Pneumatic system, vehicle with such a system, and a method for controlling such a system

Abstract

A pneumatic system comprises a compressor and a regenerative air dryer. The pneumatic system is switchable between (i) a loading mode in which the compressor is actuated and compressed air is driven through the dryer to one or more consumers and (ii) a non-loading mode in which the compressor output is fluidly connected to the atmosphere and the compressor is idle. The compressor output remains fluidly connected to the atmosphere when transitioning from the non-loading mode to the loading mode until the compressor completes a transition from idle to actuated.

Description

PNEUMATIC SYSTEMFIELD

[0001] Embodiments of the present disclosure relate generally to pneumatic systems, in particular pneumatic supply systems, especially for industrial or utility vehicles, such as tractors, other agricultural vehicles, construction vehicles and others.BACKGROUND

[0002] Vehicle air supply systems require air dryers to discharge humidity from the air before supplying it to consumers (i.e., on-board or external equipment requiring a pneumatic supply such as pneumatic actuators, pneumatic cylinders, pneumatic motors and reservoirs or accumulators for storing a pressurized air supply for such equipment). Damp air can cause corrosion in pipes and other components on the vehicle, so before supplying air to consumers (for example, for the vehicle's brake system) the air is usually guided through a dryer. When the air is passing through the dryer to dry the air, this mode of operation is known as a drying or loading mode.

[0003] Due to the restricted load capacity of dryers, a second operation mode, known as a regeneration mode, is required which involves passing air through the reservoir in an opposite direction and discharging it to the atmosphere to remove water deposited in, or on, the drying material of the dryer.

[0004] It is known to use double chamber dryers which comprise two separate dryer reservoirs, so that if one chamber is drying the air from the compressor in a loading mode, the other chamber can be operated in a regeneration mode. The shift between the two modes of each drying chamber is time-controlled, so that the dryer may continually be used to dry air.

[0005] Furthermore, Electrically Operated Air Dryers (EODs) are also known. These dryers only require one dryer portion and the shift between the two modes of operation, that isthe switch between the regeneration mode and the loading mode, is controlled electronically. This may be time-controlled by a control unit. For example, the two modes can be controlled by measuring the volume of air passing through the dryer by measuring the compressor time or measuring the pressure rise in the reservoirs (and knowing that a certain pressure rise requires a predetermined air volume). A percentage of the volume of air in the air supply system can be guided back for the regeneration. An example of a pneumatic supply system on a vehicle having an EOD is described in EP3127721B1 to ACO International GmbH.

[0006] It is known to place a compressor of a pneumatic supply system into an idle mode as part of the non-loading mode of the EOD to save energy.

[0007] For compressors that are permanently connected to a power source, such as an internal combustion engine, so that the compressor is always running when the engine is running, an idle mode is created by reducing the output of the compressor. There are many permanently connected compressor designs with an energy saving idle mode. For example, most two-cylinder compressors use the pressure in an energy saving pipe to open a valve between the two cylinders. Air is no longer compressed and output is instead only cycled between the two cylinders. In one-cylinder compressors, the pressure in an energy saving pipe may be used to open a valve, so that air is no longer compressed but is exhausted to atmosphere. Another possibility is a separate valve between a cylinder and the suction port. Pressure in an energy saving pipe opens this valve and air in the cylinder will flow back to suction port.

[0008] It also known to use compressors having a drive that can be switched on and off so that the compressor is not driven when in an idle mode. Examples include a compressor driven by an electric motor where the motor is stopped when the compressor is in an idle mode, a hydraulically driven compressor where the hydraulic motor is stopped when the compressor is in an idle mode, and a clutched compressor connected to any suitable power source, such as an internal combustion engine, an electric or hydraulic motor, or a hybrid drive train, in which drive to the compressor is switched off by disengaging the clutch when the compressor is in an idle mode. This type of arrangement will be referred to herein as "switchable drive compressor"

[0009] Switching the drive to the compressor off in an idle mode saves energy.However, if the timing of the idle state is simply linked to the non-loading mode of the EOD, the compressor can experience a high load during start up. The compressor and its drive have to be designed to tolerate these high loads.BRIEF SUMMARY

[0010] The scope of this disclosure is defined by the claims.

[0011] According to examples in accordance with this disclosure, there is provided a pneumatic system, comprising: a compressor having an idle mode in which the compressor is not driven and an actuated mode in which the compressor is driven; an electrically operated air dryer, EOD, having an input fluidly connectable to the compressor, a dryer unit, an output configured to be fluidly connected to at least one consumer, a discharge valve selectively operable to fluidly connect the EOD input to atmosphere; and a controller, wherein the controller is configured to switch the pneumatic system between (i) a loading mode in which the compressor is in actuated mode, the input to the EOD is not fluidly connected to atmosphere through the discharge valve, and compressed air from the compressor is driven through the EOD in a first direction to the at least one consumer and (ii) at least one nonloading mode in which the input to the EOD is fluidly connected to atmosphere by the discharge valve and the compressor is in idle mode, wherein the controller is configured to maintain the fluid connection of the input of the EOD to the atmosphere when transitioning from the at least one non-loading mode to the loading mode until the compressor completes a transition from idle mode to actuated mode.

