WO2017068338A1

WO2017068338A1 - Compressed air systems and methods

Info

Publication number: WO2017068338A1
Application number: PCT/GB2016/053234
Authority: WO
Inventors: Daniel HYDEN; Jonathan Wilson; Kevin Scott
Original assignee: Alexander Dennis Limited
Priority date: 2015-10-18
Filing date: 2016-10-18
Publication date: 2017-04-27
Also published as: GB201808037D0; GB2558852A; GB201518409D0; GB2558852B

Abstract

There is described compressed air system (300) and methods for vehicles, and in particular passenger service vehicles (100, 200). Such systems (300) may comprise at least one service reservoir (320) for providing compressed air to a particular vehicle system (310), and may also comprise a compressor system (330) for supplying compressed air to the service reservoir (320). The compressor system (300) may be configured to be operable between an operational state and an non-operational state based on air pressure control signals received at the compressor system. The system may also comprise a controller (380) configured to observe particular driving conditions of the vehicle, and to communicate particular air pressure control signals to the compressor system (330) based on the observed driving conditions.

Description

Compressed Air Systems and Methods

Technical Field

The invention relates to the field of compressed air systems, controllers and methods for vehicle compressor systems, particularly those used with passenger service vehicles, and the like.

Background As used herein, the term "passenger service vehicle" encompasses vehicles for transporting passengers and, in particular, road vehicles for transporting passengers. Exemplary passenger service vehicles may be buses, coaches or the like.

Significant innovation and technology development has occurred in recent years in relation to passenger service vehicles. In particular, there has been a continued drive towards providing vehicles that have low running costs, and improved fuel efficiency, etc., while at the same time maintaining or improving the safety of those vehicles.

Many passenger service vehicles comprise compressed air systems that are used to provide pressurised air to vehicle subsystems, such as the brakes, suspension or the like. The compressed air systems can often be powered by the engine, and so optimising the use of such systems can have an effect on the overall fuel efficiency of the vehicle. Further, and as with most vehicle components, such compressed air systems can be prone to degradation over time and so have a limited lifespan. Therefore, improving the usage of such systems may improve the lifespan, and thus reduce running and maintenance costs, while also reducing vehicle downtime (i.e. time not in service).

This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues.

Summary

In some examples, there are described compressed air systems, controllers and methods for vehicles, such as passenger service vehicles. The described systems, controllers and methods may help improve fuel efficiency, and in some cases reduce running costs, maintenance costs, and vehicle downtime.

In one example, there is described a compressed air system for providing compressed air to one or more particular vehicle systems. For example, the vehicle systems may include one or more braking system, suspension system, or the like. The compressed air system may comprise at least one service reservoir for providing compressed air to particular vehicle systems.

The compressed air system may comprise a compressor system for supplying compressed air to the vehicle systems (e.g. to the service reservoir, and to the vehicle systems). The compressor system may comprise at least one compressor and at least one air processing unit (e.g. for removing water, oil, etc., from air provided by the compressor). The compressor system, and in particular the compressor, may be mounted to the powertrain so as to be powered (e.g. mounted by means of gearing, belt arrangement, or the like). In particular, the compressor system may be mounted to an engine of the vehicle. The compressor system, and in some cases the compressor itself, may be configured to selectively control supply of compressed air to the vehicle systems (e.g. to the service reservoir). For example, the compressor system may comprise one or more controllable valves, operable to activate or deactivate supply of compressed air to the service reservoir. In some examples, the valves may be configured to activate/deactivate as so permit or inhibit compression. The valves may include unloader valves. The valves may be provided with the compressor and/or the air processor unit.

In other similar words, the compressor system may be switchable between an operational state and a non-operational state. In the operational state, the compressor system may be configured to provide, or be able to provide, compressed air, e.g. to the at least one service reservoir, when operated or driven by the engine or motor. In the non-operational state, the compressor system may be configured to provide less or preferably no compressed air, e.g. to the at least one service reservoir, which may be the case even when the engine or motor is operating. In some examples, in the non- operational state, the compressor system may not be able to provide compressed air.

The compressor system may be configured to permit control or selectively vary the load on the compressor system. Controlling or selectively vary the load of the compressor system may likewise vary the burden or load on the engine (or other powertrain components). The compressor system may be configured to receive one or more control signals in order to control operation thereof (e.g. control operation of one more or valves). The control signals may comprise pneumatic signals. The compressor system may be configured to receive pneumatic signals, or air pressure signals, and be operable based on the pressure of those signals (e.g. between an operational and non- operational state).

In some examples, the compressor system may be configured such that receipt of a first air pressure signal may cause the compressor system to enter a non-operational state (e.g. to stop supplying compressed air), while receipt of a second air pressure signal may cause the compressor system enter an operational state (e.g. to supply air). The first air pressure signal may be considered to be a high air pressure signal. The high pressure signal may be at, or around, an expected air pressure of the service reservoir when at rated pressure (e.g. rated pressure may indicate that the service reservoir is full). The second air pressure signal may be considered to be a high pressure signal. The low air pressure signal may be at or around atmospheric pressure.

In some examples, only the first and second air pressure signals may be used to control operably the compressor system. However, in other examples, a further control signal may be used to control operably the compressor system. The further control signal may be considered to be a feedback signal. The feedback signal may be representative of the air pressure in the service reservoir. The feedback signal may be a pneumatic signal. The feedback signal may be used cumulatively with the first and/or second air pressure signal in order to operatively control the compressor system. In similar words, the feedback signal may be combined with either the first or second pressure signal in order to operatively control the compressor system.

