Compressed-air supply installation, pneumatic system, and method for controlling a compressed-air supply installation

A compressed air supply installation for operation of an air spring installation of a vehicle includes an air feed with an air compressor configured to supply a compressed air feed with compressed air, a pneumatic main line with an air dryer and a compressed air connection for supplying the pneumatic installation with compressed air, a purge line branching from the pneumatic main line to the compressed air feed and comprising a purge valve connected in the purge line and a purge connection for releasing air to the environment, wherein the purge valve is part of a controllable valve assembly. The controllable valve assembly with the purge valve can be pneumatically loaded with a control pressure derived from the air compressor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/001212 filed on Jun. 16, 2015, and claims benefit to German Patent Application No. DE 10 2014 009 419.7 filed on Jun. 25, 2014. The International Application was published in German on Dec. 30, 2015 as WO 2015/197169 A1 under PCT Article 21(2).

FIELD

The invention is directed to a compressed air supply installation, a pneumatic system, and methods for controlling and operating a compressed air supply installation.

BACKGROUND

Compressed air supply installations are used in vehicles of all types, in particular to supply an air spring system of a vehicle with compressed air. Air spring systems may also include ride height adjustment devices with which the distance between the vehicle axle and the vehicle chassis can be adjusted. An air spring installation of a pneumatic system cited initially comprises a number of air bellows pneumatically connected to a common line (gallery) which are able to raise the vehicle chassis when increasingly inflated, and lower it again when the fill level decreases. As the distance between the vehicle axle and vehicle chassis (or the ground clearance) increases, the spring travels become longer and even greater bumps in the ground can be overcome without contact with the vehicle chassis. Such systems are used in off-road vehicles and Sport Utility Vehicles (SUV). In particular in SUVs with very powerful engines, it is desirable to provide the vehicle firstly with comparatively low ground clearance for high speeds on the road, and secondly comparatively large ground clearance for off-road use. It is furthermore desirable to be able to implement a change in ground clearance as quickly as possible, which increases the requirements with regard to speed, flexibility and reliability of a compressed air supply installation.

A compressed air supply installation for use in a pneumatic system with a pneumatic installation, for example an air spring installation described above, is operated with compressed air from a compressed air feed, for example in a pressure level range from 5 to 20 bar. The compressed air is made available to the compressed air feed using an air compressor. The compressed air feed is pneumatically connected to a compressed air connection for supplying the pneumatic installation, and secondly pneumatically connected to a purge connection. The compressed air supply installation may be purged to the purge connection by the release of air via a purge valve assembly.

To ensure long-term operation of the compressed air supply installation, this comprises an air dryer with which the compressed air is dried. This avoids the accumulation of moisture in the pneumatic system, which at comparatively low temperatures can lead to crystallization damaging the valve, and can also lead to undesirable defects in the compressed air supply installation and in the pneumatic installation. An air dryer comprises a drying agent, normally granulate through which the compressed air can flow, so that at comparatively high pressure, the granulate can absorb the moisture contained in the compressed air by adsorption. An air dryer may also be configured as a regenerative air dryer. This may be achieved in that on each purge cycle—at comparatively low pressure—the dried compressed air from the air spring system flows through the granulate in counterflow or in co-flow relative to the filling direction. For this, the purge valve arrangement can be opened. For such a use—also called a pressure-change adsorption—it has proved desirable to configure a compressed air supply installation flexibly and at the same time reliably, in particular to allow a comparatively rapid purge with a pressure change which is nonetheless adequate for regeneration of the air dryer.

DE 35 429 74 A1 by the applicant describes a compressed air supply installation cited initially for a ride height control device for vehicles with air springs, with which, depending on the vehicle load, a predefined distance of the vehicle passenger cell from the vehicle axle can be maintained by filling and evacuating the air springs. The device contains a normally closed magnetic purge valve and a safety valve which can be controlled using the pressure in the air springs. Such a compressed air supply installation can still be improved.

A compressed air supply installation cited initially is also disclosed in EP 1 165 333 B2 in the context of a pneumatic system cited initially with an air spring installation. As well as a main purge line which can be shut off separately, this comprises a high-pressure purge line which has an additional high-pressure purge valve, as well as the main purge valve pneumatically controlled with a control valve in the main purge line, which is connected in parallel to the main purge line. The free flow cross-section of the separate high-pressure purge valve is smaller than that of the main purge valve. Such a compressed air supply installation can still be improved. It has been found that on purging such a compressed air supply installation via the high-pressure purge line, dry air is purged which is not used for regeneration of the drying agent. This equates to an unnecessary waste of dry air, in particular for the case that a flexible, fast and yet reliable actuation of the compressed air supply installation is required which is suitable for the above applications, with correspondingly high actuation rate.

