Patent Publication Number: US-9422856-B2

Title: Valve device for controlling the air intake for a compressor of a vehicle, and compressor system and method for controlling a compressor system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/EP2011/072066, filed Dec. 7, 2011, which claims priority under 35 U.S.C. §119 from German Patent Application No. DE 10 2010 055 692.0, filed Dec. 22, 2010, the entire disclosures of which are herein expressly incorporated by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a valve device for controlling the air intake for a compressor of a vehicle. The invention also relates to a compressor system including a valve device of this type, and also to a method for controlling an air intake for a compressor of a compressor system of a vehicle. 
     In modern vehicles, in particular commercial vehicles, systems operated with compressed air are often used. Systems of this type are found, for example, in brake systems and suspension systems. To generate and prepare the compressed air, compressed air preparation systems are used, which for example generate, filter and store compressed air and forward it onto the corresponding systems. Compressed air preparation systems of this type are used, for example, in lorries, rail vehicles and tractors and include a compressor and associated components of a compressor system in order to pressurize air. In order to achieve an efficient utilization of energy from a central drive device, such as an engine, turbochargers are often used in vehicles of this type. Energy can be drawn, for example, from an exhaust gas flow via a turbocharger. It is already known to use a turbocharger to precompress air before it is fed to the compressor of the compressed air preparation device or to the compressor system in order to increase the air volume flowing from the compressor per unit of time. In this context, it is known from document WO 2009/146866 A1 to supply air precompressed by a turbocharger or ambient air to the compressor, said air being fed to the compressor in a manner in which the turbocharger is bypassed. 
     The object of the present invention is to provide a possibility that is as reliable, simple and cost-effective as possible for selectively feeding ambient air or precompressed air to a compressor of a vehicle. 
     This and other objects are achieved in accordance with the invention by a valve device for controlling the air intake for a compressor of a vehicle, wherein the valve device comprises a valve housing, which comprises a first compressed air inlet for connection to an ambient air feed, a second compressed air inlet for connection to a charge air feed, via which precompressed air can be fed, and a compressed air outlet for connection to the compressor. The valve device has a first switched state, in which the compressed air outlet is fluidically connected to the first compressed inlet, and has a second switched state, in which the compressed air outlet is fluidically connected to the second compressed air inlet. The valve device further comprises a switching device, which is capable of switching the valve device between the first switched state and the second switched state. The valve device can thus be switched in a simple manner between an intake of ambient air and an intake of charge air to the compressor. 
     The valve device can be provided, in particular, for use in a compressor system of a vehicle. Besides two compressed air inlets, the valve device may, in particular, have only one outlet for connection to the compressor. The switching device or the valve device can be electrically or pneumatically actuated in order to switch between switched states. It is contemplated for a sensor device to be connectable or connected in the region of the compressed air outlet, in the compressed air outlet, or downstream of the compressed air outlet. In particular, the sensor device may include a pressure sensor and/or a flow sensor. It is expedient if the sensor device or its sensors are connected to an electronic control device. It is also contemplated to form or to consider the sensor device as part of the valve device and/or as part of a compressor system. The sensor device can be formed or connected to determine the switched state of the valve device and/or to detect and to transmit data for detection and/or control of the switched state. 
     The valve device may include an electronic control device and/or may be connected or connectable to an electronic control device. A control device of this type can be formed, in particular, to control and/or switch the valve device or the switching device between different switched states. The electronic control device of the valve device, for communication purposes, may be connected or connectable to at least one further, possibly superordinate, control device of the vehicle. In particular, the switching device can be formed for control by way of the control device. It is expedient if a sensor device, for signal transmission, is connected to a corresponding control device. 
     The valve device can be formed in such a way that, in each switched state, it provides a fluidic connection of its single outlet, specifically the compressed air outlet, to at least one of the compressed air inlets. In particular, it may be that the fluid line between the first compressed air inlet and the compressed air outlet and the fluid line between the second compressed air inlet and the compressed air outlet are not shut off simultaneously in any switched state of the valve device. 
     As a result of the switching device, a fluid line between the second compressed air inlet and the compressed air outlet can be closed in the first switched state and/or a fluid line between the first compressed air inlet and the compressed air outlet can be closed in the second switched state. In the first switched state, only compressed air is therefore forwarded via the first compressed air inlet to the compressed air outlet and ultimately to the compressor, whereas an intake of compressed air via the second compressed air inlet is prevented. Conversely, in the second switched state, only an intake of compressed air via the second compressed air inlet is possible. 
     The valve device may have at least one third switched state, in which the first compressed air inlet and the second compressed air inlet are fluidically connected to the compressed air outlet. Fed air can thus be mixed. If, for example, compressed air having a pressure critical for the compressor is fed via the charge air feed, the pressure can thus be lowered by an intake of ambient air or by releasing precompressed air via the first compressed air inlet. On the one hand, the compressor can thus be preserved. On the other hand, it is not necessary to intervene in the turbocharger system in order to reduce the charge air pressure, which reduces the circuit complexity for the vehicle. 
