WO2023066912A1

WO2023066912A1 - Control strategy to reduce air suspension venting noise

Info

Publication number: WO2023066912A1
Application number: PCT/EP2022/078937
Authority: WO
Inventors: Jake ANDREWS
Original assignee: Jaguar Land Rover Limited
Priority date: 2021-10-21
Filing date: 2022-10-18
Publication date: 2023-04-27
Also published as: GB202115073D0; GB2612071A; GB2612071B

Abstract

Aspects of the present invention relate to a control system (100) for use with a compressed air system having a first volume for storing compressed air and a second volume for storing compressed air and selectively connected to the first volume. The control system comprises one or more controller (110) and an output means (120) arranged to transmit control signals (125) to the compressed air system. The one or more controller (110) is arranged to determine a trigger event for decompression of the first volume, control, via the output means (120), the compressed air system to vent compressed air from the first volume to the second volume in dependence on the trigger event, and control, via the output means (120), the compressed air system to vent compressed air from the first volume to an external environment after venting compressed air from the first volume to the second volume.

Description

CONTROL STRATEGY TO REDUCE AIR SUSPENSION VENTING NOISE

TECHNICAL FIELD

The present disclosure relates to a control strategy to reduce air suspension venting noise. Aspects of the invention relate to a control system, a system for venting compressed air, a vehicle, a method for venting compressed air and a computer readable storage medium having stored thereon computer-readable instructions which are arranged to implement the method.

BACKGROUND

It is known to provide air suspension systems in vehicles for maintaining and controlling ride height, and to dampen movements of the vehicle, particularly to reduce user perception of uneven road surfaces and to improve user comfort. Vehicle air suspension systems are known to include one or more air springs, which when installed around a vehicle and filled with compressed air, serve to adjust a vehicle ride height and to mitigate unwanted movement of the vehicle cabin caused by travelling over uneven surfaces. The air springs may be filled with compressed air to varying pressures to change a vehicle ride height or to adjust the vehicle response to travel over an uneven surface.

The suspension systems typically comprise one or more air springs, a gallery for supplying compressed air to the air springs, a compressor for compressing air to supply to the gallery, and an exhaust for removing compressed air from the suspension system. The gallery may comprise a volume connecting the compressor to the one or more air springs and the exhaust via one or more valves which control the passage of compressed air. The gallery may also connect the exhaust and compressor to other components, such as a compressed air reservoir. The gallery may also be known as a compressed air gallery, a common gallery or a central gallery.

In certain situations, the suspension system, and in particular the gallery, may be required to decompress by removing compressed air from the suspension system or the gallery, such that the suspension system or the gallery contains air at approximately atmospheric pressure. This is usually achieved by opening the exhaust to vent compressed air from the system. As the gallery typically contains compressed air at pressures exceeding atmospheric pressure, opening the exhaust valve releases the compressed air to the external environment.

The exhaust enables high pressure compressed air from the gallery to exit the suspension system into the external environment via the exhaust. In certain vehicles, due to a high pressure differential between the gallery and the external environment, which is typically at atmospheric pressure, the release of compressed air from the gallery via the exhaust can be noisy both internally and externally to the vehicle, and result in noticeable and unwanted discomfort for a user of the vehicle and nearby persons.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a control system, a system for venting compressed air, a vehicle, a method for venting compressed air and a computer readable storage medium having stored thereon computer-readable instructions which are arranged to implement the method as claimed in the appended claims.

According to an aspect of the present invention there is provided a control system for use with a compressed air system having a first volume for storing compressed air and a second volume for storing compressed air and selectively connected to the first volume, the control system comprising one or more controller and an output means arranged to transmit control signals to the compressed air system, wherein the one or more controller is arranged to: determine a trigger event for decompression of the first volume; control, via the output means, the compressed air system to vent compressed air from the first volume to the second volume in dependence on the trigger event; and control, via the output means, the compressed air system to vent compressed air from the first volume to an external environment after venting compressed air from the first volume to the second volume.

In certain embodiments, the first volume is configured to be filled with compressed air at a first pressure and the second volume is configured to be filled with compressed air at a second pressure. Advantageously, by venting compressed air to the second volume before venting compressed air to the external environment, a pressure differential between the first volume and the external environment is reduced. Consequently, a noise associated with venting compressed air from the first volume through an exhaust is reduced.

In certain embodiments, the first and second pressures are greater than an air pressure of the external environment.

In certain embodiments, the first pressure is up to approximately 18 bar and the second pressure is between approximately 6 bar and 8 bar.

In certain embodiments, a trigger event for decompression of the first volume is an event indicative of a reduction requirement for the air pressure of the first volume.

According to another aspect of the invention, there is provided a system for compressed air venting of a vehicle, the system comprising: a first volume for storing compressed air; an exhaust valve for selectively venting compressed air from the first volume to an external environment; a second volume for storing compressed air; a connection means configured to selectively connect the second volume to the first volume; and control means configured to: determine a trigger event for decompression of the first volume; control the connection means to vent compressed air from the first volume to the second volume in dependence on the trigger event; and control the exhaust valve to vent compressed air from the first volume to the external environment after venting compressed air from the first volume to the second volume

In certain embodiments, the system is an air suspension system comprising a compressed air gallery and front and rear air springs, wherein the first volume comprises the compressed air gallery, and wherein the second volume comprises front and rear air springs.

In certain embodiments, the compressed air gallery is configured to selectively provide compressed air to the front and rear air springs.

In certain embodiments, the connection means comprises at least one valve operable to open and close a connection between the first volume and the second volume to allow or prevent compressed air to move between the first volume and the second volume.

In certain embodiments, the first pressure is approximately 18 bar and the second pressure is between approximately 6 bar and 8 bar.

In an embodiment, in use the first volume stores compressed air at a first pressure and the second volume stores compressed air at a second pressure.

In an embodiment, the first pressure is greater than the second pressure.