All the above-mentioned solutions with a purge valve assembly in the form of a controllable magnetic valve assembly provide that, in the non-activated state of the magnetic part, the pneumatic part of the magnetic valve assembly is closed, i.e. the solutions provide a normally closed magnetic valve assembly. In particular with regard to the solution disclosed in DE 35 42 974 A1, it has been found that a normally closed magnetic purge valve assembly may be disadvantageous since, frequently, an additional pressure-limiting or safety valve must be provided in order to guarantee a reliable function. Since, in normally closed state, a relay valve of the magnetic valve assembly is closed, in individual cases this can lead to a valve body sticking on the valve seat, and in some cases the switch function of the relay valve of the magnetic valve assembly is not reliably guaranteed.

DE 39 19 438 C2 discloses a compressed air supply installation in which the air dryer can be connected to an outlet to atmosphere via an electrically actuatable valve device. The valve device has an electric control inlet which is connected to an electronic control device via an electric line with an electric control outlet; in non-activated state, the valve device is open. To inflate an air spring, the valve device assumes a switch position in which the connection of the air dryer to the outlet to atmosphere is interrupted.

DE 197 242 747 C1 discloses a ride height control device for vehicles with air springs, wherein a pneumatically controllable directional valve is provided in the pneumatic main line for switching via a control line, with an air control pressure generated by the compressor. The control line may be connected to atmosphere via a further directional valve, so that when the compressor is not running, the directional valve in the pneumatic main line can change from the one switch state which connects the compressor to the air dryer, to the other switch state which connects the air dryer to atmosphere.

SUMMARY

In an embodiment, the present invention provides a compressed air supply installation for operation of an air spring installation of a vehicle. The compressed air supply installation includes an air feed with an air compressor configured to supply a compressed air feed with compressed air, a pneumatic main line with an air dryer and a compressed air connection for supplying the pneumatic installation with compressed air, a purge line branching from the pneumatic main line to the compressed air feed and comprising a purge valve connected in the purge line and a purge connection for releasing air to the environment, wherein the purge valve is part of a controllable valve assembly. The controllable valve assembly with the purge valve can be pneumatically loaded with a control pressure derived from the air compressor.

DETAILED DESCRIPTION

A device and a method which are improved relative to the prior art are described herein. In particular, an alternative solution to the prior art is given which fundamentally avoids the disadvantages associated with a purge valve which is closed in the non-activated state. In particular, a purge and/or drying performance of the compressed air supply installation is improved, wherein the compressed air supply installation nonetheless can be constructed comparatively simply and compactly. In particular, fundamental technical unpredictabilities concerning a magnetic valve assembly are eliminated. In particular, a pneumatic part of a purge valve can function comparatively reliably but nonetheless be activated easily.

A compressed air supply installation for operation of a pneumatic installation is described herein, in particular an air spring installation of a vehicle, comprising: an air feed with an air compressor for supplying a compressed air feed with compressed air, a pneumatic main line with an air dryer and a compressed air connection for supplying the pneumatic installation with compressed air, a purge line, in particular a purge line branching from the pneumatic main line to the compressed air feed and comprising a purge valve connected in the purge line and a purge connection for releasing air to the environment, wherein the purge valve is part of a controllable valve assembly. According to the invention, it is provided that the purge valve can be pneumatically loaded, in particular directly, with a control pressure derived from the air compressor. In particular, it is preferred that the valve assembly with at least the purge valve can be pneumatically loaded, in particular directly, with a control pressure derived from the air compressor.

A pneumatically controllable valve assembly is described herein which can eliminate certain fundamental weaknesses of a magnetic valve assembly. With pneumatically controllable valve assemblies, fundamental susceptibilities to electrical interference or cable break, contact problems or similar can be avoided; in particular, a valve assembly which can be pneumatically controlled consumes no current. In particular, a valve assembly which can be pneumatically controlled and which comprises a purge valve is described herein. In addition, a control pressure for pneumatically controlled loading of the valve assembly can be derived comparatively easily as a control pressure from an air compressor. Particularly preferably, the control pressure can be derived from an air compressor.

With the pneumatic control concept, not only are electrical control lines omitted but, because the control pressure is derived directly from the air compressor, pneumatic control lines for loading the valve assembly are kept relatively simple. The concept of the invention can be implemented with a comparatively simple construction and directly connected to the air compressor. As a whole, a reduced component complexity and cost are achieved in comparison with previously known solutions, and there is also a reduced risk of failure; also, there is an improved use of installation space for the compressed air supply installation. Because of the comparatively simple design, the compressed air supply installation and control method have an efficient and energy-saving concept which can be implemented with increased functional reliability.

A compressed air supply installation results with a dryer circuit which allows a self-sealing air dryer outlet, wherein a purge magnet can be omitted. The functionality of the valve assembly self-sealing the air dryer outlet results from operation of the air compressor. According to the invention, the following are provided: opening of the purge valve in non-activated state of the valve assembly; closure of the purge valve by pneumatic loading of the valve assembly with a control pressure derived, in particular directly, from the air compressor. Expressed more concisely, a compressor-controlled purge functionality is implemented.