In such examples, the compressor system may be configured such that receipt of a low air pressure signal may cause the compressor system to supply compressed air when the feedback signal is also below a pressure threshold (e.g. only supply air when the feedback signal is also below a pressure threshold). Where the feedback signal is above a pressure threshold, then the compressor system may be configured stop supplying air (e.g. irrespective of the first or second signal). Further, the compressor system may be configured such that receipt of a high air pressure signal may cause the compressor system to stop supplying air, irrespective of the feedback signal. In some regards, the compressor system may be considered to operate an "OR" logic response with input (i) first or second air pressure signals and (ii) feedback signal. In such cases, a low pressure signal at the compressor system promoting an operational state may only be apparent when both the feedback signal is low, and the low air pressure signal is being communicated to compressor system.

The system may further comprise a controller configured to operatively control the system (e.g. the compressor system, and optionally a logic response). The controller may be configured to control the compressor system between the operational state and non-operational state.

The controller may be configured to observe particular driving conditions of the vehicle. The driving conditions observed by the controller may relate to engine usage, fuel usage of the vehicle, and in particular low fuel usage conditions. The driving conditions may relate to times where opportunistic use of kinetic energy may be used to operate the compressor system. The controller may be in communication with various vehicle sensors, configured to monitor one or more vehicle operating parameters. The controller may be in communication with sensors via a vehicle databus (e.g. CAN bus, or the like).

Upon observation of particular driving conditions, the controller may be configured to implement criteria or logic, specifying when to switch the compressor system from the operational state to the non-operational state and/or when to switch the compressor system from the non-operational state to the operational state.

It will be appreciated that specifying when to switch state may be subject to any override from a feedback signal. In other words, the controller may, based on observed driving conditions, specify that the compressor be switched to an operational state, but any feedback signal may indicate that the compressor need not be operative and supply air (e.g. when a service reservoir is full). In such cases, the controller can still be considered to switch to an "operational state" permitting operation, even if the compressor system remains inactive.

The criteria or logic may specify switching from the operational state to the non- operational state and/or switching from the non-operational state to the operational state when one or more ranges, values or criteria of at least one or more parameters of the vehicle are met.

The controller may be configured to communicate particular air pressure signals to the compressor system based on the observed driving conditions (e.g. observed vehicle parameters and/or driving conditions are met). For example, the controller may be configured to communicate the first air pressure signal during certain observed driving conditions, and the second air pressure signal during different driving conditions.

The one or more parameters of the vehicle may comprise one or more or each of: acceleration of the vehicle, accelerator pedal position, vehicle speed, rotational speed of the engine, air pressure in the vehicle braking system, air pressure in the vehicle suspension system, present operational state or condition of the compressor system.

One or more or each of these are parameters may be routinely measured and monitored, e.g. by engine control systems. As such, by basing the selective operation of the compressor system on such parameters, it may be possible to more readily retrofit, adapt or integrate the overall system, e.g. for use with existing vehicles.

The controller may be configured to switch the compressor system into the non- operational state, optionally for a determined or predetermined period of time such as an off-time, when the engine is fuelling and/or providing traction or motive power to the vehicle or the vehicle is accelerating, maintaining speed and/or is not coasting. The controller may be configured to switch the compressor system into the operational state when the vehicle is coasting, decelerating and/or the engine or motor is not fuelling and/or not providing traction or motive power to the vehicle. The controller may be configured to prioritize operation of the compressor system when the vehicle is coasting, decelerating and/or the engine is not fuelling and/or not providing traction or motive power to the vehicle.

By selectively prioritizing use of the compressor system in periods where the vehicle is coasting, decelerating and/or the engine is not fuelling and/or not providing traction or motive power to the vehicle, the additional fuel required by the engine in order to operate or drive compressor system may be reduced, which may thereby reduce the fuel consumption of the vehicle. In addition, the compressor may be operated more effectively, reducing degradation. The controller may be configured to determine if an accelerator pedal is depressed by more or less than an accelerator threshold amount. The controller may be configured to at least partially determine whether or not to switch the compressor system between the operational state and the non-operational state dependent on whether the accelerator pedal has been depressed by more or less than the accelerator threshold amount. For example, the controller may be configured to switch the compressor system to the operational state based at least partially on the determination that the accelerator pedal is being depressed by less than the accelerator threshold amount, and/or whether the pedal is being depressed at all. The controller may be configured to switch to the non-operational state based at least partially on the determination that the accelerator pedal is being depressed by more than a first accelerator threshold amount. The first accelerator threshold amount may be non-zero, e.g. between 1 % and 20%, such as between 2% and 10% and may be roughly 3%. The controller may be configured to switch to the operational state based at least partially on the determination that the accelerator pedal is being depressed by less than a second accelerator threshold amount. The second accelerator threshold amount may be nonzero, e.g. between 1 % and 20%, such as between 1 % and 10% and may be roughly 2%. Providing different thresholds for operational and non-operation states may help prevent switching between operation and non-operational when the accelerator pedal is depressed close to the thresholds.

The controller may be configured to determine if the vehicle speed is more or less than a speed threshold amount. The controller may be configured to at least partially determine whether or not to switch between the operational states dependent on whether the vehicle speed is more or less than the speed threshold amount. The speed threshold amount may be an absolute amount, in which case, determination of may be simply greater or lower than that absolute amount. However, the speed threshold amount may be range, in which case determination may be greater or lower than the range, or within the range.