[0012] By keeping the compressor vented to the atmosphere until the compressor has fully powered from idle mode to its actuated mode, the load on the compressor drive system is kept low during start up. Where the compressor is driven by an electric motor, this reduces start up currents and hence enables a lower specification compressor motor to be used (cable cross sections, fuse protection, maximum current provision, etc.). In the case of a compressor driven from a power source through a clutch, this enables the load on the clutch to be reduced and hence enabling a more compact design and / or longer service life.

[0013] The controller may also be configured to fluidly connect the input to the EOD to the atmosphere using the discharge valve for an initial period before starting a transition of the compressor from actuated mode to idle mode.

[0014] By venting the compressor to the atmosphere before switching to the idle state, it is ensured that any water present in the system is vented.

[0015] The EOD may comprise: a one-way output valve between an output of the dryer unit and the output of the EOD, the one-way output valve configured to allow air to pass only in the first direction from the dryer unit to the EOD output; a regeneration valve connected in parallel to the one-way output valve between the dryer unit output and the EOD output and selectively operable for bypassing the one-way output valve to allow air to flow in a second direction opposite to the first direction from the EOD output through the dryer unit; and a governor valve having an output port fluidly connected to a control pilot port of the discharge valve, the governor valve being selectively operable in a first configuration to fluidly connect the output port to the EOD output to actuate the discharge valve to fluidly connect the EOD input to atmosphere.

[0016] This is one example of the configuration of a regenerative, electrically operated dryer. The controller is for example configured to operate the governor valve to maintain the coupling of the compressor output to the atmosphere.

[0017] In a first set of examples, the compressor is driven by an electric motor and the controller comprises a motor controller for electronically controlling the electric motor.

[0018] In a second set of examples, the compressor is driven by a hydraulic motor and the controller comprises a hydraulic motor controller for electronically controlling the hydraulic motor.

[0019] In a further set of examples, the compressor is driven from a power source through a clutch controlled by the controller. The power source may be an internal combustion engine, and electric motor, a hydraulic motor, or a hybrid drive train. The clutch may have a pneumatic actuator, the pneumatic actuator being selectively fluidly connectable to a source ofpressurized fluid via an electronically controllable idle mode actuation valve. In embodiments, the idle mode actuation valve is selectively operative to fluidly connect the pneumatic clutch actuator to an output port of a governor valve of the EOD. In other embodiments, the idle mode actuation valve is selectively operative to fluidly connect the pneumatic clutch actuator to the output of the EOD.

[0020] In all examples, the at least one non-loading mode may include a holding mode and a regeneration mode in which the at least one consumer is fluidly connected to the output of the drying unit, and the controller may be configured to switch the pneumatic system between (i) the loading mode, (ii) the holding mode, and (iii) the regeneration mode.

[0021] This disclosure also provides a vehicle comprising the pneumatic system as set out above.

[0022] The at least one consumer for example comprises at least one selected from the following list: rear service brake; front service brake; park brake; trailer brake; tire pressure control system; cab air supply; dust discharge system.

[0023] The vehicle may comprise a vehicle, or a combination of a vehicle and an associated implement. The vehicle may be an agricultural vehicle. The associated implement may be an agricultural implement.

[0024] This disclosure also provides a method of controlling a pneumatic system comprising a compressor having an idle mode in which compressor is not driven and an actuated mode in which the compressor is driven and a regenerative electrically operated air dryer, EOD, wherein the method comprises: switching the pneumatic system between: (i) a loading mode in which the compressor is in the actuated mode and compressed air from the compressor is driven through the EOD in a first direction to the at least one consumer; and (ii) at least one non-loading mode in which an input to the EOD is fluidly connected to atmosphere by a discharge valve and the compressor is in the idle mode, wherein the method comprises: maintaining a fluid connection of the input to the EOD to atmosphere when transitioning from the at least one non-loading mode to the loading mode until the compressor completes a transition from idle mode to actuated mode.

[0025] The method may further comprise fluidly connecting the input to the EOD to atmosphere for an initial period before starting a transition of the compressor from actuated mode to idle mode.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] One or more embodiments of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] FIG. 1 shows a tractor, as one example of a vehicle that can make use of the pneumatic system of this disclosure;

[0028] FIG. 2 shows a circuit diagram of part of a pneumatic supply system for use on the vehicle of FIG. 1, the pneumatic supply system having an EOD;

[0029] FIG. 3 shows the EOD of FIG. 2 operating in a loading mode;

[0030] FIG. 4 shows the EOD of FIG. 2 operating in a non-loading holding mode;

[0031] FIG. 5 shows the EOD of FIG. 2 in an overpressure protection mode;

[0032] FIG. 6 shows the EOD of FIG. 2 operating in a regeneration mode;

[0033] FIG. 7 is a composite schematic drawing illustrating two examples of pneumatic circuit of this disclosure;

[0034] FIG. 8 illustrates method of controlling a pneumatic system such as the system of FIG. 7;

[0035] FIG. 9 illustrates a further example of pneumatic circuit of this disclosure; and

[0036] FIG. 10 illustrates a still further example of pneumatic circuit of this disclosure;DETAILED DESCRIPTION

[0037] The subject matter of this disclosure will be described with reference to the Figures.

