab, it is feasible that the supplementary internal-combustion engine 62 can be energised and thus the air conditioning system 32 operational to control a cab environment.

It will be noted that the switching is not independent of the running of the aircraft mover 10; the activation signal sent to the supplementary internal-combustion engine 62 will not be sent if the aircraft mover 10 is entirely non-operational. Therefore, the controller 74 may be capable of receiving a signal from the driving engine activation means 30 which overrides the activation signal sent as a result of the drop in hydraulic pressure measured by the hydraulic-pressure monitoring device 82.

A key feature of the air conditioning system 32 is the ability to operate the compressor 38 at or substantially at maximum capacity regardless of the output power of the driving engine 28. This means that there may never be a requirement of any input from the operator 18 to maintain the level of air conditioning within the cab 16, other than via access through the control panel 54. For instance, the operator 18 may not be required to power the driving engine 28 unnecessarily to maintain the speed of the compressor 38 to achieve comfortable in-cab air temperatures. This results in potentially significant reductions in fuel usage, costs and waste gas emission, as well as a reduction in periodic maintenance of the driving engine.

Whilst the air conditioning system 32 as described is a main inventive concept, it is noted that there are situations in which it would be preferable to use the heater 47. For instance, in cold, dry climates, there may be no need for the dehumidification of air provided by an air conditioning system 32. Therefore, less energy is wasted if a specific heating unit is used.

It is thus possible to provide a heating system for an aircraft mover 10 powerable by the driving engine 28, the heating system including the supplementary internal-combustion engine 62 having a lower power capacity than the driving engine 28, and heating means for providing heated air to a cab 16 of the aircraft mover 10.

Such heating means could be provided in concert with the air conditioning system 32 in accordance with the first aspect of the invention, or could be provided separately if necessary, and thus the remainder of the air conditioning system may be dispensed with. For instance, the heating means could be heated coolant diverted from the driving engine 28, conductively heating a heater core, typically provided in the air conditioning matrix 52 near the evaporator 40, which will radiatively heat the surrounding air. However, such a solution requires the driving engine 28 to be active at all times when heat is required, in order to pump the heated coolant. Alternatively, the electrically powered heater 47 is preferably the heating means. This heater 47 can be used in concert with the air conditioning system 32 or can act independently. Critically, the electrically powered heater 47 does not necessarily have to be powered by the driving engine 28. Therefore, the heater 47 can conveniently be powered from the battery pack 90, the source of the electrical energy charging the battery pack 90 via the charging module 92 being switchable in an analogous manner to the way in which the fans 48, 50 of the evaporator and condenser 40, 42 are powered in the previously described embodiment.

Assuming that the heater 47 is activated, if the driving engine activation means 30 is deactivated, the supplementary internal-combustion engine 62 may be activated by the controller 74 to provide a constant source of electrical energy to the battery pack 90 via the charging module 92. If the driving engine activation means 30 is activated, then the supplementary internal-combustion engine 62 may be deactivated by the controller 74, and the driving engine 28 may instead provide the electrical energy directly for power and/or recharging of the battery pack 90. The remainder of the air conditioning system described above may thus be omitted, as necessity dictates.

The signal to switch sources of electrical energy may also be triggered by a change in the hydraulic pressure of the first hydraulic output 64 of the driving engine 28. If the hydraulic pressure drops below a predetermined threshold, the controller 74 may activate the supplementary internal-combustion engine 62, and may deactivate the supplementary internal-combustion engine 62 if the hydraulic pressure rises above the predetermined threshold.

Irrespective as to whether the battery pack 90 is providing electrical energy for the evaporator fan 48 and compressor fan 50, the heater 47, or any combination thereof, installation of the supplementary internal-combustion engine 62 to be activated automatically during at least an idling stop of the driving engine 28 ensures a constant charging of the battery pack 90 via the charging module 92.

It will be appreciated that the above description merely describes only one possible implementation of the present invention, and that alternative embodiments could be conceived without deviating from the overall inventive concept.

For instance, whilst the invention has been specifically described for an aircraft mover, in particular an aircraft tractor, the requirement for operation of the air conditioning system is the presence of a hydraulically driven compressor being automatically selectably driven by the driving engine or a supplementary internal-combustion engine. Any vehicle having these components could conceivably install an air conditioning system according to the present invention. Therefore, although there is provided an air conditioning system which is ideally suited for an aircraft mover, it is in no way intended to be exclusively for such use and should be considered suitable for any vehicle motively powered by a driving engine. Furthermore, although the supplementary engine is described as being an internal- combustion engine, it will be appreciated that providing the hydraulic power to the compressor is the significant requirement, rather than the method of generating the power. Other types of engine could therefore be considered, as explained above. The air conditioning system has hereto before been described as being an integral part of the aircraft mover. However, such a system can easily be retro-fitted to existing models of aircraft mover and potentially other engine-driven vehicles, in order to achieve the benefits with respect to fuel efficiency and reduced maintenance costs.

There is therefore provided an air conditioning system for an aircraft mover which utilises a secondary internal-combustion engine and a hydraulically powered compressor variably powerable by either the driving engine or the secondary internal- combustion engine. By utilising the lower power secondary engine to supplement the driving engine, drive to the compressor by the driving engine can be substituted for drive from the secondary engine, particularly under idling stop conditions or low power requirement situations of the driving engine.