In certain embodiments, the first pressure is greater than or equal to the second pressure.

In an embodiment, the first volume comprises a compressed air gallery of a vehicle, and the second volume comprises an air suspension spring of the vehicle; and the compressed air gallery is configured to transfer compressed air to the air suspension spring.

In an embodiment, the air suspension spring comprises at least one first air spring arranged to be provided at a first end of the vehicle in use and at least one second air spring arranged to be provided at a second end of the vehicle in use; and the connection means comprises a first valve for selectively connecting the at least one first air spring to the compressed air gallery and a second valve for selectively connecting the at least one second air spring to the compressed air gallery.

In an embodiment, in use the at least one first air spring stores compressed air at the second pressure and the at least one second air spring stores compressed air at a third pressure; and the second pressure is greater than the third pressure. In certain embodiments, the third pressure is between 4 and 10 bar.

In an embodiment, to control the connection means to vent compressed air from the first volume to the second volume, the control means is configured to sequentially: control the first valve to open to enable compressed air to move from the compressed air gallery to the at least one first air spring and control the first valve to close; and control the second valve to open to enable compressed air to move from the compressed air gallery to the at least one second air spring and control the second valve to close. Advantageously, venting of compressed air from the first volume to the at least one first air spring and then the at least one second air spring reduces a change in vehicle ride height associated with venting compressed air to the air springs. In particular, since the at least one first air spring is at a higher pressure than the at least one second air spring, venting is first performed with the air springs that have a smaller pressure differential with the first volume. Subsequently, when venting the first volume to the at least one second air spring, the pressure differential will be less than if the venting is first performed with the at least second air spring or if the venting to the first and second air springs is performed simultaneously, thus reducing a ride height change caused by the at least one second air spring.

In an embodiment, the control means is configured to control the first valve and the second valve to respectively open for a first and a second predetermined time.

In certain embodiments, the first and second predetermined times are 150 milliseconds. In other embodiments, the first and second predetermined times are up to 3 seconds. In certain embodiments, the first and second predetermined times are based on a ratio of volume and pressure between the first volume and the second volume.

In an embodiment, controlling the exhaust valve to vent compressed air from the first volume to the external environment comprises controlling the exhaust valve to open for a predetermined time, until an air pressure in the first volume is substantially equal to an air pressure of the external environment or until the air pressure in the first volume is substantially equal to a predetermined pressure.

In an embodiment, the system comprises one or more air reservoirs selectively connected to the first volume and configured to store compressed air; an air compressor configured to compress air and to transfer the compressed air to the first volume; and a silencer arranged to reduce noise when compressed air is vented from the first volume via the exhaust valve.

In an embodiment, the trigger event comprises one or more of: receiving a signal indicative of a reduction requirement for the air pressure of the first volume; the control means identifying a request for a change in a ride height of the vehicle; and the control means determining that additional compressed air is to be added to the system.

In an embodiment, the control means is configured to: determine a current speed of the vehicle in dependence on the trigger event, determine if the current speed of the vehicle is below a pre-determined speed, and delay the venting to the second volume and the venting to the external environment until the current speed of the vehicle is determined to meet or exceed the pre-determined speed. Advantageously, user perception of the venting processed is reduced as a change in ride height associated with an air pressure of the second volume is less noticeable at vehicle speeds greater than the pre-determined speed.

In certain embodiments, the first pressure is approximately 18 bar and the second pressure is approximately 6 bar to 8 bar.

According to another aspect of the invention, there is provided a vehicle comprising the control system or the system.

According to another aspect of the invention, there is provided a method for compressed air venting of a vehicle, the method comprising: determining a trigger event for decompression of a first volume of the vehicle, the first volume being a container for storing compressed air; venting compressed air from the first volume to a second volume in dependence on the trigger event, the second volume configured for storing compressed air; and venting compressed air from the first volume to an external environment after venting compressed air from the first volume to the second volume.

In an embodiment, the first volume comprises a compressed air gallery of a vehicle and, in use, stores compressed air at a first pressure, and the second volume comprises an air suspension spring and, in use, stores compressed air at a second pressure lower than the first pressure; and the first and second pressures are greater than an external air pressure of the external environment.

In an embodiment, the air suspension spring comprises at least one first air spring and at least one second air spring; and the venting compressed air from the first volume to the second volume comprises sequentially: venting compressed air from the compressed air gallery to the at least one first air spring; and venting compressed air from the compressed air gallery to the at least one second air spring.

In an embodiment, venting compressed air from the compressed air gallery to the at least one first air spring comprises opening a first valve to allow compressed air to move from the compressed air gallery to the at least one first air spring for a first predetermined time and closing the first valve; and venting compressed air from the compressed air gallery to the at least one second air spring comprises opening a second valve to allow compressed air to move from the compressed air gallery to the at least one second air spring for a second predetermined time and closing the second valve.

In an embodiment, the method comprises determining a current speed of the vehicle in dependence on the trigger event; and determining if the current speed of the vehicle is below a pre-determined speed, delaying venting compressed air from the first volume to the second volume and the venting to the external environment until the current speed of the vehicle is determined to meet or exceed the pre-determined speed.

According to another aspect of the invention, there is provided a computer readable storage medium having stored thereon computer-readable instructions which are arranged to implement the method.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a block diagram representing a control system according to an embodiment of the invention;

Figure 2 shows a block diagram representing a system for compressed air venting of a vehicle according to an embodiment of the invention;

Figure 3 shows a diagram representing a system for compressed air venting of a vehicle according to an embodiment of the invention;

Figure 4 shows a first flow chart representing a method for venting compressed air of a vehicle according to an embodiment of the invention;

Figure 5 shows a second flow chart representing a method for venting compressed air of a vehicle according to an embodiment of the invention; and

Figure 6 shows a vehicle in accordance with an embodiment of the invention. DETAILED DESCRIPTION

A control system in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 1. The control system may be installed in a vehicle 600 shown in Figure 6. The vehicle 600 in the present embodiment is an automobile, such as a wheeled vehicle. Figure 1 shows a representation of the control system 100 in accordance with an embodiment of the invention.