[0038] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intendedfor purposes of illustration only and are not intended to limit the scope of the disclosure. These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0039] This disclosure relates to a pneumatic system which comprises a switchable drive compressor and a regenerative electrically operated air dryer, EOD. The pneumatic system is changeable between (i) a loading mode in which the input to the EOD is not fluidly connected to atmosphere, the compressor is in an actuated mode with drive to the compressor switched on and compressed air is driven through the dryer to one or more consumers and (ii) at least one non-loading mode in which the input to the EOD is fluidly connected to the atmosphere and the compressor is in an idle mode with drive to the compressor switched off. The input to the EOD (and hence the compressor output) remains fluidly connected to the atmosphere when transitioning from the non-loading mode to the loading mode until the compressor completes a transition from idle mode to actuated mode.

[0040] Before describing the concept of this disclosure, examples of the type of vehicle in which the pneumatic system may be used will be discussed, and the known operation of an EOD will be explained.

[0041] The pneumatic system of this disclosure may be applied to a vehicle alone (having pneumatically powered on-board equipment) or to a vehicle towing or otherwise associated with an implement. In the latter case, part of the pneumatic system may be in the main vehicle and part of the pneumatic system may be in the associated implement.

[0042] FIG. 1 shows an agricultural tractor 1, as one example of a vehicle that can make use of the pneumatic supply system of this disclosure. The tractor 1 is shown towing an agricultural implement in the form of a planter 2, as one example of an implement associated with a vehicle. The tractor is coupled to the planter by a hitch 3. The planter comprises a seed tank 4 and a control system 5 which regulates delivery of seed to a number of row units 7 mounted to a tool bar 6.

[0043] The pneumatic supply system of this disclosure is not limited to use on tractors or other agricultural vehicles or machines (such as combine harvesters, sprayers and the like) but can be adapted for use with any industrial or utility vehicle requiring a pneumatic air supply, including construction vehicles, trucks and lorries and others. Indeed, the pneumatic system of this disclosure can also be adapted for use in any pneumatic system, whether on a vehicle or not.

[0044] FIG. 2 shows a circuit diagram of a pneumatic supply system 9 having an EOD 100, for example for mounting on a vehicle 1 such as the tractor 1.

[0045] A compressor 10 supplies air to components on the vehicle via the EOD 100. The EOD is connected to various consumers (illustrated schematically at 30, 40, 50, 60) via a consumer branch 20 connected to an output of the EOD. In this example, the consumers 30, 40 are primary consumers and the consumers 50 and 60 are secondary consumers. Reservoirs 31, 41 are assigned to the primary consumers 30, 40 and are equipped with pressure sensors 32, 42 to measure the pressure of the compressed air in the consumer branches. Consumers 50 or 60 may also be equipped with respective reservoirs and / or pressure sensors. Generally, the system will try to maintain the reservoirs at a defined pressure level, for example in the range of 8.5 bar (850 kPa) to 12.5 bar (1259 kPa), to ensure that they can deliver the required air pressure when required.

[0046] The consumer branch 20 is connected with the various consumers through a multi-circuit protection valve system 21. The multi-circuit protection valve system can take various forms as are well known in the art and may be operative to balance the pressure required to be supplied to the primary set of consumers 30, 40 and the secondary consumers 50, 60 and / or to cut the supply to any consumer should a consumer develop a leak. In this way, the integrity of the supply to the remaining consumers is maintained. Furthermore, the multicircuit protection valve system 21 may be configured to ensure that the supply to the primary consumers is prioritized over the supply to secondary consumers, such as a tire pressure control system, TPCS, 61. Examples of multi-circuit protection valve systems are disclosed in GB1387892 to Robert Bosch GmbH and GB1563144A to WABCO Westinghouse GmbH.

[0047] By way of example, in tractors or trucks, primary consumers 30 and 40 may be parallel brake circuits for a dual-circuit service brake. Secondary consumers 50, 60 may be a parking brake, an air suspension of the cab and / or wheels, or the TPCS 61, for example.

[0048] Compressor 10 is equipped with idler means 11 to provide an idle mode in which the air flow is reduced to a rate of, for example, 15% of the maximum air delivery, which in a non-limiting example may be in the region of 400 to 1000 liters per minute.

[0049] The electrically operated air dryer (EOD) 100 comprises a dryer unit 101 comprising a cartridge filled with drying granules (desiccant), a discharge valve 102, a regeneration valve 103, a governor valve 104, and a one-way output check valve 105. The system has an electronic control unit 70, which may be a computer or CPU. For clarity reasons, the electric connections of valves 102, 103 and 104 to the control unit 70 are only indicated by the dashed arrows. The control unit is coupled to a display 71. The regeneration valve 103 is connected in parallel to the output check valve 105 between the output of the dryer unit 101 and the consumer branch / output of the EOD 100.

[0050] The granule cartridge extracts water from the air passing through it in a first direction from the compressor to the consumers.

[0051] With reference to FIGs. 3 to 6, standard operating modes of the pneumatic system are now explained:

[0052] FIG. 3 shows a loading or drying mode.