For example, the controller may be configured to switch the compressor system into the operational state based at least partially on the determination that the vehicle speed is greater than a first particular speed (e.g. greater than 15 kp/h). The controller may be configured to switch the compressor system into the non-operational state based at least partially on the determination that the vehicle speed is less than a second particular speed (e.g. less than 13 kp/h). Again, providing different thresholds for operational and non-operation states may help prevent switching between operation and non-operational when the speed is close to the thresholds.

The controller may be configured to determine if the engine speed is more or less than an engine speed threshold amount. The controller may be configured to at least partially determine whether or not to switch the compressor system between the operational state and the non-operational state dependent on whether the engine speed is more or less than the engine speed threshold amount. For example, the controller may be configured to switch the compressor system into the non-operational state based at least partially on the determination that the engine speed is greater than the engine speed threshold amount (e.g. 500 rpm).

The controller may be configured to at least partially determine whether or not to switch the compressor system between the operational state and the non-operational state dependent on whether the system pressure is above or below a particular threshold) or greater than a running pressure). The "system pressure" may be considered to be the air pressure usable for a vehicle braking system, suspension system, or the like. For example, where the controller determines that the system pressure is below a particular system pressure threshold amount (e.g. indicative of low pressure for the brakes, suspension, or the like), then the controller may be configured to switch the compressor system to an operational state. In some cases, this may be irrespective of observed driving conditions. The system, and in particular the controller, may be configured to use one or more activation conditions to determine whether to switch the compressor system between operational and non-operational states. Each activation condition may be based on one or more different driving conditions or parameters. In some examples, the system, and in particular the controller, may be configured to switch the compressor system between operational state and non-operation state when at least one or a plurality of activation conditions have been met.

The system may further comprise a control reservoir. The control reservoir may be configured to store compressed air for subsequent supply as a control signal. The controller may be configured to provide compressed air from the control reservoir to the compressor system in order to switch the compressor system - if deemed appropriate - to a non-operational state. The system may be configured such that the control reservoir is supplied compressed air from a supply side of the compressor system, when the compressor system is an operational state. In some examples, the control reservoir may be configured to scavenge compressed air from the supply reservoir. A one-way valve may be provided between the compressor system and the control reservoir, to prevent air returning from the control reservoir to the supply side (or to the supply reservoir).

The system may comprise a first control valve configured to selectively communicate compressed air to the compressor system. The first control valve may be in communication with the control reservoir, and configured to selectively communicate compressed air from the control reservoir to the compressor system. The first control valve may be operatively controlled by the controller. The first control valve may comprise a solenoid.

The system may comprise a second control valve configured to selectively communicate air (e.g. atmospheric air) to the compressor system. The second control valve may be in communication with atmosphere, and configured to selectively communicate atmospheric air to the compressor system. The second control valve may be operatively controlled by the controller. The second control valve may comprise a solenoid.

The controller may be configured to pulse open and close the first control valve for a discrete period of time (e.g. around 10 seconds or less, 5 seconds or less, or around 1 second) in order to provide a first control signal to the compressor system. In doing so, and once closed, any compressed air of the control signal may be maintained within a supply line between the first control valve and the compressor system, without the need for the first control valve to remain open. Similarly, the controller may be configured to pulse open and close the second control valve for a discrete period of time (e.g. around 10 seconds or less, 5 seconds or less, or around 1 second) in order to provide a second control signal to the compressor system. The controller may be configured to delay operating the first control valve for a predetermined time after operating the second control valve. In some examples, the controller may be configured to delay operating the second control valve for a predetermined time after operating the first control valve.

The controller may comprise a processing unit such as a central processing unit (CPU). The controller may comprise an application specific integrated circuits, field programmable gate array, or the like. The controller may be or comprise or be comprised in an engine controller or a vehicle system controller. The controller may comprise or be configured to access a memory and/or data storage. The controller may comprise or be configured to access a communications system, e.g. for communicating with one or more vehicle parameter sensors, e.g. in order to receive or determine the one or more parameters of the vehicle and/or to communicate with the compressor system in order to selectively control the compressor system.

In some examples, there is described a compressed air system for a passenger service vehicle; the system comprising:

at least one service reservoir for providing compressed air to a particular vehicle system;

a compressor system for supplying compressed air to the service reservoir; the compressor system being configured to be operable between an operational state and an non-operational state based on an air pressure signal received at the compressor system; and

a controller configured to observe particular driving conditions of the vehicle, and to communicate particular air pressure signals to the compressor system based on the observed driving conditions. In such examples, a first air pressure signal may cause the compressor to supply air, while a second air pressure signal may cause the compressor to stop supplying air.

In some examples, there is described a retro-fit compressed air system for a vehicle, such as a passenger service vehicle.

The system may comprise a controller configured to observe particular driving conditions of the vehicle, and to communicate particular air pressure signals to an installed compressor system based on the observed driving conditions; such an installed compressor system having been installed to supply compressed air to a service reservoir or vehicle system and being configured to be operable between an operational state and an non-operational state based on an air pressure signal received at the compressor system. The system may comprising one or more control valves, in communication with the controller, and operatively controllable to provide air pressure signals.

In some examples, there is described a passenger service vehicle, or other heavy duty vehicle, comprising a compressed air system, compressor system and/or controller as described above.

In some examples, there is described a method for controlling an air compressor system for vehicle, such as a passenger service vehicle. The method may comprise observing particular driving conditions of the vehicle. The method may comprise communicating particular air pressure signals to an installed compressor system based on the observed driving conditions. Such an installed compressor system may have been installed to supply compressed air to a service reservoir or vehicle system and may be configured to be operable between an operational state and a non-operational state based on an air pressure signal received at the compressor system.