The control system 100 of Figure 1 is shown to comprise a controller 105 comprising processing means 1 10, output means 120, input means 130 and memory means 140. The processing means 110, output means 120, input means 130 and memory means 140 are communicatively coupled with one another. Although Figure 1 shows the control system 100 comprising a single controller 105, it should be understood that the control system 100 may comprise a plurality of controllers each comprising processing means, output means, input means and memory means.

The processing means 110 may comprise processing means which may be one or more electronic processing devices or processors which operably execute computer-readable instructions. The control system 100 further comprises an input means 130 which may be an electrical input to receive one or more electrical signals 135. The input means 130 may be configured to receive a control signal indicative of a condition for decompression of a volume of a vehicle air suspension system. The control system 100 may comprise an output means 120 which may be an electrical output 120 for outputting one or more control signals 125 under control of the processing means 110. The one or more control signals output by the output means 120 may include control signals associated with controlling an internal valve or an exhaust valve to open or close. For example, the output means 120 may output a control signal 125 to a communications bus of a vehicle indicative of a determination that a valve should be opened to vent compressed air from an associated volume, or that a valve should be closed. One or more further control systems or processing units communicatively coupled to the communication bus of the vehicle may control various functions of the vehicle in response to receiving the output control signal 125 from the output means 120. The output means 120 may further comprise a display or audible output means for outputting a visual or audio output to a user.

The memory means 140 may be one or more memory devices. The memory means 140 is electrically coupled to the processing means 110. The memory means 140 is configured to store computer-readable instructions, and the processing means 110 are configured to access the memory means 140 and execute the instructions stored thereon.

The control system 100 is configured to receive decompression event data 135 at the input means 130 and determine that decompression of a volume of the vehicle is required. The control system 100 may then output a control signal 125 to control one or more valves to open or close. For example, the control system 100 may output a control signal 125 to at least one valve to vent compressed air from a first volume to a second volume, and subsequently may output a control signal to close the at least one valve. The control system 100 may output a control signal 125 to at least one exhaust valve to vent compressed air from the first volume to an external environment.

Figure 2 illustrates a system 200 for compressed air venting of a vehicle. Although not shown in Figure 2, the system 200 of Figure 2 may be installed in a vehicle in use. The system 200 of Figure 2 comprises a controller 210, a first volume 220, a second volume 230, a valve 240 and an exhaust valve 250. The system 200 of Figure 2 may comprise additional components not shown in Figure 2, as explained below.

The controller 210 of Figure 2 is configured to control each of the valve 240 and the exhaust valve 250 to open and close. The controller 210 of Figure 2 may comprise the control system 100 of Figure 1. For example, the controller 210 may be communicatively coupled with the valve 240 and the exhaust valve 250 such that the controller 210 is configured to transmit control signals to the valve 240 and the exhaust valve 250 to control the valve 240 and the exhaust valve 250 to open or close (the control signals being illustrated by dashed lines in Figure 2).

The controller 210 may further be configured to receive information or control signals from external sources or other parts of a vehicle, such as a vehicle communication bus, and make determinations to control the valve 240 and the exhaust valve 250 accordingly. The controller 210 is configured to determine a trigger condition indicative of a requirement for decompression of the first volume 220 or the second volume 230. In this case, decompression of a volume refers to venting compressed air from the volume so as to reduce an air pressure of the volume. For example, the controller 210 may determine a trigger condition for decompression of the first volume 220, and control the valve 240 to open to vent the first volume 220 to the second volume 230, and control the exhaust valve 250 to open to vent the first volume 220 to the external environment.

In some examples, the controller 210 may determine or receive information related to the vehicle including a current vehicle speed or a user input to control vehicle ride height, and may use this information when determining whether to decompress or vent the first volume 220. The controller 210 may be configured to control the valve 240 to open for a pre-determined period of time. In some cases, the pre-determined period of time is approximately 150 milliseconds. In another example, the pre-determined period of time may be up to several seconds, e.g., 3 seconds. In another example, the pre-determined period of time is calculated based on a ratio of volume and pressure between the first volume 220 and second volume 230. The pre-determined period of time may be adjusted to ensure as much pressure from the first volume 220 to the second volume 230 without being noticeable by an occupant of the vehicle or nearby persons. When the second volume comprises first and second air springs of a vehicle, and in particular front and rear air springs of a vehicle, the pre-determined period of time may also be based on achieving an equal ride height increase (due to additional air in the air springs) at both the front and rear air springs. The pre-determined period of time may therefore be calculable based on properties of a vehicle in use, including relative operating pressures and volumes of the first volume 220 and the second volume 230, and a function and a placement of the second volume 230 around the vehicle. The controller 210 may control the valve 240 to open for the pre-determined time and to close before controlling the exhaust valve 250 to open. The exhaust valve 250 may also be opened for a pre-determined time, or may be opened until an air pressure of the first volume 220 is substantially equivalent to an air pressure of the external environment. The system 200 may comprise means (not shown) for measuring an air pressure of the first volume 220, and may control to open and close the exhaust valve 250 and the valve 240 based on the measured air pressure of the first volume 220. The exhaust valve 250 may be controlled to open after the valve 240 has been opened and closed.

The first volume 220 and the second volume 230 are volumes configured to store compressed air. For example, the first volume 220 may be a compressed air gallery of a vehicle air suspension system. The compressed air gallery is a volume of the vehicle air suspension system which is provided to store compressed air and to channel compressed air between other parts of the vehicle air suspension system. For example, the compressed air gallery may be connected between a compressor, an exhaust, one or more compressed air reservoirs, and one or more air springs.