[0053] When air is required to be supplied to the consumer branch 20, air from compressor 10 flows to the consumer branch 20 in a first direction through dryer unit 101 and check valve 105 as shown by the dotted path LP. During loading, discharge valve 102 is in its closed position 102a biased by spring 102b, as shown in FIG. 3. The regeneration control valve 103 and governor valve 104 are also in their closed positions 103a and 104a biased by springs 103b and 104b. Air flow in an opposite direction, that is from the consumer branch 20 to compressor 10, is prohibited by check valve 105 and the closed regeneration valve 103.

[0054] FIG. 4 shows a non-loading, idle mode. This will also be referred to as a holding mode.

[0055] If the consumers are provided with sufficient air pressure, the pressure in the reservoirs 31, 42 is at a predetermined pressure in the range of 8.5 bar (850 kPa) to 12.5 bar (1259 kPa) in this non-limiting example. This pressure is measured by sensors 32, 42 in reservoirs 31, 41. If this pressure is exceeded because compressor 10 is still working, the control unit 70 switches the governor valve 104 from a closed position 104a (biased by spring 104b) to an open position 104c by energizing solenoid 104d to guide air along path IP1 from the consumer branch 20 through an output port of the governor valve to the compressor idler 11. The output port of the governor valve 104 is also connected to a pilot port 102d of the discharge valve 102 via path DPI so that when the governor valve is in the open position 104c, the discharge valve 102 is moved to its open position 102c for fluidly connecting the EOD inlet, and hence the compressor outlet, to the atmosphere. Thereby the remaining air flow from the compressor (which may be approximately 15% of the maximum air flow of the compressor) is discharged to the atmosphere with minimum resistance via discharge valve 102 along path IP2. The open position 104c of the governor valve will also be referred to as an EOD input venting position or configuration as it is the position the valve 104 is in when it actuates the discharge valve 102 to vent the EOD input to atmosphere.

[0056] The compressor idler 11 keeps the compressor 10 in this idle (energy saving) mode as long as pressure is applied. For normal operation, the compressor idler 11 must be connected to the atmosphere and this is done through governor valve 104 when in closed position 104a.

[0057] FIG. 5 shows an overpressure protection mode.

[0058] If the pressure in the EOD inlet rises to a level above a permitted operating pressure, discharge valve 102 is opened via path OP1 so that the connection of the EOD inlet and compressor 10 to the atmosphere is opened (indicated by path OP2). This function is a safety function when the electronic control fails, or a blockage occurs which would also result in an incorrect pressure detection at pressure sensors 32,42. In a non-limiting example, the discharge valve 102 may be arranged to connect the EOD inlet to atmosphere when the pressure in the EOD inlet rises to around 19 bar (1900 kPa).

[0059] FIG. 6 shows a non-loading, regeneration mode.

[0060] The granules in the cartridge of dryer unit 101 can be regenerated by passing a purgative air flow through the cartridge in the reverse direction. Regeneration through the cartridge of dryer unit 101 may be achieved by using air from consumer reservoirs 31, 41 or any other reservoir connectable in a similar manner. For example, the EOD 100 may be provided with its own regeneration reservoir. Governor valve 104 is opened to position 104c first so that the compressor 10 is brought into the idle mode (as explained above for the idle mode) and air flows along path I Pl. In addition, regeneration valve 103 is moved from its closed position 103a (biased by spring 103b) to the open position 103c by energizing solenoid 103d so that air from the consumer branch 20 (or other source of air used for regeneration) can by-pass the check valve 105 and enter the cartridge of dryer unit 101 along path RP1 to pass through the dryer unit in the opposite direction to the first direction. As discharge valve 102 is already opened to position 102c via path I Pl, DPI and port 102d, the air regenerating the dryer unit cartridge 101 and any air coming from the compressor 10 in the idle mode is discharged to the atmosphere.

[0061] In the know pneumatic air supply system 9 described above, the compressor is permanently coupled to an internal combustion engine so that the compressor is always being driven so long as the engine is running and the idle mode of the compressor is triggered pneumatically when the EOD governor valve 104 is opened. This also actuates the discharge valve 102 to connect the inlet of the EOD to atmosphere. The idle mode of the compressor 10 is stopped when the governor valve 104 is closed, which also closes the discharge valve. Accordingly, as the system starts to change from a non-loading mode, i.e, a holding mode or a regeneration mode, to the loading mode, the compressor has to work against the full load of the consumers.

[0062] This disclosure relates to control of a pneumatic air supply system having a switchable drive compressor in which drive to the compressor is switched off when the compressor is in an idle mode and is switched on when the compressor is in an actuated mode. If transitioning between the compressor idle mode and actuated mode were to be carried out simultaneously with closing of the discharge valve as in the prior arrangement described above,this would place very high loads on the switchable compressor drive when drive to the compressor is switched on.

[0063] This disclosure provides a pneumatic system, an example 209 of which is shown in FIG. 7.

[0064] The pneumatic system 209 comprises a switchable drive compressor 10 and an electrically operated air dryer (EOD) 200 having an input 201 fluidly connected to the compressor and an output configured to be fluidly connected to one or more consumers.