A method is described herein in which, to open the purge valve, a check valve, in particular a check valve arranged in the control line and/or an outlet valve of the compressor, is formed statically open such that when the compressor is not in operation, a control line is purged in the blocking direction of the check valve.

As described herein, additionally or alternatively, to close the purge valve, a check valve and/or outlet valve, in particular a check valve arranged in the control line and/or an outlet valve of the compressor, is dynamically closed such that when the compressor is in operation, a control pressure is maintained, in particular a control pressure must be maintained.

In an embodiment, in the non-activated state of the valve assembly i.e. without loading with control pressure, the purge valve is opened. In the context of a further preferred refinement, in non-activated state of the valve assembly, i.e. without loading with control pressure, the purge valve is closed. Permanently closed valves may be problematical if e.g. a valve piston has a tendency to seize or freezes onto the valve seat, but in principle these are also possible. Such susceptibilities are however in principle avoided with a purge valve which is open when the valve assembly is in the control state without control loading; the particularly preferred refinement cited above is however to be preferred in this respect.

In an embodiment, the purge valve is closed when the air compressor is in operation, and the purge valve is opened when the air compressor is not in operation. In other words, on operation of the air compressor, the air dryer outlet—because of the control pressure directly derived in operation—is closed automatically by closure of the purge valve. Conversely, when the compressor is not in operation and hence the valve assembly is in non-activated state, the purge valve is opened, e.g. under spring pressure of a valve spring, and the air dryer of the pneumatic main line and any pneumatic installation connected to the compressed air supply installation can be purged completely.

Preferably, the purge valve can be activated pneumatically with a control pressure derived directly from the air compressor, and in non-activated state of the purge valve, the purge valve is open. The refinement advantageously provides that the control pressure provided to load the valve assembly is used as a control pressure to activate the purge valve. Preferably, the control pressure is present at a control pressure connection of the purge valve.

In particular, it is proved advantageous that a pneumatic part of the purge valve is formed as a 2/2-way directional valve. In the context of a particularly preferred concrete refinement of the concept, a pneumatically activatable 2/2-way directional valve is provided as a purge valve which is open when not loaded with control pressure. Thus a gallery pressure can pass on purging. On start-up of a compressor of the air compressor, the purge valve (preferably in the form of a 2/2-way directional valve) is closed. In principle, any other purge valve suitable for direct switching of a compressed air volume may be provided insofar as this can be activated pneumatically as part of the valve assembly with a control pressure derived directly from the air compressor.

The purge valve is configured in particular for direct switching of a compressed air volume; preferably, according to a particularly preferred refinement, in a purge line it has a pressure-side valve connection and a purge-side valve connection, and a pressure control connection directly connected to a control line.

To obtain the control pressure directly derived from the air compressor, it has proved advantageous for a control line to be connected directly to a compressor chamber of the air compressor, in particular a compressor itself. The air compressor preferably comprises a compressor, for example a single-stage or two-stage compressor which comprises a compressor chamber.

In the context of a particularly preferred refinement, a control line is routed from a compressor chamber of an air compressor to a pressure control connection of a purge valve in the form of a 2/2-way directional valve, wherein when the pressure control connection is in the state not loaded with control pressure, the purge valve is open.

The valve assembly is furthermore preferably configured to allow automatic closure of the air dryer outlet on a filling function, and automatic opening of the air dryer outlet for purging of the air dryer, and preferably purging of the control line.

In the context of a particularly preferred refinement, the valve assembly comprises, in addition to the purge valve, a counter-valve with a check valve function and/or a choke. Preferably, the purge valve is connected in the purge line. The counter-valve with check function is preferably connected in a parallel line to a bypass line. The bypass line preferably comprises the choke.

In the context of a particularly preferred first variant of a refinement, the counter-valve with check function is formed as a check valve. The check valve has an opening direction for automatic pressure-loaded opening, and a blocking direction. Preferably, the check valve is formed as a shutter check valve.

In the context of a first derivative, a check valve of the valve assembly may be arranged in the control line. In particular, an arrangement of the check valve between a compressor chamber of the air compressor and a pressure control connection of the purge valve has proved advantageous. This structure is comparatively reliable and allows a defined functionality of the check valve in addition to an outlet valve of an air compressor. Advantageously, the pressure control connection of the purge valve can be loaded with control pressure in the automatic opening direction of the check valve. On pressurization of a control line via the air compressor, preferably first a check valve opens automatically in the opening direction to the pressure control connection of the purge valve.