It is also beneficial that the switching between the driving engine and the supplementary internal-combustion engine is controlled by a controller, which may determine whether to switch based on a feedback from a hydraulic-pressure monitoring device, monitoring the hydraulic output of the driving engine. The switching may also switch the source of electrical power, powering at least an evaporator fan of the air conditioning system, from the driving engine to the supplementary internal-combustion engine.

The words 'comprises/comprising' and the words 'having/including' when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components, but does not preclude the presence of addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of this invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as herein described.

Claims

1. An air conditioning system (32) for an aircraft mover (10) motively powered by a driving engine (28), the air conditioning system (32) comprising a supplementary internal-combustion engine (62) having a lower power capacity than the driving engine (28), a hydraulically powerable compressor (38) drivable by the supplementary internal-combustion engine (62) and the driving engine (28), an evaporator (40) and a condenser (42) fed by the hydraulically powerable compressor (38), at least one fan (48) associated with the evaporator (40) and powerable by a first electrical output (70) associated with the driving engine (28) and a second electrical output (72) associated with the supplementary internal-combustion engine (62), and a controller (74) for activating the lower-power supplementary internal-combustion engine (62), under at least idling stop of the driving engine (28), to hydraulically power the compressor (38) at constant or substantially constant speed.

2. An air conditioning system (32) as claimed in claim 1, wherein the controller

(74) includes a hydraulic-pressure monitoring device (82) for monitoring hydraulic pressure being supplied to the hydraulically powerable compressor (38), the supplementary internal-combustion engine (62) being activatable when the hydraulic pressure from the driving engine (28) falls below a predetermined parameter.

3. An air conditioning system (32) as claimed in claim 1 or claim 2, further comprising air conditioning activation means (56) and driving engine activation means (30), the controller (74) automatically activating the supplementary internal-combustion engine (62) in response to both a deactivation output from the driving engine activation means (30) and an activation output from the air conditioning activation means (56).

4. An air conditioning system (32) as claimed in any one of claims 1 to 3, wherein the supplementary internal-combustion engine (62) is controllable by the controller (74) to operate at a constant or substantially constant speed providing a constant or substantially constant hydraulic power output for a maximum capacity of the compressor (38).

5. An air conditioning system (32) as claimed in any one of the preceding claims, wherein the controller (74) further includes a switchable hydraulic valve (76) having first and second hydraulic inlet ports (84, 86) communicable with respective hydraulic outputs (64, 66) associated with the driving engine (28) and the supplementary internal-combustion engine (62), and a hydraulic outlet port (88) in hydraulic communication with the compressor (38).

6. An air conditioning system (32) as claimed in any one of the preceding claims, further comprising a hydraulic generator powerable by the driving engine (28) and the supplementary internal-combustion engine (62) and by which the hydraulic compressor (38) is drivable.

7. An air conditioning system (32) as claimed in any one of the preceding claims, wherein the controller (74) further includes a timer unit (78) for delaying switching from the driving engine (38) pending activation of the supplementary internal-combustion engine (62).

8. An air conditioning system (32) as claimed in any one of the preceding claims, wherein the controller (74) further includes a switch unit (80) for switching between the electrical outputs (70, 72) associated with the driving engine (28) and the supplementary internal-combustion engine (62) and feeding the said at least one fan (48).

9. An air conditioning system (32) as claimed in any one of the preceding claims, further comprising at least one further fan (50) associated with the condenser (42) of the air conditioning system (32).

10. An air conditioning system (32) as claimed in any one of the preceding claims, further comprising a common fuel reservoir in communication with the driving engine (28) and the supplementary internal-combustion engine (62).

11. An air conditioning system (32) as claimed in any one of the preceding claims, wherein the electrical output (72) associated with the supplementary internal- combustion engine (62) is in electrical communication with a charging unit of a battery pack, the said at least one fan (48) being energisable by the supplementary internal-combustion engine (62) through the battery pack.

12. An air conditioning system (32) as claimed in any one of the preceding claims, wherein the driving engine (28) is a compression-ignition internal-combustion engine (62).

13. An aircraft mover (10) for moving an aircraft, the aircraft mover (10) comprising a wheeled chassis (12), a driving engine (28) mounted on the wheeled chassis (12) and for motively powering the aircraft mover (10), aircraft engagement means (24) for releasably engaging an aircraft for manoeuvring, and an air conditioning system (32) as claimed in any one of the preceding claims.

14. An aircraft mover (10) as claimed in claim 13, which is an aircraft tractor including a cab (16) for a driver on the wheeled chassis (12).

15. A method of reducing fuel consumption of an air-conditionable aircraft mover (10) using an air conditioning system (32) as claimed in any one of claims 1 to 12, the method comprising the step of utilising a supplementary internal- combustion engine (62) having a lower power capacity than a driving engine (28) providing motive power to the aircraft mover (10), and controlling the supplementary internal-combustion engine (62) to operate at a predetermined constant or substantially constant power output, when switched from the driving engine (28) due to at least an idling stop condition, to hydraulically power a hydraulic compressor (28) of the air conditioning system (32) at constant or substantially constant speed, whereby compressor speed becomes independent of the speed of the driving engine (28) in non-aircraft-manoeuvring conditions.