The method may comprise operating any of the above features, as described. The method may comprise optimising performance of a compressor system so as to reduce fuel usage. The method may comprise optimising performance of a compressor system so as to increase lifespan.

In some examples, there is described a computer program product that when programmed into a suitable controller configures the controller to perform any methods disclosed herein. There may be provided a carrier medium, such as a physical or tangible and/or non-transient carrier medium, comprising the computer program product. The carrier medium may be a computer readable carrier medium.

The invention may include one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. As will be appreciated, features associated with particular recited embodiments relating to air compressor systems may be equally appropriate as features of embodiments relating specifically to methods of operation or use, and vice versa.

It will be appreciated that one or more embodiments/aspects may be useful in improving fuel efficiency, and in some cases reduce running costs, maintenance costs, and vehicle downtime. The above summary is intended to be merely exemplary and non-limiting.

Brief Description of the Figures A description is now given, by way of example only, with reference to the accompanying drawings, in which:-

Figures 1 and 2 show examples of passenger service vehicles; Figure 3 is a schematic of a compressed air system for the vehicle of Figures 1 and 2;

Figure 4 is a schematic of a compressed air system, similar to that in Figure 3, for the vehicle of Figures 1 and 2; Figure 5 shows logic used by a controller of Figures 3 and 4 for putting a compressor system in an operational state; and

Figure 6 shows logic used by a controller of Figure 3 and 4 for putting a compressor system in a non-operational state.

Description of Specific Embodiments

Figure 1 shows a perspective representation of a passenger service vehicle 100, which, in this example, is shown as a vehicle 100 having both a lower passenger deck 1 10 (lower deck) and an upper passenger deck 120 (upper deck). Such vehicles 100 are commonly referred to as twin-deck, or double-deck, vehicles 100, and comprise a plurality of passenger seats on each deck. Figure 2 shows a perspective representation of an alternative passenger service vehicle 200, having essentially only a single passenger deck 210 (albeit there may be provided a few passenger seats on lower sections of the vehicle also). The vehicle 200 shown in Figure 2 can be considered to be a coach-type vehicle, in which the passenger deck 210 may be elevated above a luggage locker area 205, or the like. In some examples of such vehicles, the passenger deck 210 may extend for substantially the length of the vehicle 200, and so above a driver's cab (as shown by the dashed lines 215). Other single deck vehicles 200 are also known.

The examples of passenger service vehicles 100, 200 shown in Figures 1 and 2 are conventional vehicles in which traction is provided by an internal combustion engine. However, it will also be appreciated that the vehicles 100, 200 may alternately be hybrid electric or electric powered vehicles, and may use different powertrains or "engines". While, for the purposes of the following description reference will be made to vehicles using an internal combustion engine, nevertheless a skilled reader will recognise that the invention need not be so limited. Further, while described in relation to passenger service vehicles and the particular driving conditions that are experienced by such vehicles, it will be appreciated that the aspects and features described below may, in some cases, be utilised by other vehicles that may be use compressed air systems, such as trucks.

Many passenger service vehicles comprise pneumatic vehicle systems (or so-called subsystems) that use compressed air to power certain vehicle components. Examples include air brake systems, or air suspension systems or the like. Each system uses compressed air that is provided by the vehicle, typically from a compressor system that has a compressor and air processing unit. The compressor will compress air supplied from atmosphere and the air processing unit will, amongst other functions, remove moisture, oil or the like, from compressed air before being supplied to vehicle systems. Such compressor systems can be driven from the powertrain via gearing or direct drive, or belt driven, or the like. Loads experienced by the compressor system are therefore communicated to the engine. As such, the performance of the compressor systems can impact the overall fuel efficiency of the vehicle. Optimising the performance of such compressor systems may assist with improving fuel efficiency of the vehicle. In addition, compressor systems may typically require maintenance or repair. If such systems fail then with the vehicle may be inoperable, resulting in the vehicle being out of service, which can be costly for vehicle operators. Therefore, ensuring the long lifespan of such compressor systems can be valuable.

Typically, compressor systems do not operate continuously, but rather they may use a pneumatic feedback input to determine the present state of charge of a service reservoir, or the pressure at the vehicle systems, such as the brake or suspension systems. In doing so, such compressors may be loaded and using engine power when the pressure in the service reservoir, or the like, drops below a particular threshold. Often unloader valves, or the like, at an air processing unit and/or at the compressor itself may be operatively closed in order to permit compression when compressed air is needed, and operatively opened to inhibit compression at other times (e.g. in the example of a reciprocating compressor systems), thus loading and unloading the engine accordingly. However, with many compressor systems the only consideration given regarding when to "switch on" or "switch off the compressor system is regards to the air pressure.

Figure 3 shows an example of a compressed air system 300 for providing compressed air to one or more particular vehicle systems 310 (not shown in detail for ease). For example, the vehicle systems 310 may include one or more braking systems, suspension systems, or the like. In this particular example, the compressed air system 300 shown in Figure 3 comprises a service reservoir 320 for providing compressed air to particular vehicle systems 310.

Here, the vehicle compressed air system 300 comprises a compressor system 330 for supplying compressed air to the vehicle systems 310 (e.g. to the service reservoir 320, and then to the vehicle systems 310). The compressor system 330 comprises at least one compressor 340 and at least one air processing unit 350 (e.g. for removing water, oil, etc., from air provided by the compressor 340).