In the context of a second variant, a compressor chamber of a compressor of the air compressor may have an outlet valve (preferably in a pneumatic feed line to the compressed air feed), in some cases, additionally or alternatively, also a connection valve (preferably in a pneumatic control line to the control connection of the purge valve) which performs the function of a counter-valve with check function of the compressor assembly, in particular alternatively to the check valve of the compressor arrangement. This derivative has the advantage that the outlet valve and/or connection valve may be used in synergy not only as such for release of a compressed air volume for the compressed air feed, but it can also perform the function of a check valve between the compressor chamber of the air compressor and the pressure control connection of the purge valve. The purge valve is preferably configured as a purely mechanical blocking valve.

In addition or alternatively to each of the derivatives above, it has proved advantageous to arrange a further counter-valve with check function, in particular a further first check valve, in a pneumatic feed line between a compressor chamber of a compressor and the compressed air connection of the pneumatic main line. In particular, the further counter-valve with check function, in particular the further check valve and/or an outlet valve, from the air compressor opens automatically in the direction of the compressed air connection. This further derivative has proved comparatively simple in construction, in particular if the further first check valve replaces the above-mentioned first check valve of the first derivative. In the latter case in particular, it has proved advantageous if a control line has no check valve.

In the context of a further derivative, the control line may branch between a compressor chamber of a compressor and the further check valve. This advantageously allows connection of the control line to the air compressor and the pneumatic feed line to the compressed air feed. In particular, the control line may be connected directly to the compressor chamber and/or directly to the pneumatic feed line to the compressed air feed.

Preferably, according to an embodiment and in particular according to the above-mentioned refinements, when the valve assembly is in activated state, it can be achieved that the compressor is in operation in order to generate a control pressure for the pressure control connection. Preferably, the control pressure is sufficient for automatic opening of a check valve against its blocking direction. Conversely, it has proved advantageous that, when the compressor is not in operation, the control line can be purged in the blocking direction of the check valve. In particular, for this a check valve has proved suitable which—in brief—is sealed dynamically and unsealed statically. In structural terms, a check valve can preferably be implemented as a shutter check valve with defined static leakage.

In particular, in a first derivative for implementing the purge function, it has proved advantageous that a purge choke is arranged in a first bypass line bypassing the check valve, through which air can flow preferably at least in the blocking direction of the check valve, in particular bidirectionally. In principle, a first bypass line having a purge choke may also be implemented in a second derivative, for example as a parallel line to the control line or as a parallel line to an above-mentioned pneumatic feed line between the compressor and the compressed air connection. The first bypass line having the purge choke may, additionally or alternatively in a third derivative, also be formed as a parallel line to a compressor chamber of a compressor, in particular as a parallel line to an outlet valve of a compressor chamber of a compressor. The first bypass line having the purge choke may, additionally or alternatively in a fourth derivative, also be formed as a parallel line to an outlet valve of a compressor chamber of a compressor, preferably connected to a feed line at least on one side, in particular on both sides. The above-mentioned four derivatives and further derivatives, not listed here, of a first bypass line with purge choke may be implemented individually or in combination.

In addition, a preferred arrangement of a first choke in the pneumatic main line and/or a second choke in the purge line has proved advantageous for the efficient purging and for dryer regeneration. Preferably, the valve assembly furthermore provides a counter-valve with check function connected in parallel to the bypass line. Preferably, a further choke is arranged in a bypass line bypassing a counter-valve with check function, through which line air can flow in the blocking direction of the counter-valve with check function, in particular bidirectionally. In particular, a check valve and/or an outlet valve and/or a connection valve—in particular a check valve arranged in the control line and/or an outlet valve and/or a connection valve of the compressor—may be formed statically open such that when the compressor is not in operation, the control line can be purged in the blocking direction of the check valve. In particular, a dynamically closed functionality of the valve assembly comprises the first check valve and the first bypass line, in particular with a further choke, such that a control pressure is maintained when the compressor is in operation; the control pressure is sufficient, even when air flows through the purge valve in the blocking direction of the check valve, for automatic opening of the first check valve against its blocking direction.

FIG. 1Ashows a pneumatic system100with a compressed air supply installation10and a pneumatic installation90, which in the present case takes the form of an air spring system for a vehicle chassis (not shown in detail) of a vehicle1000. The pneumatic installation90in the present case is shown partially in relation to an air springing system provided for an axle of the vehicle chassis. This has two bellows91which can be filled with compressed air or from which compressed air can be released, depending on the control requirements, for the air springing or ride height control. For this, the bellows91are connected to a gallery95, namely here via bellows lines91L departing from the gallery95as branch lines. The bellows lines91L branch from the gallery95, wherein each bellows line91L has a bellows valve93in the form of a directional valve. The two bellows valves93provided for an axle in the present case are combined in a double valve block98as one component. The compressed air content of the bellows91can be modified in controlled fashion by opening or closing one of the bellows valves93. Compressed air can be supplied to or extracted from the gallery95via a pneumatic line96which is connected to a compressed air connection2of the compressed air supply installation10.

The compressed air supply installation10serves to operate the pneumatic installation90, i.e. the pneumatic installation90is supplied with compressed air by the compressed air connection2, and the pneumatic installation90can be purged by the compressed air connection2.

