Abstract:
An air spring system is disclosed. The air spring system has a compressor, which has a suction side and a delivery side, a pressure reservoir, a first valve device and a second valve device. Each valve device is connected between the compressor and the pressure reservoir. In order to provide the air spring system, which is of simple construction and can be produced economically, the first valve device and the second valve device are each embodied as 3/2-way valves.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This U.S. patent application claims priority to German Patent Application DE 10 2010 008748.3, filed Feb. 20, 2010, which is incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The invention relates to an air spring system having a compressor, which has a suction side and a delivery side, having a pressure reservoir and having a first valve device and a second valve device, which are connected between the compressor and the pressure reservoir. The invention furthermore relates to a motor vehicle having an air spring system of this kind. 
     BACKGROUND OF THE INVENTION 
     Air spring systems operate either with a closed or an open control loop. In the case of open air spring systems, air is drawn in from the environment by a compressor and delivered to air springs of a motor vehicle in order to raise the motor vehicle. For discharge, the air is discharged to the environment, for example. It is possible here to use a pressure reservoir to enable the motor vehicle to be raised even without the compressor, if required. In closed air spring systems, air is conveyed backwards and forwards between a pressure reservoir and the air springs in order to raise or lower the motor vehicle. Owing to leaks, it may be necessary to replenish the system with air from outside, even in a closed air spring system. The additional air can be fed into the pressure reservoir or directly into the air springs. In this system, account must be taken of the fact that the air flows under pressure through an air drier as the system is filled. During discharge, the air should be discharged to the environment through the drier in order to remove the moisture that has accumulated in the drier and regenerate the drier. German Patent DE 10 2004 038 705 B3, which is incorporated by reference herein, has disclosed a compressed air system for a motor vehicle which is used to supply air-operated loads. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an air spring system which is of simple construction and can be produced economically. 
     This object is achieved in an air spring system having a compressor, which has a suction side and a delivery side, having a pressure reservoir and having a first valve device and a second valve device, which are connected between the compressor and the pressure reservoir, in that the first valve device and the second valve device are each embodied as 3/2-way valves. The use in accordance with the invention of the 3/2-way valves makes possible a simple pneumatic circuit. The arrangement in accordance with the invention of the 3/2-way valves enables the motor vehicle to be raised directly, even when the air spring system is empty. This provides the advantage that it is not necessary to fill the pressure reservoir before raising the motor vehicle, thereby considerably shortening unwanted waiting times. 
     A preferred illustrative embodiment of the air spring system is characterized in that the first valve device is connected between the suction side of the compressor and the pressure reservoir. The first valve device is preloaded, preferably by a spring, into a control position in which the pressure reservoir is connected to the suction side of the compressor. The first valve device is preferably electromagnetically actuable. 
     Another preferred illustrative embodiment of the air spring system is characterized in that the first valve device is connected to the second valve device by a first valve connecting line and a second valve connecting line. Via the two valve connecting lines and the two valve devices, the pressure reservoir can be connected to at least one air spring. 
     Another preferred illustrative embodiment of the air spring system is characterized in that the second valve device is connected between the delivery side of the compressor and at least one air spring. The second valve device is preferably assigned a plurality of air springs. The second valve device is preloaded, preferably by a spring, into a control position in which a port for the air spring is connected to the first valve connecting line. The second valve device is preferably electromagnetically actuable. 
     Another preferred illustrative embodiment of the air spring system is characterized in that an air spring valve is connected between the second valve device and the air spring. The air spring valve is preferably a 2/2-way valve with an open position and a closed position. In the closed position, the connection between the second valve device and the air spring is interrupted while, in the open position, the connection is open. 
     Another preferred illustrative embodiment of the air spring system is characterized in that the second valve connecting line is connected to an intake line via a check valve. An air filter can be arranged in the intake line. The check valve allows air to be drawn in from the environment and prevents unwanted escape of air from the air filter system into the environment. 
     Another preferred illustrative embodiment of the air spring system is characterized in that the first valve connecting line is connected to the delivery side of the compressor. Like the second connecting line, the first connecting line is connected both to the first valve device and to the second valve device. 
     Another preferred illustrative embodiment of the air spring system is characterized in that the first valve connecting line is connected to a discharge line via a discharge valve. The discharge valve is preferably embodied as a 2/2-way valve with an open position and a closed position. In the open position of the discharge valve, air can be discharged from the air spring system. The discharge valve is preferably preloaded into a closed position, in which the discharge line is closed. 
     Another preferred illustrative embodiment of the air spring system is characterized in that a one-way restrictor device and an air drier are connected in series between the first valve connecting line and the delivery side of the compressor. In the one-way restrictor device, a check valve and a restrictor are connected in parallel. The check valve prevents air from flowing back to the return side of the compressor in an unrestricted way. A check valve can be connected between the one-way restrictor device and the air drier, preventing unwanted backflow through the drier. 