The second volume 230 of Figure 2 may in some examples be an air spring of a vehicle air suspension system, although the present disclosure is not limited thereto. For example, in another embodiment, the second volume 230 may be a volume provided to store compressed air received from the first volume 220 to provide a volume internal to the system 200 to which compressed air can be vented from the first volume 220. In other words, the second volume 230 may be a reservoir provided to receive compressed air from the first volume 220 when the first volume 220 is vented. The second volume 230 may store compressed air at a lower pressure than the air pressure of the first volume 220. For example, when the first volume 220 is a compressed air gallery, the first volume 220 may be configured to store compressed air at a pressure up to approximately 18 bar. When the second volume 230 is the one or more air springs, the second volume 230 may be configured to store compressed air at a pressure between approximately 6 and 8 bar. In another example, the second volume 230 may store compressed air at a pressure between 4 and 10 bar.

The first volume 220 and the second volume 230 are selectively connected by the valve 240. The valve 240 may comprise an electrically operated valve configured to open and close in dependence on a control signal from the controller 210. For example, the valve 240 may comprise a channel which is mechanically opened and closed by the valve 240 in dependence on the control signal. When the channel is open, compressed air is allowed to flow between the first volume 220 and the second volume 230. The first volume 220 is operable at air pressures up to a first air pressure, and the second volume 230 is operable at air pressures up to a second air pressure. In some examples, the first air pressure is greater than the second air pressure. In this case, as the first volume 220 operates at a higher air pressure than the second volume 230 in use, the direction of movement of the compressed air is from the first volume 220 to the second volume 230 due to a pressure differential between the first volume 220 and the second volume 230. The exhaust valve 250 is connected to the first volume 220 and configured to selectively connect the first volume 220 to an external environment in dependence on a control signal from the controller 210. That is, the exhaust valve 250 comprises means to connect the first volume 220 to the external environment such that when the exhaust valve 250 is open, compressed air is allowed to leave the first volume 220 into the external environment. The exhaust valve 250 may comprise an electrically operable valve which can open and close in dependence on a control signal. The external environment is an environment outside of the system 200 and typically outside of a vehicle 600. The external environment may have an air pressure substantially lower than the pressure of compressed air stored in the first volume 220 or the second volume 230. For example, the external environment may have an air pressure of approximately 1 bar.

As explained above, the controller 210 may control the valve 240 and the exhaust valve 250 to open sequentially. In other words, the controller 210 may determine to vent compressed air from the first volume 220 to the second volume 230 through the valve 240 before venting remaining compressed air of the first volume to the external environment through the exhaust valve 250. During venting of the first volume 220 to the second volume 230, an air pressure of the first volume 220 is reduced, and therefore a pressure differential between the first volume 220 and the external environment is reduced. Consequently, when the first volume is subsequently vented to the external environment, a noise associated with the venting through the exhaust valve 250 is reduced, and user comfort is improved. In the example discussed above, when the first volume 220 is a compressed air gallery operable at pressures up to approximately 18 bar and the second volume 230 is an air spring operable at between 4 and 6 bar, an air pressure of the first volume 220 may be reduced from approximately 18 bar to approximately 6 bar before the first volume 220 is vented to the external environment. Thus, a noise associated with the venting to the external environment may be reduced, as a pressure differential between the first volume 220 and the external environment is reduced. However, it should be understood that the operating pressures of the first volume 220 and the second volume 230 may have other values.

Figure 3 shows a diagram representing a system 300 for compressed air venting of a vehicle according to an embodiment of the invention. Although not shown in Figure 3, the system 300 of Figure 3 may be installed in a vehicle in use.

The system 300 of Figure 3 comprises a compressed air gallery 310, a front valve block 320 connected to front air springs 321 , a rear valve block 330 connected to rear air springs 331 , an exhaust valve 340, a silencer 341 , a compressor 350 and one or more compressed air reservoirs 360. The system 300 of Figure 3 may in some embodiments include further components or may omit some of the components shown. The system 300 of Figure 3 may be considered a particular implementation of the system 200 of Figure 2. Although not shown, the system 300 of Figure 3 may comprise a controller or be communicatively coupled with a controller. The controller may comprise the control system 100 of Figure 1 or the controller 210 of Figure 2.

In the example of Figure 3, the system 300 comprises a compressed air gallery 310. The compressed air gallery 310 may be considered a first volume. The compressed air gallery 310 is a volume configured to store compressed air at a first pressure. The compressed air gallery 310 is selectively coupled with the compressor 250, exhaust valve 340, front valve block 320 and rear valve block 330. The compressed air gallery 310 is configured to store compressed air and to provide compressed air to vehicle systems including the air spring blocks of Figure 3. In other words, the compressed air gallery 310 is a central volume used for delivery and control of compressed air to pneumatic vehicle systems including air suspension springs. The compressed air gallery 310 is configured to store compressed air at a first pressure, the first pressure being greater than an air pressure of an external environment. In certain examples, the first pressure may be up to 18 bar. The compressed air gallery 310 may be considered similar to the first volume 220 of Figure 2. The compressed air gallery 310 may have a volume of 0.5I.

The system 300 of Figure 3 includes a front valve block 320. The front valve block 320 may be positioned near a front end of a vehicle in use. For example, the front valve block 320 may be provided near an end of a vehicle proximal to a vehicle engine, and may be provided proximal to an underside of the vehicle. However, it should be understood that the position and function of the front valve block 320 is not limited thereto, and that the front valve block 320, and more specifically the front air springs 321 , are provided as an example of a second volume to which the first volume may be vented.

The front valve block 320 comprises one or more first valves 323. Although Figure 3 illustrates there being two first valves 323 in the front valve block 320, a different number of valves 323 may be present. The first valves 323 connect the compressed air gallery 310 to front air springs 321 via a first compressed air channel 322. The first valves 323 are configured to be operable to open and close so as to respectively allow or deny the passage of compressed air between the compressed air gallery 310 and the front air springs 321. The front air springs 321 are operable with compressed air at a second pressure. The second pressure may be lower than the first pressure of the compressed air gallery 310, such that when the first valves 323 are open, compressed air flows from the compressed air gallery 310 to the front air springs 321 as a result of the pressure being greater in the compressed air gallery 310 than in the front air springs 321 .