[0065] The EOD 200 comprises a dryer unit 202 and a regeneration system which as in the prior art can be operated in a loading mode in which the compressor is in an actuated mode and compressed air is driven through the dryer to the one or more consumers and at least one non-loading mode in which the input 201 to the EOD, and hence the compressor output, is fluidly connected to the atmosphere and the compressor is in an idle mode, in which drive to the compressor is switched off.

[0066] The output 208 of the EOD forms part of a consumer branch 207 which is fluidly connected to a set of consumers. In the example shown, the consumers comprise a first set 230 of primary consumers each having an associated reservoir 232, and a secondary consumer 234.

[0067] The output 208 of the EOD 200 connects to the consumers through a multicircuit protection valve system 21. The multi-circuit protection valve system can take various forms as are known in the art and may be operative to balance the pressure required to be supplied to the primary set of consumers 230 and the secondary consumers 234 and / or to cut the supply to any consumer should a consumer branch develop a leak. In this way, the integrity of the supply to the remaining consumers is maintained. Furthermore, the multi-circuit protection valve system 21 may be configured to ensure that the supply to the primary consumers is prioritized over the supply to secondary consumers, such as a tire pressure control system, TPCS, 61. Examples of multi-circuit protection valve systems are disclosed in GB1387892 to Robert Bosch GmbH and GB1563144A to WABCO Westinghouse GmbH.

[0068] In one example, the EOD has a structure and operation similar to that explained above with reference to FIGs. 2 to 6. FIG. 7 shows the use of an air dryer with the configuration shown in FIGs. 2 to 6.

[0069] Thus, the EOD 200 has a dryer unit 202 comprising a cartridge filled with drying granules, a discharge valve 203, a regeneration valve 204, a governor valve 205 and an output valve (check valve) 206. The discharge valve 203 is for selectively fluidly coupling an input 201 to the dryer unit to the atmosphere and is thus between an input side of the dyer unit 202 and a vent to the atmosphere.

[0070] The one-way output check valve 206 is located between an output to the dryer unit and a consumer branch 207 leading to an output 208 of the EOD which is fluidly connected to the one or more consumers 230, 234. The check valve allows air flow from the dryer unit 202 to the consumers in a first direction only when the EOD is operated in a loading mode. In addition, the output side of the dryer unit 202 is fluidly connected to the consumer branch 207 and EOD output 208 through the regeneration valve 204 in parallel to the check valve 206 to allow a flow through the dryer unit in a reverse direction for regeneration when the regeneration valve 204 is open. The governor valve 205 has an input port fluidly connected to the consumer branch 207 and the EOD output 208 and an output port 205a fluidly connected to a pilot control port 203a of the discharge valve 203, as indicated by the dashed line DP.

[0071] The electric connections of valves 203, 204 and 205 to the control unit 70 are indicated by dashed lines and may be wired or wireless.

[0072] The discharge valve 203, regeneration valve 204, governor valve 205, and oneway output check valve 206 correspond to and perform similar functions to the discharge valve 102, regeneration valve 103, governor valve 104, and output check valve 105 in the EOD system described above in relation to FIGs. 2 to 6.

[0073] The switchable drive compressor 10 has an energy saving idle mode used when the system pressures are such that operation of the compressor is not needed. In the idle mode, the compressor 10 is not driven, that is to say, drive to the compressor is switched off. Two embodiments of a switchable drive compressor are illustrated in FIG. 7.

[0074] In the main circuit of FIG. 7, a clutch 250 is located in the drive line between the compressor 10 and a power source 252. Drive to the compressor from the power source 252 can be selectively switched on and off by engaging and disengaging the clutch 250. Operation of the clutch is electronically controlled by the controller 70. The clutch may have an electricalactuator or it may have a pneumatic or hydraulic actuator. The compressor 10 can be placed in an idle mode by disengaging the clutch. The power source 252 can be any suitable drive source and could be an internal combustion engine, an electric motor supplied by a battery or a fuel cell, or a hybrid drive train having a combination of an internal combustion engine and an electric motor for propulsive drive of the vehicle.

[0075] FIG. 7 also shows an alternative arrangement in which the compressor 10 is driven by a motor 260. Operation of the motor 260 is controlled by electronically by the controller 70. The motor 260 may be an electric motor and the controller may have a motor controller which is able to regulate operation of the electric motor, say by varying the current and / or voltage of an electrically supply to the motor windings. When the compressor 10 is in the idle mode, the electric motor 260 may be switched off.

[0076] The motor 260 may alternatively be a hydraulic motor and the controller 70 may have a hydraulic motor control module. This may be arranged to regulate the hydraulic fluid supply to the hydraulic motor as that hydraulic motor can be switched on and off.

[0077] In all these arrangements, the drive to the compressor may be switched off, e.g., by disengaging the clutch 250 or stopping the motor 260, and switched on, e.g., by engaging the clutch or starting the motor 260. A clutch 250 is typically used for a power source 252 which continues to run when the compressor is in an idle mode as would be the case when the power source provides the motive force for the vehicle or is also used to drive other ancillary systems such as a hydraulic pump.

[0078] In the conventional control approach of FIG. 2, when the compressor 10 is in the idle state and it is necessary to supply air to the consumers, the governor valve 104 is moved to its closed position 104a. This takes the compressor 10 out of its idle state and closes the discharge valve 103 at the same time, so that the compressor starts supplying against the remaining pressure in the consumer side, including the reservoirs. This produces high loads for the compressor as it gets up to speed.