In this example, and not shown for ease, the compressor system 330 - and in particular the compressor 340 - is mounted to the powertrain of the vehicle so as to be powered. The compressor system can be mounted by means of gearing, or belt arrangement, or the like, as will be appreciated. Here, the powertrain to which the compressor system 330 is mounted is the internal combustion engine of the vehicle 100, 200.

As will be further explained, the compressor system 330 - and in some cases the compressor itself 340 - is configured to selectively control supply of compressed air to the vehicle systems 310 (e.g. to the service reservoir 320) and is switchable between an operational state and a non-operational state. In the operational state, the compressor system 330 is configured to provide, or be able to provide, compressed air, e.g. to the at least one service reservoir 320, when operated or driven by the engine or motor. In the non-operational state, the compressor system 330 is configured to provide less or preferably no compressed air, e.g. to the at least one service reservoir 320, which may be the case even when the engine or motor is operating. In some examples, in the non-operational state, the compressor system 330 may not be able to provide compressed air.

The compressor system 330 here is configured to permit control or selective variation of the load at the compressor system 330. Controlling or selectively vary the load of the compressor system 330 may likewise vary the burden or load on the engine (or other powertrain components), as will be appreciated. To achieve this, the compressor system 330 is configured to receive one or more control signals in order to control operation thereof. In the following description, the control signals are described as pneumatic signals, but of course in other embodiments the compressor system 330 may be controllable using electric signals, or the like.

However, by using pneumatic control signal, or otherwise implementing the control reservoir 360 and control arrangement (e.g. control valves), aspects of the overall compressed air system 300 may be retro-fit to existing compressor systems 330 (e.g. those that have pneumatic feedback inputs). In doing so, the system 300 may be implemented with ease and/or with minimum cost using functionality of components (e.g. compressor systems) that are presently utilised with passenger service vehicles. Further, controlling the compressor system 330 using pneumatic signals obviates the need for complex electronics or control/data acquisition systems to be provided with the compressor 340 and/or air processing unit 350. As such, the costs of replacement and/or repair of the compressor system 330 may be minimised. Here, the compressed air system 300 further comprises at least one control reservoir 360, as will be further explained. The control reservoir 360 is supplied compressed air from a supply side of the compressor system 330, during an operational state. A one- way valve 365 is provided here between the compressor system 330 and the control reservoir 360, which prevents air returning from the control reservoir 360 to the supply side of the compressor system 330. A check valve, or the like, may be used. The system 300 further comprises a first control valve 370, in communication with the control reservoir 360, and configured to selectively communicate compressed air from the control reservoir 360 to the compressor system 330. The system 300 also comprises a second control valve 375, in communication with atmosphere (or equivalent), and configured to selectively communicate atmospherically-pressurised air to the compressor system 330.

Both the output from the first control valve 370 and the second control valve 375 are pneumatically connected to a pneumatic feedback input (e.g. signal port) of the compressor system 330, that may otherwise be intended to receive feedback pressure from the service reservoir 320, or the like (e.g. via the air processing unit 350) as to the present state of charge of the reservoir 320, or vehicle systems 310.

As such, the compressor system 330 is able to receive, as a control signal, a first air pressure signal when the first control valve is open, and the second control valve is closed, and a second air pressure signal when the second control valve is open and the first control valve is closed.

Here, the compressor system 330 is configured such that receipt of a first air pressure signal causes the compressor system 330 to be in a non-operational state, while receipt of a second air pressure signal causes the compressor system 330 to be in an operational state. The second air pressure signal may be considered to be a low air pressure signal received after the second control valve has been opened, while the first air pressure signal may be considered to be a high pressure signal, received after the first control valve has been opened.

In the example described, the system 300 further comprises a controller 380, comprising a processor 382 and memory 384 configured in a known manner. The controller 380 is configured to control the compressor system 330 between the operational state and the non-operational state, as will be explained. Here, the controller is in communication with, and is configured to selectively operate, the first and second control valves 370, 375. It will be appreciated that the controller 380 may be, or comprise, an engine controller or a vehicle system controller.

Here, the controller 380 is in communication with various vehicle sensors 410, 420, 430, configured to monitor one or more vehicle operating parameters. The controller may be in communication with sensors via a vehicle databus 440 (e.g. CAN bus, or the like). The controller 380 is configured to observe particular driving conditions of the vehicle, and in particular those that relate to slowing down or fuel usage of the vehicle, such as low fuel usage conditions. Examples of times when a vehicle may be in a low fuel usage state or slowing include coasting, coast-down, or braking. During such times, it may be preferential to operate the compressor system 330 and make use of the kinetic energy of the engine/vehicle, and thus harvest this energy. In doing so, the compressor system 330 can charge the service reservoir 320, while only using minimal fuel.

Put similarly, by selectively prioritizing use of the compressor system 330 in periods where the vehicle is coasting, decelerating and/or the engine is not fuelling and/or not providing traction or motive power to the vehicle, the additional fuel required by the engine in order to operate or drive compressor system 330 may be reduced, which may thereby reduce the fuel consumption of the vehicle.

In use, when the vehicle initially starts, in some examples the controller may be configured to operate the compressor system 330 to charge the service reservoir 320 and, in doing so, also the control reservoir 360. The control reservoir 360 may therefore be charged to what would be the typical system cut-out pressure (i.e. the pressure at which the compressor switches off). In any event, subsequently, and during normal operation, when the vehicle engine is using fuel or the like, the controller is configured to maintain closed the second control valve 375, but open the first control valve 370, which communicates a high pressure pneumatic signal to the compressor system 330. In doing so, the compressor system 330 is maintained in a non-operational state. This may be achieved through opening of unloader valves, or the like, at the compressor 340 and/or air processing unit 350.