     In particular, the valve device may have a series of different switched states, in which the first compressed air inlet and the second compressed air inlet are fluidically connected to the compressed air outlet. The switched states may differ with regard to the cross-sections of the first compressed air inlet and of the second compressed air inlet released in the valve device and/or with regard to the ratio of the released cross-sections. Different mixing ratios can thus be adjusted. It may be expedient if the switched state of the valve device between the first switched state and the second switched state can be adjusted substantially continuously. The valve device may therefore have further intermediate switched states between the first switched state and the second switched state. Here, it may be expedient if a sensor for detecting the pressure level of the fed air is arranged in the ambient air feed and/or in the charge air feed. The sensors can be connected directly or indirectly via further electronic components to the electronic controller of the switching device or of the valve device. An electronic controller may be embodied in such a way that it sets a switched state of the valve device, in which air guided via the compressed air outlet to the compressor does not exceed a predetermined pressure threshold value. A control process of this type can be implemented, for example, based on the sensor signals and can be achieved by switching between switched states. 
     The switching device of the valve device may have a piston, which is movable between a first position corresponding to the first switched state, in which it releases a fluidic connection between the first compressed air inlet and the compressed air outlet, and a second position corresponding to the second switched state, in which it releases a fluidic connection between the second compressed air inlet and the compressed air outlet. The piston can be received within the valve housing, in particular in a channel for guiding the piston. It is contemplated for the piston to have a seal, which for example to provide a seal between the piston and the elements of the valve housing or of the valve device in which it moves, for example the channel. It is thus easy to switch in particular between the first switched state and the second switched state. 
     The valve housing may have a first valve seat, which is assigned to the first compressed air inlet, and a second valve seat, which is assigned to the second compressed air inlet. It may be possible to bring a piston of the switching device controllably into bearing contact with the first valve seat and controllably into bearing contact with the second valve seat. In the first switched state, the piston is in bearing contact with the second valve seat and closes the fluid line between the second compressed air inlet and the compressed air outlet. In the second switched state, the piston is in bearing contact with the first valve seat and closes the fluid line between the first compressed air inlet and the compressed air outlet. This construction provides an accurately defined movement space for the piston. In the region of at least one valve seat, a sensor, for example a contact sensor, may be provided for example for localization of the piston. Such a sensor can be connected to a control device. A valve seat can be formed, for example, as an opening assigning a constriction in a corresponding compressed air inlet or a line portion. In particular, the piston can be movable back and forth between a position in which it is in bearing contact with the first valve seat and a position in which it is in bearing contact with the second valve seat. Here, it is contemplated for intermediate switched states to be established. 
     The switching device may have a switching disk, which is rotatable between a first position corresponding to the first switched state, in which it releases a fluidic connection between the first compressed air inlet and the compressed air outlet, and a second position corresponding to the second switched state, in which it releases a fluidic connection between the second compressed air inlet and the compressed air outlet. This is a further possibility for providing a reliable switching device that is to be switched easily. 
     In a further development, the switching device also includes an outlet disk with an outlet opening, via which a fluidic connection from the switching disk to the compressed air outlet can be produced or established, and also an inlet disk with a first inlet opening, via which a fluidic connection from the first compressed air inlet to the switching disk can be produced or established, and with a second inlet opening, via which a fluidic connection from the second compressed air inlet to the switching disk can be produced or established. The switching disk is arranged rotatably between the outlet disk and the inlet disk and forms a switching opening. Furthermore, the switching disk may be rotatable between a first position, in which a fluidic connection exists between the outlet opening and the first inlet opening via the switching opening in the switching disk, and a second position, in which a fluidic connection exists between the outlet opening and the second inlet opening via the switching opening. A simple switching device can thus be produced, with which the rotation of the switching disk is hardly stressed by compressed air from one of the compressed air inlets, since the switching disk is rotatable orthogonal to the airflow. The first position corresponds to the first switched position, and the second position corresponds to the second switched position. The switching disk may cover the second inlet opening in the first position and may cover the first inlet opening in the second position in such a way that it shuts off a fluid line through the corresponding openings. In this variant also, intermediate switched states are of course possible, in which a defined mixing of compressed air fed from both compressed air inlets is possible, as mentioned above. The outlet disk and/or the inlet disk can be mounted within the valve housing such that they are stationary with respect to the housing. 
     It is contemplated for the switching device to include an electric motor as an actuation device for switching between switched states. The switching device may also be connected to a separate actuation device, such as a motor of this type. An electromagnet and/or a spring device can also be used as an actuation device. The actuation device can be actuated by one of the above-described control devices. 