[0079] For a switchable drive compressor 10, it is desirable to switch the drive to the compressor on only against atmospheric pressure. With an EOD 200 used in combination with an electronically controlled compressor clutch 250 or with an electronically controlledcompressor motor 260, improved control of the transition between idle mode and actuated mode is enabled to address these issues.

[0080] Reducing load on the switchable drive compressor 10 during start up when transitioning from non-loading state to a loading state can be achieved by maintaining the governor valve 205 in the open position ( the EOD input venting configuration), so that the input 201 to the EOD is connected to atmosphere through the discharge valve 203 whilst drive to the compressorlO is switched on and keeping the governor valve 205 open until the compressor motor 260 reaches a suitable operating speed, or the clutch 250 is fully engaged in the case of a clutch drive compressor. The governor valve 205 can then be closed to deliver compressed air to the consumers through the EOD 200. Usually, the discharge valve 203 is already open when the EOD 200 is operating in a non-loading mode. However, if for any reason it is not when there is a need to switch drive to the compressor on, the discharge valve can be opened before drive to the compressor is switched on.

[0081] The additional time period during which the input 210 to the EOD remains connected to the atmosphere (and hence the compressor remains connected to the atmosphere) while the compressor is transitioning to the fully actuated state, is for example, of the order of magnitude of a second, for example less than 2 seconds, or less than 1 second. There is thus a delayed coupling of the output of the compressor to the consumer load, compared to the known approach, according to which the discharge valve is closed by the same pressure signal (and at the same time) that controls the compressor to transition from idle to actuated. This delay protects the compressor and its drive when drive to the compressor is switched on.

[0082] The compressor 10 is thus driven against a low pressure (atmospheric pressure) during startup. Where the compressor is driven by an electric motor 260, the motor 260 is only subject to relatively low loads during startup requiring lower starting currents so that cable cross sections can be smaller, and a maximum current tolerance can be reduced, etc. For a hydraulic motor, the power consumed during start-up will be lower, placing less strain on the hydraulic supply. For a compressor driven through a clutch 250, the clutch 250 is only subject torelatively low loads during engagement and hence it can be smaller and generate less heat than would be the case if it was engaged after the discharge valve 203 is closed.

[0083] A second control option is to provide a delay between opening the governor valve 205 and the discharged valve 203 and switching off drive to the compressor 10 when the system pressure is reached and the EOD is being placed in a non-loading mode. In this way, the input 201 to the EOD 200 is fluidly connected to the atmosphere (hence the compressor output is fluidly connected to the atmosphere) for an initial period before switching off the drive to the compressor 10. For this purpose, the governor valve 205 may again be controlled so that the compressor 10 delivers its output pressure to the ambient surroundings via discharge valve 203 just before the drive to the compressor is switched off and it is placed in an idle mode.

[0084] The time period (during which the compressor output is vented to the atmosphere before idling the compressor) is again for example of the order of magnitude of a second or seconds.

[0085] This has several advantages. With the compressor 10 connected to the ambient surroundings, humidity in the line between the compressor 10 and the EOD 200 can be blown out. Pressure in the line could also be released, prior to a new startup of the compressor.

[0086] With the compressor connected to the ambient surroundings, cooling of the circuit is also enabled. The line between compressor 10 and EOD 200 is normally provided with a certain length or with a cooling spiral to cool the air prior to reaching the dryer (because the compressor heats up the air). The delay may improve the cooling performance.

[0087] After the delay period, the drive to the compressor 10 is switched off, e.g., the clutch 150 is disengaged, or the motor 260 is stopped.

[0088] Electronically controlling the drive to the compressor 10 enables switching of the compressor to an idle mode to be separated from the pneumatic control of the discharge valve 203 allowing for alternative control strategies to be adopted which improve system operation and allow for a broader range of components to be used by reducing the loading on the compressor 10 and its drive 250, 260 as the compressor is brought out of its idle mode.

[0089] FIG. 8 shows a method of controlling a pneumatic system comprising a compressor and a regenerative electrically operated air dryer.

[0090] The method comprises operating the pneumatic system in a non-loading mode in step 300, in which the input 201 to the EOD is fluidly connected to the atmosphere, and hence the compressor output is fluidly connected to the atmosphere. The compressor is in an idle mode in this non-loading mode, that is to say drive to the compressor is switched off. For a compressor driven by an electric or hydraulic motor 260 the motor is off. For a compressor driven from a power source 252 through a clutch 250, the clutch is disengaged. At step 302, a pressure drop is sensed indicating that the pneumatic system needs to operate in the loading mode. However, before switching the pneumatic system from the non-loading mode to the loading mode, the coupling of the input to the EOD to the atmosphere, and hence the coupling of the compressor output to the atmosphere, is maintained in step 302. Usually, the discharge valve 203 is open when the EOD 200 is operating in a non-loading mode. However, if for any reason it is not when there is a need to switch drive to the compressor on, the discharge valve can be opened before drive to the compressor is switched on. This venting is maintained until the compressor 10 completes a transition from idle mode to actuated mode and either the clutch 250 is fully engaged or the motor 260 has been brought up to a suitable operating speed. The venting is then ended (by closing the governor and discharges valves), and the pneumatic system is then in the loading mode in step 304. The additional time during which the compressor output is vented is sufficient for the compressor to complete its transition from idle mode to actuated mode, for example a time period in the range 0.5 second to 2 seconds.