     The invention furthermore relates to a motor vehicle having an air spring system as described above. The motor vehicle preferably has two, in particular four, air springs, to each of which an air spring valve is assigned. 
     Further advantages, features and details of the invention will emerge from the following description, in which various illustrative embodiments are described specifically with reference to the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawing: 
         FIGS. 1 to 9  show different illustrative embodiments and states of air spring systems according to aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIGS. 1 to 9 , different illustrative embodiments and states of an air spring system according to aspects of the invention are shown in the form of pneumatic circuit diagrams. The air spring system comprises a compressor  1  with a suction side  2  and a delivery side  3 . The suction side  2  of the compressor  1  can be connected to a pressure reservoir  8  via lines  5 ,  6 . Lines  5 ,  6  are pneumatic lines, as are further lines described below. 
     A first valve device  11  is connected between the suction side  2  of the compressor  1  and the pressure reservoir  8 . The first valve device  11  is embodied as a 3/2-way valve. Lines  5  and  6  are connected to two ports of the first valve device  11 . A first valve connecting line  21  is connected to the third port of the first valve device  11 . Via the first valve connecting line  21 , the first valve device  11  is connected to a second valve device  12 . 
     The second valve device  12  is likewise embodied as a 3/2-way valve. Connected to the second valve device  12  is a second valve connecting line  22 , which connects the two valve devices  11 ,  12  in parallel with the first valve connecting line  21 . 
     Two air springs  27 ,  28  of a motor vehicle are connected to a port of the second valve device  12  via air spring valves  25 ,  26 . The two air spring valves  25 ,  26  are each embodied as 2/2-way valves with a closed position and an open position. In the open position, the air spring  27 ,  28  assigned to the air spring valve  25 ,  26  is connected to the second valve device  12 . 
     Branching off from the second valve connecting line  22  is an intake line  34  fitted with a check valve  30  and an air filter  32 . Via the intake line  34 , it is possible for air, for example, to be drawn into the otherwise closed air spring system from the environment. The check valve  30  prevents unwanted escape of air from the closed air spring system into the environment. 
     The first valve connecting line  21  is connected to the delivery side  3  of the compressor  1  via a line  40 . Starting from the first valve connecting line  21 , a one-way restrictor device  41  and an air drier  42  are arranged in series in line  40 . 
     The one-way restrictor device  41  comprises a check valve arranged in line  40  and a restrictor arranged in parallel thereto. The check valve in the one-way restrictor device  41  prevents air from flowing into the air drier  42  in an unrestricted way. 
     A discharge line  44  with a discharge valve  45  branches off from line  40  between the delivery side  3  of the compressor  1  and the air drier  42 . The discharge valve  44  is embodied as a 2/2-way valve with a closed position and an open position. 
     The electromagnetically actuable discharge valve  45  is preloaded into its illustrated closed position, in which the discharge line  44  is closed, by a spring, for example. When the discharge valve  45  is actuated, the discharge valve  45  switches to its open position, in which the discharge line  44  is opened to the environment, for example. 
     The pressure in line  40  is detected by a pressure sensor  50  between the one-way restrictor device  41  and the first valve connecting line  21 . 
     The air spring system shown in  FIGS. 1 to 9  makes available a particularly efficient and hence economical pneumatic circuit, which makes possible the following functions inter alia: delivery of air from the at least one pressure reservoir  8  or from two pressure reservoirs to at least one of the air springs  27 ,  28  with the compressor  1 ; transfer of air from the at least one pressure reservoir  8  to at least one of the air springs  27 ,  28  through the stationary compressor  1 , using a pressure gradient; delivery of air from at least one of the air springs  27 ,  28  to the at least one pressure reservoir  8  with the compressor  1 ; transfer of air from at least one of the air springs  27 ,  28  to the at least one pressure reservoir  8  through the stationary compressor  1 , using a pressure gradient; transfer of air from the at least one pressure reservoir  8  to at least one of the air springs  27 ,  28 , bypassing the compressor  1 , using a pressure gradient; transfer of air from at least one of the air springs  27 ,  28  to the at least one pressure reservoir  8 , bypassing the compressor  1 , using a pressure gradient; delivery of air from the environment when the pressure reservoir  8  is empty to at least one of the air springs  27 ,  28 , with the induced air being dried in the air drier  42 ; discharge of air from at least one of the air springs  27 ,  28  to the environment, with regeneration of the air drier  42 ; delivery of air from the environment to the at least one pressure reservoir  8 , with the induced air being dried in the air drier  42 ; discharge of air from the at least one pressure reservoir  8  to the environment, with regeneration of the air drier  42 ; measurement of the pressure in the at least one pressure reservoir  8  with the aid of the pressure sensor  50 ; measurement of the pressure in at least one of the air springs  27 ,  28  with the aid of the pressure sensor  50 . 