To generate compressed air, the compressed air supply installation10provides an air feed which has an air feed connection0and an air filter0.1. A pneumatic feed line20of the air feed may supply air, received via the air feed connection0, to an air compressor21. The air compressor21in the present case has a single-stage compressor21.2driven via a motor21.1. The compressor21.2in the present case has a single compressor stage with a compressor chamber21.3, to which firstly the pneumatic feed line20of the air feed running on to the compressed air feed1, and also a pneumatic control line120, are connected via an outlet valve22.0.

A pneumatic main line60is connected to the compressed air feed1and connects the compressor feed1to the compressed air connection2. An air dryer61and a first choke64are connected to the pneumatic main line60in said order from the compressed air feed1in the direction of the compressed air connection2, i.e. in a filling direction.

A purge line70branches from the compressed air feed1, in which line firstly a second choke74and, following this in the direction of a purge connection3, i.e. in the purge direction, a purge valve71with a normally open valve piston of a pneumatic part71P, are connected. For this, the pneumatically actuatable pneumatic part71P of the purge valve71has a pressure-side valve connection X and a purge-side valve connection Y, to which the purge line70is connected on a pressure side with the second choke74, or on a purge side with a purge filter0.3. The purge valve71also has a pressure control connection71S which can be loaded with control pressure via the above-mentioned control line120. In the state of the pressure control connection71S not loaded with control pressure, the purge valve in the first switch state shown inFIG. 1Ais open between the valve connections X, Y, i.e. the purge line70is open from the compressed air feed1to the purge connection3, so that an air dryer outlet (not shown in detail) of the air dryer61is open to the purge connection3.

In the present case, between the purge-side valve connection Y and the purge filter0.3, a purge check valve72is arranged in the purge line70which serves to protect against ingress into the purge line70and to retain the pressure or limit the retention pressure on purging. The purge check valve72is optional and may if necessary also be omitted insofar as a small pressure difference should not persist on purging. This function of a check valve72may suitably be integrated in the minimum pressure valve assembly130, with omission of the latter, e.g. instead of the minimum pressure valve132, a check valve is provided similar to the check valve72, whereby the regeneration of the air dryer61is also advantageously influenced without needing to restrict the nominal width of the first choke134.

The mechanical purge valve71presented above, on application of a control pressure to the pressure control connection71S, can switch to a second switch position in which the pressure-side valve connection X and the purge-side valve connection Y in the purge line70are pneumatically separated. The second switch position to this extent serves for operation of the compressed air supply installation10for filling the pneumatic installation90from the air compressor21, i.e. from the compressed air feed via the pneumatic main line60to the compressed air connection2. In contrast, the first switch position of the purge valve71shown inFIG. 1A, in the state not loaded with control pressure, serves for purging the compressed air supply installation10or pneumatic installation90via the air dryer61.

The extract inFIG. 1Bfrom a derived compressed air supply installation10G shows a derived embodiment with a normally closed purge valve71G in the purge line70, forming a closed valve assembly40G according to a variant; this serves to implement a self-reinforcing closing functionality. Otherwise, for the same or similar parts, or components of the same or similar function, the same reference numerals are used and reference is made to the corresponding parts of the description. In particular, the drawing shows with dotted lines—merely for the sake of clarity—an advantageous control line or branch line120,120′ and bypass line123,123′; the same applies to connected lines of similar or comparable function.

The normally closed purge valve71G always holds the normally closed valve piston of the pneumatic part71P closed with a relatively weak valve spring76. In other words,FIG. 1Bshows the normally closed purge valve71G in which the valve spring76merely overcomes friction to create a defined starting position. In operation, the pneumatic force on the back of the piston—more generally, the side of the pneumatic part71P on the side of the pressure control connection71S—is greater than on the underside of the piston (e.g. in an annular chamber) on the side of the pressure counter-control connection71A. The pressure counter-control connection71A is connected to the counter-pressure control line160which branches from the pneumatic main line60as a branch line. The purge valve71in this embodiment thus remains closed on filling. When the air compressor21stops, the air holding the piston closed under the pressure force on the pressure control connection71S escapes via the choke121until the dryer interior pressure brings the piston (more generally, the pneumatic part71P) of the purge valve71—and hence the purge valve71—into the open purge position. When the pressure has diminished, the valve spring76restores everything to the unactuated starting position as shown inFIG. 1B. The check valve122G here serves to limit pressure, a function which would otherwise have to be guaranteed by the relay piston of the pneumatic part71P.