[0091] The method may further comprise coupling the input 201 to the EOD 200 to the atmosphere (through the discharge valve), and hence coupling the compressor output to the atmosphere, in step 306 for an initial period before starting a transition of the compressor from actuated mode to idle mode when the EOD is changing from a loading mode to a non-loading mode. After the transition, with the compressor output remaining vented, the pneumatic system is then in the non-loading mode in step 308. This initial period for example also lasts for a time period in the range 0.5 seconds to 2 seconds, although a longer time period may be used.

[0092] FIG. 9 illustrates a further example of a pneumatic system 209' according to the present disclosure. The pneumatic system 209' is substantially identical to the system 209 ofthe example shown in FIG. 7 and as described above, except for the arrangement for generating an idle control signal for the compressor, which will now be described. FIG. 9 shows a modification to the control of the compressor clutch 250 which is pneumatically actuated. In the example, the pressure at the governor valve output 205a is routed to the clutch actuator through an electrically controlled valve 280 (referred to herein as an idle mode actuation valve) and pressure control line 282. The idle mode actuation valve either delivers the output pressure from the governor valve to the clutch actuator 250 for disengaging the clutch or blocks the governor valve output (in the closed position of the valve 280 shown in FIG. 9) so that the clutch is engaged. Operation of the clutch 250 and hence operation of the compressor is thus regulated by idle mode actuation valve 280. The idle mode actuation valve 280 is controlled electrically by the control unit 70 which is electrically connected to a solenoid 280a of the valve. This enables disengagement of the clutch 250 to be delayed after the governor valve 205 is moved to the EOD inlet venting configuration by maintaining the idle mode actuation valve 280 in the closed position for the required delay period and then actuating the idle mode actuation valve 280 to the open position to disengage the clutch 250. The idle mode actuation valve 280 can also be used to engage the clutch 250 before and the governor valve 205 is moved to the closed position by moving the valve to closed position for the required delay before the governor valve 205 is closed. Accordingly, the idle mode actuation valve 280 is actuated to connect the pressure at the governor valve output 205a to the clutch 250 according the method described herein in FIG. 8. This approach combines electrical control to route a control pressure to a compressor which has a pneumatically actuated idle mode.

[0093] In the example of FIG. 10, the pneumatic system 209" is substantially identical to the system 209' of the example shown in FIG. 9 and as described above, except for the arrangement for controlling the compressor idle mode, which will now be described. FIG. 10 shows a modification to the control of the compressor idle mode in which a pressure at the output side of the EOD 200 (i.e., at the consumer side) is used to control the idle mode of the compressor. The consumer pressure is provided to an electrically actuated idle mode actuation valve 290 for selectively routing the consumer pressure to an pneumatic actuator the clutch 250 through a pressure control line 292. The idle mode actuation valve 290 either delivers theconsumer pressure to the clutch 250 for disengagement or blocks the consumer pressure (in the position of the valve 290 shown in FIG. 10) for engaging the clutch. The idle mode control of the compressor is thus controlled by switching idle mode actuation valve 290 using electrical control. The idle mode actuation valve 290 is controlled electrically by the control unit 70 which is electrically connected to a solenoid 290a of the valve. The idle mode actuation valve 290 is actuated to connect the consumer pressure to clutch 250 according to the method described above with reference to FIG. 8. This approach again combines electrical control to route a control pressure to a compressor which has a pneumatically actuated idle mode. This embodiment has the advantage that by connecting the pneumatic actuator of clutch 250 with the consumer side, a high mass flow of air can be used to actuate the clutch and switch the compressor. On the other hand, this example is less failure safe: If the idle mode actuation valve 290 should get stuck when pressurizing the clutch 250, this condition is kept permanently. Whereas, in the embodiment of FIG. 9, if the idle mode actuation valve 280 gets stuck in a the open position pressurizing the clutch 250, this condition would not be kept permanently as the connection to output port 205a of governor valve 205 would result in that the idle mode is aborted if EOD 200 is switch to a loading mode when the outlet port 205a of the governor valve is connected to ambient so that pneumatic clutch actuator is connected to ambient.

[0094] The air dryer may be of the type described above. However, it may comprise any suitable regenerative air dryer, having a dryer unit and a regeneration system.

[0095] As explained above, this disclosure may be applied to any vehicle having a pneumatic system for supplying consumers (i.e., on-board or external equipment) with pneumatic power. The vehicle may be an agricultural vehicle, such as a tractor, or other type of commercial vehicle.

[0096] By way of example, the consumers may comprise one or more selected from the following list: rear service brake; front service brake; park brake; trailer brake; tire pressure control system; cab air supply; dust discharge system.

[0097] The multi-circuit protection valve system 21 for example comprises multiple circuits, e.g. four circuits. Different circuits may operate at different pressures and may be associated with their own reservoirs. For example, the rear service brake, front service brake,pa rk / trai ler brake may each be supplied by a separate circuit. The fourth circuit may then supply the secondary consumers.