Here, the controller 380 is configured to pulse open and close the first control valve 370 for a discrete period of time (e.g. in this example, around 1 second is used) in order to provide a first high-pressure control signal to the compressor system 330. In doing so, any compressed air may be maintained within a supply line between the first control valve 370 and the compressor system 330, without the need for the first control valve 370 to remain open. As such, use of the compressed air in the control reservoir 360 can be optimised.

During normal operation, when the vehicle engine is not using fuel, coasting, braking or the like, the controller 280 is configured to maintain closed the first control valve 370, but open the second control valve 375, which in turn communicates a low pressure pneumatic signal to the compressor system 330. In doing so, the compressor system 330 switches from a non-operational state to an operational state. Again, this may be achieved through closing unloader valves, or the like, at the compressor 340 and/or air processing unit 350. As above, the controller 380 is configured to pulse open and close the second control valve for a discrete period of time (e.g. again, around 1 second for this example) in order to provide a second control signal to the compressor system 330. In doing so, the pressure of the second control signal is maintained. In some examples, the controller 380 is configured to delay operating the first control valve for a predetermined time (e.g. 100 ms) after operating the second control valve, and vice versa. In doing so, this ensures that compressed air is not unnecessarily depleted from the control reservoir 360, again optimising use of air in the control reservoir 360 and ensuring that the compressor system 330 minimises any time in an operational state.

During the operational state, the compressor system 330 functions as normal to charge the service reservoir 320. Additionally, the control reservoir 360 can be charged. Of course, from time to time, the service reservoir 320 (or pressure within the vehicle systems) may become undesirably low, even though braking or coasting conditions may not be occurring. In those circumstances, the controller 380 may be configured to monitor the pressure and operate the first/second control valves 370, 375 accordingly, to ensure appropriate pressure is restored. While in some examples, only the first and second air pressure signals may be used to control operably the compressor system 330, in other examples, a further pneumatic control signal may be used to control operably the compressor system 330. The further control signal may be considered to be a feedback signal. The feedback signal may be representative of the air pressure in the service reservoir 320.

Consider now Figure 4, which is similar to that of the system shown in Figure 3, apart from the provision of a feedback circuit 500. Here, the feedback circuit is a pneumatic circuit, thus providing a pneumatic signal to the compressor 340. While shown here in communication with a signal port of the compressor 340, it will be appreciated that the feedback signal (and indeed first and/or second control signals) may be communicated to a signal port of the air processing unit 350.

During use, the feedback signal is representative of the pressure in the system reservoir 320. In some examples, the feedback signal directly relates to system pressure, whereas in other examples the feedback signal may be set low (e.g. latch to atmospheric) when the cut in pressure of the system is reached (i.e. the pressure at which the compressor system would typically begin to charge the system). This low pressure may be maintained as a feedback signal until a cut-out pressure is reached in the reservoir, at which time the feedback signal may latch to the high reservoir pressure.

In any event, here, the feedback signal is used cumulatively with the first or second air pressure signal in order to operatively control the compressor system 330. In similar words, the feedback signal may be combined with either the first or second pressure signal in order to operatively control the compressor system 330.

In such examples, when the compressor system 330 receives a low air pressure signal as a control signal (e.g. meaning that the vehicle is braking, or the like), then this may cause the compressor system 330 to switch to an operational state. However, the compressor 340 may activate only when the feedback signal is also below a pressure threshold (e.g. only supply air when the feedback signal is also below a pressure threshold, meaning that the service reservoir does indeed require charging). Where the feedback signal is above a pressure threshold, then - and because the second control valve is closed - the pressure observed at the compressor 340 will essentially be that of the feedback signal, causing the compressor system 300 to be maintained in a non- operational state.

In some regards, the compressor system may be considered to operate a "OR" logic response with input (i) first or second air pressure signals and (ii) feedback signal. In such cases, a low pressure signal at the compressor system 330 promoting an operational state may only be apparent to the compressor 330 when both the feedback signal is low, and the low air pressure signal is being communicated to compressor system.

In some examples, a one-way valve 510 may be provided at the feedback circuit to prevent compressed air travelling to the air processing unit 350 from the compressor 340, or control valves 370, 375. It will be appreciated however, that providing a pneumatic feedback signal, rather than an electronic signal, may obviate the need to complex electronics and also assist with retrofit of the system 300.

It will be appreciated that, as shown in Figures 3 and 4, that the controller 380 can be in communication with various vehicle sensors 410, 420, 430 for measuring a plurality of vehicle parameters. These may be usable to determine a suitable time to operate or not operate the compressor system 330. For example, such sensors may include an accelerator pedal position sensor, a vehicle speed sensor, a pressure sensor for measuring pressure in the service reservoir 320 and/or vehicle systems 310, a state sensor for monitoring the present operating state or condition of the compressor system 330, an engine speed sensor for measuring the revolutions per minute (RPM) of the engine, or the like.

The controller 380 is configured to switch the compressor system 330 between the operational state and the non-operational state based on the vehicle parameters determined using such vehicle sensors. Specifically, in an embodiment, the controller 380 determines if the compressor system 330 should be switched from the non- operational to the operational state based on vehicle parameters including the accelerator pedal position, vehicle speed, engine speed, the present state or condition of the compressor, the system pressure in the system reservoir 320, and the state of the first/second control valves 370, 375.