In both the embodiment shown inFIG. 1Aand that inFIG. 1B, on start-up of the air compressor21and hence on rising pressure and control pressure in the control line120, the bypass line123,123′ acts to reinforce the seal of the valve piston. On sufficiently high pressure in the bypass line123,123′, however, a further pressure rise from opening of the check valve122in the control line120(FIG. 1A) or the check valve122G in the branch line120′ of the control line120(FIG. 1B) to the purge connection3, is prevented. Then only the dryer interior pressure rises, as symbolized this case via the dryer interior pressure line75, until the area-dependent state of equilibrium is achieved or overcome; thus a pressure limitation is active. After the compressor has stopped, the statically unsealed bypass line123,123′ reduces the pressure and the valve piston of the pneumatic part71P is raised against the weak spring force of the valve spring76by the dryer interior pressure—present in the dryer interior pressure line75—and purged in accordance withFIG. 1B. In a derived embodiment, instead of or in addition to the leakage of the bypass line123,123′, a small magnet may also be used to make the purge system statically unsealed at the purge valve71G. Thus high pressures can be handled with relatively small spring forces, and the elastomer seals are only loaded lightly in rest state.

In principle, the variant shown inFIG. 1Bof a compressed air supply installation10G may be used to implement a self-reinforcing closing functionality, i.e. with a normally closed purge valve71G in the purge line70, with the pneumatic components described, in particular the check valve122G and the purge choke121of the valve assembly40G—also in the embodiments described as variants below with reference toFIG. 2andFIG. 3AandFIG. 3B.

Further additionally, with reference toFIG. 1AandFIG. 1B, in order to implement a purely pneumatic activation of the purge valve71,71G according to a concept of a compressor-controlled purge functionality, the purge valve71,71G may be part of a valve assembly40,40G which, in addition to the purge valve71,71G, also comprises a check valve122arranged in the control line120(as shown inFIG. 1A), which is also called the first check valve122.

The check valve122, formed in the present case according toFIG. 1Afor example as a shutter check valve, is dynamically sealed and statically unsealed. To create the static leakage, a first bypass line123to the control line120is formed which bypasses the first check valve122, and in which a bidirectional purge choke121is arranged, through which air can flow in particular in the blocking direction of the first check valve122. A control pressure present at the pressure control connection71S can thus be purged in the blocking direction of the first check valve122via the purge choke121and the first bypass line123. A purge flow of the control pressure may for example escape into the compressor chamber21.3of the compressor21.2. The purge flow may be guided to the environment in the direction of the filter0.1and the air feed connection0. The purge flow of the control pressure may, additionally or alternatively, also be guided by the compressed air feed1into the purge line70to the purge connection3. This applies in particular if the pressure in the bypass line123is so low that the air dryer61is already open or opened via the spring force at the valve piston of the purge valve71. In the manner described here or in a similar manner, a residual purge of the bypass line123can take place.

Secondly, the first check valve122in the present case is dynamically closed such that, on operation of the compressor21.2—despite the purge valve121with bidirectional air flow—a control pressure is maintained at the pressure control connection71S. In other words, on operation of the compressor21.2, a sufficient control pressure is built up for automatic opening of the check valve122against its blocking direction, and applied to the pressure control connection71S; this takes place even when air flows through the purge choke121against the blocking direction of the check valve122.

Individually, the pneumatic control function of the purge valve71takes place as follows. In non-activated state of the valve assembly40, i.e. without pressure-loading of the valve assembly40, the pressure control connection71S of the purge valve71is not loaded with control pressure; the purge valve71is then in the first switch state shown inFIG. 1A, i.e. open, in which the purge line70is open between the pressure-side valve connection X and the purge-side valve connection Y through to the purge connection3. An air dryer61or gallery95or the bellows91of a pneumatic installation can be purged as soon as one of the bellows valves93opens. A purge flow can escape from the bellows91via a bellows valve93into the gallery95and the pneumatic line96and the main pneumatic line60, with regeneration of the air dryer61, into the purge line70and the purge valve71to the purge connection3, to the environment.

As soon as the bellows91of the pneumatic installation90is filled, the air compressor21begins operation; for this, the electric motor21.1drives the compressor21.2which provides compressed air at a compressed air feed1via the outlet valve22.0. A corresponding pressure is also present in the control line120and opens the first check valve122in the automatic opening direction. The first check valve122is dynamically closed on operation of the compressor21.2because of the configuration with the bypass line123and the choke121. In other words, operation of the compressor21.2is sufficient to build up a pressure in the compressor chamber21.3which is sufficient for a control pressure to be present at the control pressure connection71S. The control pressure is sufficiently high to transfer the actuatable pneumatic part71P of the purge valve71from the first switch position shown inFIG. 1Ato a second switch position, in which the pressure-side valve connection X and the purge-side valve connection Y are pneumatically separated; i.e. the purge line70is closed. In this way, the purge line70is pneumatically interrupted by the purge valve71, i.e. the dryer outlet of the air compressor61or the compressed air feed1is pneumatically separated from the purge connection3. Thus sufficient compressed air—dried in the air dryer61—can be provided via the compressed air feed1and via the first choke64at the compressed air connection to fill the pneumatic installation90.