The front air springs 321 are configured to be filled with compressed air as part of a vehicle air suspension system. The front air springs 321 may therefore comprise a volume for storing compressed air at the second pressure. The front air springs 321 and the first compressed air channel 322 may be considered as a second volume, similar to the second volume 230 of Figure 2, or alternatively the front air springs 321 may be considered as a second volume alone. Figure 3 illustrates the system 300 as comprising two front air springs 321 , one to be provided on a left side of a vehicle and one to be provided on a right side of the vehicle. However, the system 300 is not limited thereto, and any number of front air springs 321 may be present. Each air spring may comprise a volume having a size of approximately 3I.

The system of Figure 3 further comprises the rear valve block 330. The rear valve block 330 is similar to the front valve block 320, but may be provided proximal to a rear end of a vehicle in use. The rear valve block 330 may comprise one or more second valves 333 connecting the compressed air gallery 310 to one or more rear air springs 331 via a second compressed air channel 332. The rear valve block 330, the one or more second valves 333, the one or more rear air springs 331 and the second compressed air channel 332 may respectively be similar to the front valve block 320, the one or more first valves 323, the one or more front air springs 321 and the first compressed air channel 322, and therefore a detailed description of each is omitted. However, these parts should be considered similar to the corresponding parts of the front valve block 320 discussed above.

The rear air springs 331 may operate and be configured to store compressed air at the second pressure, the same as the front air springs. In some embodiments, the rear air springs 331 may operate at and be configured to store compressed air at a third pressure, different to the second pressure. The third pressure may be lower than the second pressure, or may be greater than the second pressure. The third pressure and the second pressure are both lower than the first pressure of the compressed air gallery 310, and greater than an air pressure of the external environment. In some examples, the first pressure is 18 bar, the second pressure is between 6 and 8 bar, and the third pressure is between 4 and 10 bar. As with the front valve block 320, when the second valves 333 are opened, compressed air can flow from the compressed air gallery 310 to the rear air springs 331 due to a pressure differential between the compressed air gallery 310 at the first pressure and the rear air springs 331 at the second pressure or the third pressure.

The rear valve block 330 of Figure 3 is connected to an compressed air reservoirs 360 by a reservoir valve 361. However, the compressed air reservoir 360 may alternatively be connected to a different part of the system 300, for example to the compressed air gallery 361 or the front valve block 320 by a different valve. The reservoir 360 is configured to store compressed air, and may be configured to store compressed air to be transferred to the air springs via the compressed air gallery 310. In certain embodiments, the reservoir 360 may have a volume of between 2 and 12 litres, and may store compressed air at the first pressure. In some examples, more than one reservoir 360 is provided. For example, the reservoir may comprise a first reservoir having a volume of approximately 2.7 litres and a second reservoir having a volume of approximately 9 litres. The volume of the reservoir 360 may depend on a number of factors including ride height lift distance and speed of ride height change for a particular vehicle, and may vary between different vehicles.

The rear valve block 330 of Figure 3 is also shown to comprise a pressure transducer 370. The pressure transducer 370 is configured to provide feedback to a control system (not shown) and is pneumatically connected to the compressed air gallery 310. For example, the pressure transducer 370 may measure the pressure of the compressed air gallery 310 and provide an analog or digital signal to the control system indicative of the pressure of the compressed air gallery 310.

The system 300 of Figure 3 further comprises an exhaust valve 340. The exhaust valve 340 is configured to selectively connect the compressed air gallery 310 to the external environment. The exhaust valve 340 is operable to open and close so as to respectively allow or deny the passage of compressed air from the compressed air gallery 310 to the external environment. In some examples, the exhaust valve 340 is connected to the external environment via a silencer 341 which is configured to decrease a noise associated with compressed air passing through the exhaust valve 340. The system 300 of Figure 3 further comprises a compressor 350. The compressor 350 is configured to intake air, to compress the intake air and to provide the compressed air to the compressed air gallery 310. The compressor 350 may be a compressor of any known type which is suitable for compressing air to add into the system 300. For example, the compressor 350 may comprise a fixed displacement compressor or a variable displacement compressor. The system 300 may further comprise an air dryer 352 configured to dry intake air, a motor 353 to drive the compressor 350, an air intake filter 351 to filter intake air to remove particulates from intake air, and a flow restriction 354 to control a flow rate of air from the compressor 350 into the compressed air gallery 310.

The system 300 of Figure 3 may be installed on a vehicle in use. In use, the compressed air gallery 310, the front air springs 321 and the rear air springs 331 may store compressed air. In certain situations, it may be necessary or desirable to remove compressed air from the system 300, or from parts of the system 300. For example, it may be necessary or desirable to remove compressed air from the compressed air gallery 310. Removing compressed air from a volume may be known as decompression of the volume.

Decompression of a part of the system 300 of Figure 3 may be performed as a result of identifying a trigger event for decompression. For example, the compressed air gallery 310 may be vented to remove compressed air from the compressed air gallery 310 and to thereby decompress the compressed air gallery 310. A trigger event for decompression may include a determination that new or more compressed air is to be added to the system 300. In this example, to optimally operate the compressor 350 to add compressed air to the compressed air gallery 310, it may be necessary or desirable to reduce the pressure of the compressed air gallery 310 prior to operating the compressor 350. For example, it may be desirable to reduce the pressure of the compressed air gallery 310 to near the air pressure of the external environment. In another example, a change in vehicle ride height may be a trigger event for decompression of the compressed air gallery 310. The change in vehicle ride height may be determined by an air suspension vehicle to accommodate a change in road surface, or may be requested by a user input.