[0098] Within the scope of this application it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.

[0099] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the subject matter of this disclosure, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0100] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0101] Any reference signs in the claims should not be construed as limiting the scope.

[0102] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

Claims

CLAIMS1. A pneumatic system, comprising: a compressor (10) having an idle mode in which the compressor is not driven and an actuated mode in which the compressor is driven; an electrically operated air dryer, EOD, (200) having an input (201) fluidly connectable to the compressor (10), a dryer unit (202), an output (208) configured to be fluidly connected to at least one consumer (230, 234), a discharge valve (203) selectively operable to fluidly connect the EOD input (201) to atmosphere; and a controller (70), wherein the controller (70) is configured to switch the pneumatic system between (i) a loading mode in which the compressor is in actuated mode, the input to the EOD is not fluidly connected to atmosphere through the discharge valve, and compressed air from the compressor (10) is driven through the EOD in a first direction to the at least one consumer and (ii) at least one non-loading mode in which the input to the EOD is fluidly connected to atmosphere by the discharge valve (203) and the compressor is in idle mode, wherein the controller (70) is configured to maintain the fluid connection of the input of the EOD to the atmosphere when transitioning from the at least one non-loading mode to the loading mode until the compressor completes a transition from idle mode to actuated mode.

2. The pneumatic system of claim 2, wherein the controller (70) is configured to fluidly connect the input to the EOD to the atmosphere for an initial period before starting a transition of the compressor from actuated mode to idle mode when transitioning from the loading mode to the at least one non-loading mode.

3. The pneumatic system of claim 1 or claim 2, wherein the EOD comprises:a one-way output valve (206) between an output of the dryer unit (202) and the output (208) of the EOD, the one-way output valve configured to allow air to pass only in the first direction from the dryer unit to the EOD output (208); a regeneration valve (204) connected in parallel to the one-way output valve between the dryer unit output and the EOD output and selectively operable for bypassing the one-way output valve (206) to allow air to flow in a second direction opposite to the first direction from the EOD output through the dryer unit; and a governor valve (205) having an output port (205a) fluidly connected to a control pilot port (203a) of the discharge valve (203), the governor valve being selectively operable in a first configuration to fluidly connect the output port (205a) to the EOD output (208) so as to actuate the discharge valve (203) to connect the input to the EOD (201) to atmosphere.

4. The pneumatic system of any one of claims 1 to 3, wherein the compressor is driven by an electric motor (260) and the controller (70) comprises a motor controller for electronically controlling the electric motor.

5. The pneumatic control system of any one of claims 1 to 3, wherein the compressor (10) is driven by a hydraulic drive (260) and the and the controller (70) comprises a hydraulic controller for electronically controlling the hydraulic drive.

6. The pneumatic system of any one of claims 1 to 3, wherein a clutch (250) is provided between a power source (252) and the compressor, wherein drive to the compressor is switched on by engaging the clutch and switched off by disengaging the clutch.

7. The pneumatic system of claim 6, wherein the clutch has a pneumatic actuator, the pneumatic actuator being selectively fluidly connectable to a source of pressurized fluid via an electronically controllable idle mode actuation valve (280, 290).

8. The pneumatic system of claim 7 when dependent on claim 3, wherein the idle mode actuation valve (280) is selectively operative to fluidly connect the pneumatic clutch actuator to the output port (205a) of the governor valve.

9. The pneumatic system of claim 7 when dependent on claim 3, wherein the idle mode actuation valve (290) is selectively operative to fluidly connect the pneumatic clutch actuator to the output of the EOD (200).

10. The pneumatic control system of claim 6, wherein the power source (252) is selected from the group comprising: a) an internal combustion engine; b) an electric motor; c) a hydraulic motor; and d) a hybrid drive train.

11. A vehicle comprising: the pneumatic system of any one of claims 1 to 7; and the at least one consumer supplied by the pneumatic system.

12. The vehicle of claim 11, wherein the at least one consumer comprises at least one selected from the following list: rear service brake; front service brake; park brake; trailer brake. tire pressure control system; cab air supply; dust discharge system.

13. The vehicle of claim 11 or 12, comprising a vehicle, or a combination of a vehicle and an associated implement.

14. A method of controlling a pneumatic system comprising a compressor (10) having an idle mode in which compressor is not driven and an actuated mode in which the compressor is driven and a regenerative electrically operated air dryer, EOD, wherein the method comprises: switching the pneumatic system between:(i) a loading mode in which the compressor is in the actuated mode and compressed air from the compressor (10) is driven through the EOD in a first direction to the at least one consumer; and(ii) at least one non-loading mode in which an input (201) to the EOD is fluidly connected to atmosphere by a discharge valve (203) and the compressor is in the idle mode, wherein the method comprises: maintaining a fluid connection of the input to the EOD to atmosphere when transitioning from the at least one non-loading mode to the loading mode until the compressor completes a transition from idle mode to actuated mode.

15. The method of claim 14, further comprising fluidly connecting the input to the EOD to atmosphere for an initial period before starting a transition of the compressor from actuated mode to idle mode when transitioning from the loading mode to the at least one nonloading mode.

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