FIG. 2shows a further embodiment of a compressed air supply installation10′ in which the first choke64is replaced or modified by a minimum pressure valve assembly130. Otherwise, for the sake of simplicity, the same reference numerals are used for the same or similar parts of the pneumatic system100′ and the compressed air supply installation10′ and the pneumatic installation90′, or for parts of identical or similar function. With regard to these features, for the description ofFIG. 2, reference is made to the corresponding parts of the description ofFIG. 1A.

With regard to the pneumatic installation90′, here—as well as four bellows91—a pressure accumulator92is provided, upstream of which an accumulator valve94in the form of a directional valve is connected in an accumulator line92L branching as a branch line from the gallery95. The bellows valves93and the accumulator valve94in the present case are combined in a quintuple valve block98′.

The minimum pressure valve assembly130provides a check valve62connected in the pneumatic main line60and also called a second check valve, which is bypassed by means of a second bypass line133, i.e. the second bypass line133connects to the pneumatic main line60on the pressure side between the air dryer61and check valve62, and on the air connection side between the check valve62and the compressed air connection2. A minimum pressure valve132and a first choke134—through which air can flow only in one direction because of the minimum pressure valve132—are arranged In the second bypass line133. The minimum pressure valve132opens in the blocking direction of the check valve62. A compressed air connection2can be loaded with compressed air from a compressed air feed1against the blocking direction of the second check valve62—i.e. automatically opening—e.g. for filling a gallery95. In other words, because of the minimum pressure valve assembly130, when the pneumatic installation90′ is filled by means of the automatically opening second check valve62, under the delivery pressure of the compressor21.2, the full line cross-section of the pneumatic main line60is opened. On purging however, after overcoming a minimum pressure (depending on the configuration of the minimum pressure valve132), the first choke134is active. To purge the pneumatic installation90′, a purge flow of compressed air can escape via the minimum pressure valve132and the first choke134. A purge flow is used to regenerate the air dryer61and is guided further into the purge line70via the second choke74and the purge valve71to the purge connection3.

In all embodiments shown here of a pneumatic system—in particular both in the embodiment shown inFIG. 2of a pneumatic system100′ with a compressed air supply installation10′ and a pneumatic installation90′, and also in an embodiment explained below of a pneumatic system100″ with a compressed air supply installation10″ and a pneumatic installation90″—an accumulator92in one or more bellows91can be refilled; however, in particular in the embodiments shown inFIG. 2andFIG. 3A, this only works advantageously if the compressor21.2has first been started and a minimum pressure built up which closes the purge, i.e. the purge line70is closed by pneumatic activation of the purge valve71via the pneumatic control line. In comparison with a “mechanical” blocking of the gallery95implemented directly in the pneumatic main line60by a blocking valve, this procedure requires slightly more energy since, instead, a “pneumatic blocking” of the gallery is simulated; the procedure however prevents an air loss and makes refilling possible.

FIG. 3AandFIG. 3Bshow further embodiments of a modified compressed air supply system10″ in detail A and detail B respectively, for a pneumatic system100″ with a pneumatic installation90″ of a vehicle1000″. In the present case, for the sake of simplicity, the same reference numerals are used for identical or similar features, or features of identical or similar function. For a description of the corresponding parts ofFIG. 3AandFIG. 3B, reference is made to the description ofFIG. 2and the description ofFIG. 1A. Detail A and detail B ofFIG. 3AandFIG. 3Bare described more extensively below.

Detail A ofFIG. 3Ashows a derived embodiment of a valve assembly40″ with correspondingly modified connection of the control line120to the compressor21.2. It is evident in detail A that the control line120connects directly to a connection valve22of the compressor chamber21.3of the compressor21.2. The connection valve22to this extent takes over the functionality of the first check valve122shown inFIG. 1AandFIG. 2. In addition, in the present case, amongst other purposes to limit residual pressure, a further first check valve23is arranged in the pneumatic feed line20between the outlet valve22.0and the compressed air feed1. This structure is shown enlarged inFIG. 3B. The result is a simplified embodiment in which the outlet valve22.0and/or connection valve22may be used in synergy so that, after automatic opening thereof to the control line120, a suitable control pressure can be built up at the pressure control connection71S of the purge valve71.

FIG. 3Ashows a first bypass line123with the purge choke121formed as a parallel line to the pneumatic feed line20of the air feed, wherein the pneumatic feed line20runs between the air feed connection0and the compressed air feed1. The derived first bypass line123branches from a connection20.1of the pneumatic feed line20, and leads to a connection120.1of the control line120, bypassing the air compressor21. In this case too, the outlet valve22.0performing the functionality of the check valve is to this extent formed as a statically open valve, i.e. a control pressure present at the pressure control connection71S can, when operation of the compressor21.2has stopped, escape via the bypass line123and the purge choke121at the connection20.1of the air feed line20, and from there to the air feed connection0, and the control line120is purged accordingly.