In some cases, some of these vehicle parameters can be determined by an accelerator pedal position sensor 610, a vehicle speed sensor 620, the compressor state sensor 630 (which may be a downstream pressure sensor), and a system pressure sensor 640, and engine speed sensor 650, and a control valve sensor 660. In other cases, the some of the vehicle parameters may be determined from values stored at the controller 380 based on known/expected states. So, in this example, the state of the compressor, for example, is determined not from a sensor, but rather from a register value 630a at the controller 380 indicating expected condition. Again, in such a way, the system 300 can be simplified. Consider now Figure 5, which shows one example of the logic used by the controller 380 to determine whether to provide a low pressure control signal to the compressor system 330, or not, using the second control valve 375. The controller 380 obtains the accelerator pedal position from the accelerator pedal position sensor 610, and determines if the accelerator pedal position is less than an associated threshold amount, which in this example is 2% depressed. The controller 380 also obtains the vehicle speed from the vehicle speed sensor 620. The controller 380 then determines if the vehicle speed is greater than an associated threshold amount, which in this example is 15 km/h. The controller 380 further obtains the present state or condition of the compressor system 330 from the compressor state sensor 630 or register 630a and determines whether the compressor 340 is active, or not active. The controller 380 also determines if the system pressure is lower than the lower limit (indicating that charging would be appropriate).

If the controller 380 determines that the accelerator pedal position is less than the associated threshold amount, the vehicle speed is greater than the associated threshold amount and that the compressor is presently inactive, then the controller 380 determines that a first activation condition has been met. Otherwise, the controller 380 determines that the first activation condition has not been met.

The first activation condition represents a determination of whether or not the engine is currently fuelling, i.e. operating to drive or provide traction or motive power to the vehicle. For example, the accelerator pedal being depressed for less than a threshold amount (e.g. 2%) may be indicative of the vehicle coasting. The inventors have also advantageously found that placing the compressor system 330 into the operational state when the vehicle speed is very low can result in undesirable short charging periods and rapid switching of the compressor system 330 between the operational and the non-operational state, particularly in passenger service vehicles that can often perform short accelerations and decelerations at low speeds between closely spaced stops in urban areas. However, since the determination of the vehicle speed being above threshold amount before switching the compressor system 330 into the operational state, as described above, are built into the logic test for the first activation condition, such unwanted rapid switching can be advantageously avoided. It is noted here, that the actual fuel usage of the vehicle need not be determined for the first activation condition to be met. This again simplifies the system 300.

For a second activation condition, the controller 380 determines the pressure of the service reservoir 320. If the pressure is below a predefine threshold (which may be vehicle specific), then the second activation condition is met.

The controller 380 determines if either the first or second activation conditions has been met and if so, operates the low pressure control signal valve 375 so as to put the compressor 330 into the operational state, as described above. Otherwise, the compressor 340 remains in the non-operational state.

Similar to Figure 5, an example of logic used by the controller 380 to activate the high pressure control signal (e.g. open the first control valve 370), and thus switch the compressor 380 from the operational state to the non-operational state is shown in Figure 6. Here, the controller 380 firstly receives an indication of the system pressure from the system pressure sensor 640, and determines whether this is above an upper limit threshold. Additionally, the controller 380 determines the engine speed from the engine speed sensor 650. Where the engine speed is determined to be above a particular threshold (e.g. 500 RPM), which indicates that the vehicle is in a running phase, and the pressure in the system pressure is greater that an upper pressure limit (which can be vehicle dependent), then the controller 380 considers a first activation condition to have been met. On that merit alone, and provided the second control valve 375 is closed, the controller 380 is configured to open the first control valve 370 (in the pulsed manner described above). In doing so, the compressor 330 is switch to or maintained in a non-operational state.

However, where the pressure is the system 320 is determined, from the system pressure sensor 640, to be lower than the upper limit, but greater than a running pressure threshold (a threshold of pressure in the system, which can be set somewhere between the lower limit and upper limit) and the engine speed is determined to be above a particular threshold (e.g. 500 rpm), then the controller 380 uses this determination together with the either an accelerator pedal position being greater than a particular threshold (e.g. 3%) or vehicle speed being lower than a particular threshold (e.g. 13 kp/h) to provide a second and third activation condition respectively, provided the compressor system is also determined to in an operative mode.

If either of those activation conditions have been met, then the controller 380 is configured to open the first control valve 370 (in the pulsed manner described above) provided the second control valve 375 is determined to be closed. By permitting activation of the high pressure signal at low speed (provided sufficient running pressure exists), the system avoids switching on/off the compressor system during stop start conditions, that may be typical when operating a passenger service vehicle route. It will also be appreciated that using an accelerator pedal threshold amount and vehicle speed amount that differs slightly between open and closed logic, also prevents the system from undesirably toggling operational/and non-operational states, when the vehicle is being used close to those conditions.

For normal urban usage, representative of a passenger service vehicle usage, improved fuel usage can be obtained using the system and methods described above.

It will be appreciated that any of the aforementioned systems, valves, sensors or the like may have other functions in addition to the mentioned functions, and that these functions may be performed by the same systems/valves/sensors. Additionally, whilst the above examples have been described in relation to being particularly suitable passenger service vehicles as shown in Figures 1 and 2, or the like, it will be appreciated that certain aspects described may also be beneficially applied to other vehicles, such as boats, heavy duty vehicles including trucks, or the like (but being particularly suited to passenger service vehicles).