     The way in which the closed air spring system is raised is shown in  FIG. 1 . In the illustrated state of the circuit, the pressure reservoir  8  is connected to the suction side  2  of the compressor  1  via the first valve device  11 . The first valve connecting line  21  is likewise connected to the suction side  2  of the compressor  1  via line  5 . This allows air transfer from the pressure reservoir  8  to the air springs  27 ,  28  through the compressor  1 . The reservoir pressure of the pressure reservoir  8  keeps the check valve  30  in the intake line  34  closed. During raising, the compressor  1  can be stationary or in operation. 
     The way in which the closed air spring system is lowered is shown in  FIG. 2 . The two air springs  27 ,  28  are connected to the suction side  2  of the compressor  1  via the second valve device  12  and the second valve connecting line  22 . The pressure reservoir  8  is connected to the delivery side  3  of the compressor  1  via the first valve device  11 , and the first valve connecting line  21  is connected to the delivery side  3  of said compressor  1  via the one-way restrictor device  41  and the air drier  42 . Transfer of air from the air springs  27 ,  28  to the pressure reservoir  8  takes place via the compressor  1 . The air spring pressure closes the check valve  30  in the intake line  34 . Lowering can be accomplished by way of the operating compressor  1 . However, lowering can also be accomplished without the compressor  1 , using a pressure gradient. 
       FIG. 3  shows how the open air spring system is raised, with the air being dried and with the pressure reservoir  8  empty. The two air springs  27 ,  28  are connected to the delivery side  3  of the compressor  1  via the second valve device  12  and line  40 . The suction side  2  of the compressor  1  is connected to the empty pressure reservoir  8  via the first valve device  11 . The vacuum caused by air induction opens the check valve  30  in the intake line  34 . The induced air flows under pressure through the air drier  42  and releases moisture. As the air springs  27 ,  28  are filled, the air spring pressure is measured with the aid of the pressure sensor  50 . 
     The way in which the open air spring system is lowered with drier regeneration is shown in  FIG. 4 . The discharge valve  45  is in its open position, allowing air to escape via the discharge line  44 . Owing to the pressure gradient relative to the air spring pressure, which is detected with the pressure sensor  50 , the check valve  30  in the one-way restrictor device  41  closes. The decompressed air can thus escape via the restrictor of the one-way restrictor device  41 , through the drier  42  and the discharge line  44 . The pressure reservoir  8  is connected to the suction side  2  of the compressor  1  via the first valve device  11 . 
       FIG. 5  shows how the pressure reservoir  8  is filled, with the air being dried and the pressure being measured. The pressure reservoir  8  is connected to the delivery side  3  of the compressor  1  via the first valve device  11 , the first valve connecting line  21  and line  40 . The two air spring valves  25 ,  26  are closed. The suction side  2  of the compressor  1  is connected to the intake line  34  via line  5  and the second valve connecting line  22 . The vacuum caused by air induction opens the check valve  30  in the intake line  34 . The induced air flows under pressure through the air drier  42  and releases moisture. As the pressure reservoir  8  is filled, the reservoir pressure is measured by means of the pressure sensor  50 . 
     The way in which the pressure reservoir  8  is emptied, with drier regeneration, is shown in  FIG. 6 . The pressure reservoir  8  is connected to line  40  via the first valve device  11  and the first valve connecting line  21 . The two air spring valves  25 ,  26  are closed. The discharge valve  45  is open. The pressure prevailing in the discharge line  45  is therefore ambient pressure. The pressure difference causes the check valve of the one-way restrictor device  41  to close. Decompressed air flows via the restrictor of the one-way restrictor device  41 , through the drier  42  and via the discharge line  45  into the environment. Owing to the backpressure ahead of the one-way restrictor device  41 , the reservoir pressure can be measured with the pressure sensor  50 . 
       FIG. 7  shows how the pressure in the pressure reservoir  8  is measured with the pressure sensor  50 . The pressure reservoir  8  is connected to the delivery side  3  of the compressor  1  via the first valve device  11 , the first valve connecting line  21  and line  40 . The connection between the first valve connecting line  21  and the air springs  27 ,  28  is interrupted by the second valve device  12 . The air spring valves  25 ,  26  are closed. 
       FIG. 8  shows how the pressure in air spring  27  is measured with the pressure sensor  50 . Air spring valve  26  is closed. Air spring valve  25  is open. Air spring  27  is connected to the delivery side  3  of the compressor  1  via the opened air spring valve  25 , the second valve device  12  and line  40 . The connection between the first valve connecting line  21  and the pressure reservoir  8  is interrupted by the first valve device  11 . 
       FIG. 9  shows how the closed air spring system can be raised or lowered through air transfer, with the compressor  1  being bypassed. Air spring valve  26  is closed. Air spring valve  25  is open. Air spring  27  is connected to the pressure reservoir  8  via the opened air spring valve  25 , the second valve device  12 , the first valve connecting line  21  and the first valve device  11 . A pressure balance can thus be brought about through air transfer from air spring  27  to the pressure reservoir  8  or, conversely, from the pressure reservoir  8  to air spring  27 . Since the compressor  1  is bypassed during air transfer, it can remain switched off.