The system 300 may comprise control means to control the system 300 in dependence on the trigger event for decompression. If a trigger event for decompression of the compressed air gallery 310 is determined, the system 300 may control to vent the compressed air gallery 310.

According to an embodiment of the invention, the compressed air gallery 310 may be vented to the front air springs 321 and/or the rear air springs 331 by operating the first valve 323 and/or the second valve 333 to open for a first pre-determined period of time. The first pre-determined period of time may be 150 milliseconds in some examples.

The first valve 323 and the second valve 333 may be operated to open and close sequentially. For example, in the case where the second pressure is greater than the third pressure, the first valve 323 may be operated before the second valve 333. The first valve 323 and the second valve 333 may be operated to each open for the same amount of time, or may be opened for different amounts of time. As the first pressure of the compressed air gallery 310 is greater than the second and third air pressures, the pressure of the compressed air gallery 310 is reduced by the venting to the front air springs 321 and the rear air springs 331 .

After venting the compressed air gallery 310 to the front air springs 321 and the rear air springs 331 and closing the first valve 323 and the second valve 333, the compressed air gallery 310 may be vented to the external environment by opening the exhaust valve 340 for a second pre-determined period of time. The second predetermined period of time may be approximately 150 milliseconds in some examples. However, as with the first pre-determined time discussed above, the second pre-determined time may alternatively be up to several seconds, and may be determined based on a number of factors including a ratio of pressure and volume between the compressed air gallery 310 and the rear air springs 331. The second pre-determined period of time may be based on a time necessary to reduce the pressure of the compressed air gallery to a pressure similar to the external air pressure, which may be calculated by the system 300. Alternatively or in addition, the system 300 may comprise means for measuring the pressure of the compressed air gallery 310, and may determine to open the first valve 323, the second valve 333, and the exhaust valve 340 based on a pressure of the compressed air gallery 310.

The system 300 of Figure 3 may therefore vent the compressed air gallery 310 to the front air springs 321 and/or the rear air springs 331 before venting the compressed air gallery 310 to the external environment. The pressure of the compressed air gallery 310 is reduced with each step of the venting process, and therefore a pressure differential between the compressed air gallery 310 and the external environment is reduced prior to venting the compressed air gallery 310 to the external environment. Advantageously, this reduces a noise associated with venting compressed air through the exhaust valve 340, both internally and externally to the vehicle.

Further, in the case where the front air springs 321 contain compressed air at a second pressure greater than a third pressure of compressed air contained in the rear air springs 331 , the system 300 may control to vent the compressed air gallery 310 to the front air springs 321 prior to venting the compressed air gallery 310 to the rear air springs 331. Due to the pressure differential between the compressed air gallery 310 and the front air springs 321 being less than a pressure differential between the compressed air gallery 310 and the rear air springs prior to venting, noise associated with venting and user perception of the venting is reduced when the compressed air gallery 310 is vented to the front air springs 321 before it is vented to the rear air springs 331 . For example, venting the compressed air gallery 310 to the air springs may result in a change in ride height of the vehicle due to an increase in air pressure in the air springs. This change in ride height may be reduced by venting to the front air springs 321 and the rear air springs 331 sequentially, due to the difference in pressure between the second pressure and the third pressure. That is, in some examples, the front air springs 321 may operate at a higher air pressure than the rear air springs 331 , or may be filled with compressed air at up to a higher pressure than the rear air springs 331. Therefore, there may be a smaller pressure differential between the compressed air gallery 310 and the front air springs 321 , and venting from the compressed air gallery 310 to the front air springs 321 results in a smaller change in ride height of the vehicle than venting from the compressed air gallery 310 to the rear air springs 331. After venting the compressed air gallery 310 to the front air springs 321 , a pressure of the compressed air gallery 310 is reduced, and therefore a pressure differential between the compressed air gallery 310 and the rear air springs 331 is reduced compared to prior the venting of the compressed air gallery 310 to the front air springs 321 . Therefore, venting the compressed air gallery 310 to the rear air springs 331 after venting to the front air springs 321 results in less noticeable noise and ride height change to vehicle passengers by more gradually reducing the air pressure of the compressed air gallery 310. It should be understood that the front air springs 321 may not always operate at a higher air pressure than the rear air springs 331 , and that a different order of venting operations may be used depending on relative air pressures of the compressed air gallery 310, the front air springs 321 and the rear air springs 331 .

Properties of the vehicle may also be taken into account when considering an order of venting the compressed air gallery 310. For example, the presence of an engine block or other component may dampen the effect of increasing the ride height when venting the compressed air gallery 310 to the front air springs 321 or the rear air springs 331 depending on relative positions of the air springs and the engine block. It should therefore be understood that the compressed air gallery 310 may be vented to one or more internal volumes of the system 300 in any order.

Although the system 300 has been described above with reference to venting to the front air springs 321 before the rear air springs 331 , the invention is not limited thereto. In another example, the compressed air gallery 310 is vented to the rear air springs 331 before it is vented to the front air springs 321. In yet another example, the compressed air gallery 310 is vented to both the front air springs 321 and the rear air springs 331 simultaneously. In another example, the compressed air gallery 310 is vented to only one of the front air springs 321 or the rear air springs 331 before the compressed air gallery 310 is vented to the external environment.

Although the system 300 has been described above with reference to the front air springs 321 and/or the rear air springs 331 as being a volume to which the compressed air gallery 310 is vented prior to the compressed air galley 310 being vented to the external environment, the invention is not limited thereto. In another example, the compressed air gallery 310 is vented to another volume for storing compressed air prior to being vented to the external environment.

Figure 4 illustrates a first flowchart representing a method for venting compressed air of a compressed air system according to an embodiment of the invention, where the compressed air system comprises a first volume for storing compressed air, a second volume for storing compressed air and selectively connected to the first volume, and an exhaust valve selectively connecting the first volume to an external environment. The method of Figure 4 may be performed by the control system 100 of Figure 1 , the system 200 of Figure 2, the system 300 of Figure 3 or the vehicle 600 of Figure 6.