Similarly,FIG. 3B—as shown in detail B—provides a further derived bypass line123′ which is formed as a bypass line to the outlet valve22.0. Here the control line120can be purged of a control pressure—bypassing the outlet valve22.0—via the bypass line123′ into the air compressor21, e.g. into the compressor chamber21.3(bypass line123′ and purge choke121′ shown in dotted lines), or also into a part of the air feed line20after the air feed connection0and before the compressor chamber21.3(bypass line123and purge choke121). In a derivative of both cases, the purge choke121,121′ may in particular be formed as an integrated choke in the outlet valve22.0of the compressor21.2. A pressure limitation may be implemented via the design of the area ratios, taking into account the purge choke121,121′. The pressure limitation here extracts a pressure via the pneumatic bypass line123,123′ after the compressor21.2—in concrete terms, between the outlet of the compressor chamber21.3and the compressed air feed1—which is compensated via the choke121,121′ if a threshold pressure is exceeded. At high pressures, the defined leakage via the choke121,121′ prevents a further pressure rise in the bypass line123,123′, and the sufficiently high dryer interior pressure can lift the valve piston of the pneumatic part71P of the purge valve71. Here, in allFIGS. 1A to 3A, a dryer interior pressure is indicated symbolically via the dryer interior pressure line75, which always lies on the underside of the valve piston of the pneumatic part71P of the purge valve71in the direction of the spring pressure of the valve spring of the purge valve71.

FIG. 4shows diagrammatically, in a flow diagram E, the basic sequence of steps E1to E4for purging a pneumatic installation90,90′,90″ or an air dryer61. For this it is provided that in a first step E1, a compressor21.2of an air compressor21is stopped, i.e. is not in operation. Accordingly, in a second step E2, it is provided that a control line120via a purge choke122is statically open. If a control pressure is applied at a pressure control connection71S of a purge valve71in the control line, this can be purged in the second step E2, past said first check valve122. In a third step E3, accordingly the purge valve71is in a state not activated by control pressure and hence open between the pressure-side valve connection X and the purge-side valve connection Y. In a fourth step E4, by opening one of the bellows valves93, a bellows91—or by opening an accumulator valve94, an accumulator92—can be purged to a purge connection3, in some cases with regeneration of the dryer61.

View B ofFIG. 4shows a first flow diagram B for filling a pneumatic installation90,90′,90″. In a first step B1, this provides the starting of a compressor21.2which compresses air in a compressor chamber21.3. By opening an outlet valve22.0with the functionality of a check valve, or a connection valve22of the valve chamber21.3, or a check valve122in a control line120to the pressure control connection71S of the purge valve71, in a second step B2a control pressure can be built up to activate the purge valve71. An outlet valve22.0or connection valve22of a compressor is here preferably still closed in the direction of a compressed air feed1, i.e. a check valve122in a control line120opens before a pressure valve or outlet valve of the compressor, in order to first build up a control pressure. In a third step B3, the purge valve71closes, i.e. transfers from a non-actuated, open first switch position (as shown inFIG. 1AorFIG. 3A) into a pneumatically actuated, closed second switch position, in which the pressure-side valve connection X and the purge-side valve connection Y are pneumatically separated. In a fourth step B4, with the purge line70thus closed and the compressor still in operation, i.e. with a compressor pressure exceeding the actuation pressure (control pressure) of the purge valve71—in particular with the outlet valve or pressure valve of the compressor opening—compressed air can be made available to the compressed air feed1and applied at the compressed air connection2via the air dryer61and the first choke64or via the automatically opening second check valve122. Finally, via the compressed air connection2, a gallery95of the pneumatic installation90,90′,90″—or if the bellows valve93is open, a corresponding bellows91—can be filled with compressed air.

LIST OF REFERENCE NUMERALS

0Air feed connection

1Compressed air feed

2Compressed air connection

10,10′,10″,10G Compressed air supply installation

20Pneumatic feed line

22Connection valve, in particular with check valve function, in control line120

23Further check valve

40,40′,40″,40″A,40″B,40G Valve assembly

60Pneumatic main line

62(Second) check valve in pneumatic main line60

71P Pneumatic part

71S Pressure control connection on piston top side

71A Pressure counter-control connection on piston underside

72Optional purge check valve

75Symbolic dryer interior pressure line

76Valve spring of purge valve71,71G

91L Bellows line as branch line

92L Accumulator line as branch line

93Bellows valve as directional valve

94Accumulator valve as directional valve

100,100′,100″ Pneumatic system

102,102′ Pneumatic system

120,120′ Pneumatic control line, branch line

122,122G (First) check valve in control line120

123,123′ First and further (second) bypass line

130Minimum pressure valve assembly

132Minimum pressure valve

133Second bypass line

160Counter-pressure control line

A, B Detail

X Pressure-side valve connection

Y Purge-side valve connection