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAIMS:

1. A compressed air system for a vehicle; the system comprising:

a compressor system for supplying compressed air to the service reservoir; the compressor system being configured to be operable between an operational state and an non-operational state based on air pressure control signals received at the compressor system; and

a controller configured to observe particular driving conditions of the vehicle, and to communicate particular air pressure control signals to the compressor system based on the observed driving conditions.

2. The system according to claim 1 , wherein the controller is configured to communicate a first air pressure control signal during certain observed driving conditions and a second air pressure control signal during different driving conditions.

3. The system accordingly to claim 2, wherein the controller is configured to communicate the first air pressure signal to the compressor system so as to be in a non-operational state and the second air pressure signal to the compressor system so as to be in an operational state.

4. The system according to claim 2 or 3 wherein the first air pressure signal is a high air pressure signal at, or around, an particular air pressure of the service reservoir when partially or fully charged, and the second air pressure signal is a low pressure signal at, or around, atmospheric pressure.

5. The system according to any of the claims 1 to 4, wherein the compressor system is configured additionally to use a feedback signal to control operably the compressor system, the feedback signal being an air pressure signal representative of the air pressure in the service reservoir.

6. The system according to claim 5, wherein the feedback signal is used cumulatively with the air pressure control signals communicated by the controller in order to operatively control the compressor system.

7. The system according to any preceding claim, wherein the controller is configured observe driving conditions so as to prioritize operation of the compressor system when the vehicle is coasting, decelerating and/or the engine is not fuelling and/or not providing traction or motive power to the vehicle.

8. The system according to any preceding claim, wherein the controller is configured to use one or more parameters of the vehicle in order to observe particular driving conditions.

9. The system according to claim 8, wherein the controller is configured to determine if an accelerator pedal is depressed by more or less than an accelerator threshold amount in order to observe particular driving conditions.

10. The system according to claim 9, wherein the controller is configured to switch to the non-operational state based at least partially on the determination that the accelerator pedal is being depressed by more than a first accelerator threshold amount, and the controller is configured to switch to the operational state based at least partially on the determination that the accelerator pedal is being depressed by less than a second accelerator threshold amount, the first and second threshold amounts being different.

1 1. The system according to claim 8, 9 or 10, wherein the controller is configured to at least partially determine whether or not to switch between the operational states dependent on whether the vehicle speed is more or less than a speed threshold amount.

12. The system according to claim 1 1 , wherein the controller is configured to switch the compressor system into the operational state based at least partially on the determination that the vehicle speed is greater than a first particular speed threshold and configured to switch the compressor system into the non-operational state based at least partially on the determination that the vehicle speed is less than a second particular speed threshold, wherein the first and second thresholds are different.

13. The system according to any of the claims 8 to 12, wherein the controller is configured to use a plurality of activation conditions to determine whether to switch the compressor system between operational and non-operational states, each activation condition being based on one or more different parameters.

14. The system according to claim 13, wherein the controller is configured to switch the compressor system between operational state and non-operation state when at least one of the plurality of activation conditions has been determined to have been met.

15. The system according to any preceding claim further comprising a control reservoir configured to store compressed air for subsequent supply as an air pressure control signal to operatively control the compressor system.

16. The system according to claim 15, wherein the controller is configured to provide compressed air from the control reservoir to the compressor system in order to switch the compressor system to a non-operational state.

17. The system according to claim 15 or 16, wherein the system is configured such that the control reservoir is supplied compressed air from a supply side of the compressor system, when the compressor system is an operational state.

18. The system according to claim 15, 16 or 17 further comprising a first control valve, in communication with the control reservoir, and configured to selectively communicate compressed air from the control reservoir to the compressor system, the first control valve being operatively controlled by the controller.

19. The system according to claim 18 further comprising a second control valve, in communication with atmospherically-pressurised air, and configured to selectively communicate atmospherically-pressurised air to the compressor system, the second control valve being operatively controlled by the controller.

20. The system according to claim 19, wherein the controller is configured to pulse open and close the first and/or second control valve for a discrete period of time in order to provide a first/second control signal to the compressor system.

21. The system according to claim 20, wherein the controller is configured to delay operating the first control valve for a predetermined time after operating the second control valve, and vice versa.

22. A compressed air system for a vehicle, such as a passenger service vehicle, the system comprising:

a controller configured to observe particular driving conditions of the vehicle, and to communicate particular air pressure signals to an installed compressor system based on the observed driving conditions; such an installed compressor system having been installed to supply compressed air to a service reservoir or vehicle system and being configured to be operable between an operational state and an non-operational state based on air pressure control signals received at the compressor system.

23. The system according to claim 22, further comprising one or more control valves, in communication with the controller, and operatively controllable to provide air pressure signals.

24. The system according to claim 23, further comprising a control reservoir for storing compressed air to be used as a control signal.

25. The system according to any of the claims 22 to 24, wherein the system is configured to be retrofit to an existing compressor system of a vehicle.

26. A passenger service vehicle comprising a system according to any of the claims 1 to 25.

27. A method for controlling an air compressor system of a vehicle comprising: observing particular driving conditions of the vehicle; and

communicating particular air pressure control signals to an installed compressor system based on the observed driving conditions, such an installed compressor system having been installed to supply compressed air to a service reservoir or vehicle system and configured to be operable between an operational state and a non-operational state based on air pressure control signals received at the compressor system.

28. A computer program product configured to perform the method of claim 27.