In the method of Figure 4, at step 410 a trigger event is determined. The trigger event may be an event for decompression of a first volume. For example, the trigger event may be indicative of a situation in which decompression of the first volume is required. For example, the trigger event may include a reception of a control signal indicative of a requirement to decompress the first volume, an indication that a compressor is to be operated to add compressed air to a system, or a request for a change in a vehicle ride height due to a determination by an air suspension system or a user request.

At step 420 of Figure 4, the method comprises venting the first volume to the second volume in dependence on the determination of the trigger event. Venting the first volume to the second volume comprises opening the valve between the first volume and the second volume to allow compressed air to pass from the first volume to the second volume. The valve may be opened for a pre-determined period of time before being closed. The second volume may comprise a single volume, or may comprise more than one volume, such as comprising the front air springs 321 and the rear air springs 331 of Figure 3. Similarly, the valve may comprise one or more valves. Venting the first volume to the second volume may comprise multiple venting steps, such as discussed above in respect of the front air springs 321 and the rear air springs 331 of Figure 3.

At step 430 of Figure 4, the method comprises venting the first volume to the external environment. Venting the first volume to the external environment may comprise opening the exhaust valve to connect the first volume to the external environment. The exhaust valve may be opened for a second pre-determined time.

The process of venting the system described above may optionally be performed in dependence of a vehicle speed or performed differently depending on a type of the trigger event. For example, if a current vehicle speed is below a pre-determined vehicle speed, the system may determine to vent the first volume directly to the external environment without first venting to the second volume. Alternatively, the venting of the first volume to the second volume and to the external environment may be delayed until the vehicle speed exceeds the pre-determined vehicle speed. Advantageously, a change in ride height associated with venting to vehicle air springs such as the front air springs 321 of Figure 3 may be less noticeable at greater vehicle speeds, and thus by considering a predetermined vehicle speed as a threshold speed for performing the venting of the compressed air gallery 310 to the vehicle air springs, or the venting of the first volume to the second volume, user comfort may be further increased and perception of the venting process may be reduced. In another example, if the trigger condition comprises a user request for a change in a ride height of the vehicle, the first volume may be vented directly to the external environment omitting the step of venting the first volume to the second volume in order to more quickly change the vehicle ride height.

Figure 5 illustrates a second flowchart representing a method for venting compressed air of a compressed air system according to an embodiment of the invention, where the compressed air system comprises a first volume for storing compressed air, a second volume for storing compressed air and selectively connected to the first volume, and an exhaust valve selectively connecting the first volume to an external environment. The method of Figure 5 may be performed by the control system 100 of Figure 1 , the system 200 of Figure 2, the system 300 of Figure 3 or the vehicle 600 of Figure 6.

At step 510, a trigger event is determined. Step 510 corresponds to step 410 of Figure 4 and so a description thereof will not be repeated. At step 520, it is determined whether a current vehicle speed is greater than a pre-determined vehicle speed. The current vehicle speed may be a speed at which a vehicle is currently travelling, and may be measured by a system of the vehicle or by an external system. The pre-determined vehicle speed may be a threshold speed below which venting from the first volume to the second volume is perceptible by a user more than a perception threshold, for example based on a change in ride height of the vehicle when the second volume is one or more air springs. The pre-determined vehicle speed may be 10kmph in some examples. In another example, the pre-determined vehicle speed may be up to 20kmph. The pre-determined vehicle speed may be determined based on a change in ride height associated with venting to the second volume, for example when the second volume comprises vehicle air springs. The change in ride height associated with the venting to the second volume may be based on a ratio of pressure and volume between the first volume and the second volume, and therefore may vary between vehicles. However, the pre-determined vehicle speed may be calculated taking into consideration vehicle properties so as to ensure that the change in ride height associated with the venting is not noticeable by a vehicle occupant. For example, a higher pre-determined vehicle speed may be determined for a vehicle having a large ride height change associated with venting from the first volume to the second volume, for example when the vehicle includes a large or high pressure first volume.

If the current vehicle speed is determined at step 520 to be greater than the pre-determined vehicle speed, the method proceeds to steps 550 and 560, in which the first volume is vented to the second volume and subsequently to the external environment. Steps 550 and 560 correspond to steps 420 and 430 of Figure 4, and a detailed description thereof is omitted.

If the current vehicle speed is determined at step 520 to not exceed the pre-determined vehicle speed, the method proceeds to step 530. At step 530, it is determined whether the trigger event for decompression of the first volume corresponds to a particular type of trigger condition. For example, the particular type of trigger condition may comprise a user request for a change in ride height of the vehicle. If the trigger event for decompression of the first volume is not determined to correspond to the particular type of trigger condition, the method proceeds to step 540.

At step 540, the method comprises delaying venting of the first volume. For example, the method may comprise delaying the venting of the first volume until the current vehicle speed is determined to be greater than the predetermined vehicle speed. Alternatively or in addition, the delay may be a pre-determined period of time. After the delay period of step 540 has expired, the method proceeds to steps 550 and 560, in which the first volume is sequentially vented to the second volume and the external environment as discussed above.

If the trigger event for decompression of the first volume is determined to correspond to the particular type of trigger condition, the method proceeds to step 560. As discussed above, at step 560, the first volume is vented to the external environment. In other words, if the trigger event for decompression of the first volume is determined to correspond to the particular type of trigger condition, the method comprises omitting the venting of the first volume to the second volume, and the first volume is instead vented directly to the external environment. Advantageously, particular trigger conditions related to certain functions of the vehicle such as a change in ride height may override the multi-step venting process of Figure 4, in order to vent the first volume as quickly as possible.

It should be understood that variations may be made to the method of Figure 5. In some examples, the delay of step 540 may be omitted for certain types of trigger condition. For example, if the trigger condition corresponds to a user input, the delay of step 540 may be omitted and the first volume may be immediately vented to the second volume at step 550. In another example, the type of trigger condition may be determined before the vehicle speed is determined at step 520. For example, it may be determined whether the trigger condition is a certain type of trigger condition, such as a control signal for vehicle ride height change. The determination of vehicle speed at step 520 may then be optional or dependent on the type of trigger condition. For example, if the trigger condition is the control signal for vehicle ride height change, the method may comprise immediately proceeding to step 550 or step 560, omitting a determination of vehicle speed. In another example, step 530 may comprise determining whether the trigger condition is a first, second or third type of trigger condition. In this example, if the trigger condition is the first type of trigger condition, the method may proceed to step 550, omitting the delay at step 540. If the trigger condition is the second type of trigger condition, the method may proceed to step 540, and delay the venting to the second volume in dependence on the vehicle speed. If the trigger condition is the third type of trigger condition, the method may proceed to step 560, and immediately vent the first volume to the external environment. It would be understood that various other modifications may be made to the method of Figure 5, and in particular certain operations may be omitted or performed at different times as explained above.

Figure 6 illustrates a vehicle 600 according to an embodiment of the present invention. The vehicle 600 comprises a control system 100 as illustrated in Figure 1 , a system 200 as illustrated in Figure 2, or a system 300 as illustrated in Figure 3. The vehicle 600 may perform the method of Figure 4 or Figure 5.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. It should be understood that any of the features described above with respect to Figures 1 to 6 may be taken in combination with features of any other Figure. In addition, features or method steps may be omitted.

Claims

1 . A control system for use with a compressed air system having a first volume for storing compressed air and a second volume for storing compressed air and selectively connected to the first volume, the control system comprising one or more controller and an output means arranged to transmit control signals to the compressed air system, wherein the one or more controller is arranged to: determine a trigger event for decompression of the first volume; control, via the output means, the compressed air system to vent compressed air from the first volume to the second volume in dependence on the trigger event; and control, via the output means, the compressed air system to vent compressed air from the first volume to an external environment after venting compressed air from the first volume to the second volume.

2. A system for compressed air venting of a vehicle, the system comprising: a first volume for storing compressed air; an exhaust valve for selectively venting compressed air from the first volume to an external environment; a second volume for storing compressed air; a connection means configured to selectively connect the second volume to the first volume; and control means configured to: determine a trigger event for decompression of the first volume; control the connection means to vent compressed air from the first volume to the second volume in dependence on the trigger event; and control the exhaust valve to vent compressed air from the first volume to the external environment after venting compressed air from the first volume to the second volume.

3. The system of claim 2, wherein in use, the first volume stores compressed air at a first pressure and the second volume stores compressed air at a second pressure; optionally the first pressure is greater than the second pressure.

4. The system of claim 2 or claim 3, wherein the first volume comprises a compressed air gallery of a vehicle, and the second volume comprises an air suspension spring of the vehicle; and wherein the compressed air gallery is configured to transfer compressed air to the air suspension spring.

5. The system of claim 4, wherein the air suspension spring comprises at least one first air spring arranged to be provided at a first end of the vehicle in use and at least one second air spring arranged to be provided at a second end of the vehicle in use; and wherein the connection means comprises a first valve for selectively connecting the at least one first air spring to the compressed air gallery and a second valve for selectively connecting the at least one second air spring to the compressed air gallery.

6. The system of claim 6, wherein in use the at least one first air spring stores compressed air at the second pressure and the at least one second air spring stores compressed air at a third pressure; and wherein the second pressure is greater than the third pressure.

7. The system of any of claims 5 to 6, wherein to control the connection means to vent compressed air from the first volume to the second volume, the control means is configured to sequentially: control the first valve to open to enable compressed air to move from the compressed air gallery to the at least one first air spring and control the first valve to close; and control the second valve to open to enable compressed air to move from the compressed air gallery to the at least one second air spring and control the second valve to close.

8. The system of claim 7, wherein the control means is configured to control the first valve and the second valve to respectively open for a first and a second predetermined time.

9. The system of any of claims 2 to 8, wherein controlling the exhaust valve to vent compressed air from the first volume to the external environment comprises controlling the exhaust valve to open for a predetermined time, until an air pressure in the first volume is substantially equal to an external air pressure of the external environment or until the air pressure in the first volume is substantially equal to a predetermined pressure.

10. The system of any of claims 2 to 9, comprising: one or more air reservoirs selectively connected to the first volume and configured to store compressed air; an air compressor configured to compress air and to transfer the compressed air to the first volume; and a silencer arranged to reduce noise when compressed air is vented from the first volume via the exhaust valve.

11 . The system of any of claims 2 to 10, wherein the trigger event comprises one or more of: receiving a signal indicative of a reduction requirement for the air pressure of the first volume; the control means identifying a request for a change in a ride height of the vehicle; and the control means determining that additional compressed air is to be added to the system.

12. The system of any of claims 2 to 11 , wherein the control means is configured to: determine a current speed of the vehicle in dependence on the trigger event, determine if the current speed of the vehicle is below a pre-determined speed, and delay the venting to the second volume and the venting to the external environment until the current speed of the vehicle is determined to meet or exceed the pre-determined speed.

13. A vehicle comprising a control system according to claim 1 or a system according to any one of claims 2 to 12.

14. A method for compressed air venting of a vehicle, the method comprising: determining a trigger event for decompression of a first volume of the vehicle, the first volume being a container for storing compressed air; venting compressed air from the first volume to a second volume in dependence on the trigger event, the second volume configured for storing compressed air; and venting compressed air from the first volume to an external environment after venting compressed air from the first volume to the second volume.

15. A computer readable storage medium having stored thereon computer-readable instructions which are arranged to implement a method according to claim 14.