     The valve device can be formed in particular as a 3/2 valve. No unnecessary inlets and outlets are thus provided, which facilitates construction and control. 
     The present invention also relates to a compressor system comprising a valve device for controlling an air intake for a compressor as described above. Depending on the design of the valve device, advantages substantially identical to those already discussed are provided for the compressor system. The compressor system may include an ambient air feed and a charge air feed. 
     The compressor system may include a shut-off valve, which is connected between the compressed air outlet of the valve device and the compressor, and which is capable of shutting off or releasing the intake of compressed air from the valve device to the compressor. In particular, the shut-off valve may be capable of shutting off an intake of compressed air between the compressed air outlet and the compressor in a shut-off position and of enabling an intake of compressed air between the compressed air outlet and the compressor in a conducting position. An undesired intake of compressed air to the compressor can thus be prevented in a simple manner, for example when the compressor is operated in an idle phase. The compressor may alternatively or additionally also be coupled to a compressor coupling, via which it can be uncoupled from a drive. 
     The compressor system may expediently include an electronic control device, which is suitable for controlling the valve device. The control device can be connected directly to the valve device or to the switching device. It is contemplated for the control device of the compressor system to be connected to a control device of the valve device. The compressor system may include a sensor device connected between the compressed air outlet of the valve device and the compressor. The sensor device may in particular comprise a pressure sensor and/or a flow sensor. The sensor device or its sensors can be connected to an electronic control device. It is contemplated for the sensor device to be formed or connected to determine the switched state of the valve device and/or, for detection and/or control of the switched state, to detect data and to transmit the data to a control device, which may be a control device of the compressor system and/or part of an on-board electronic system. A control device of this type may, in particular, be formed to control and/or switch the valve device or the switching device between different switched states. It is expedient if the sensor device, for signal transmission, is connected to a corresponding control device. The control device may be connected to a CAN bus of the vehicle. 
     The invention also relates to a method for controlling an air intake for a compressor of a compressor system, as is described herein, wherein, for the air intake, the compressor is connected to the compressed air outlet of the valve device. The method includes the following step of controlling the valve device in such a way that the valve device switches between two switched states. The control can be implemented based on sensor signals of the sensor devices or sensors described herein. During the control process, vehicle parameters such as the vehicle speed, engine parameters such as the engine speed, and/or compressor parameters such as the compressor speed can be taken into consideration. 
     In accordance with a further development, the valve device is controlled such that it switches between the first switched state and the second switched state. 
     The valve device may also be controlled such that it is switched to or from a third switched state, in which the first compressed air inlet and the second compressed air inlet are fluidically connected to the compressed air outlet. 
     Within the scope of this description, a vehicle may be any type of motor vehicle. In particular, a vehicle may be a commercial vehicle, a mobile construction machine, a rail vehicle, a tractor or a lorry. A compressor system may comprise a compressor. A compressor or a compressor system may comprise a compressor coupling. A compressor system may comprise components for compressed air intake, lines, valves, compressed air connections and/or similar components. Components for controlling compressed airflows, for controlling the compressor or a compressor coupling may also be considered as parts of a compressor system. A compressed air preparation device comprising an air drier, a multi-circuit protection valve and further components can be considered a compressor system or may comprise a compressor system. A control process can be carried out electronically, electrically or pneumatically. A combination of electronic and pneumatic control may also be provided. A compressor system may, in particular, comprise one or more electronic control devices. 
     An electronic control device may be provided for example to control the compressor and/or the compressor coupling and/or a valve device, in particular to control one of the above-described valve devices, and/or may be accordingly connected. A control device may carry out a control process based on signals from one or more pressure sensors. It is particularly expedient if the control process is carried out based on signals transmitted from the sensor device arranged downstream of the valve device and/or is based on signals from the charge air feed and/or the ambient air feed. A control process may be carried out under consideration of vehicle parameters such as a vehicle speed, engine parameters such as an engine speed, and/or compressor parameters such as a compressor speed. Here, it may be expedient to transmit corresponding parameters via an on-board electronic system, for example a CAN bus, to the control device, which carries out the control process. 
     A charge air feed is used for the intake of precompressed air for a compressor. The air can be precompressed by a turbocharger or by another suitable device. An ambient air feed is used for the intake of ambient air, which is not precompressed. The ambient air may therefore be at atmospheric pressure. The shut-off of a fluid line can be interpreted as the closing of any direct or indirect fluidic connection. Two components, between which a fluid line is shut off, expediently cannot exchange any fluid, in particular any compressed air. A fluid, in particular air or compressed air, can flow between fluidically connected devices, such as a compressed air inlet and a compressed air outlet. 
     One or more openings and/or line portions and/or pressure chambers can be assigned to a compressed air inlet or compressed air outlet of a valve housing. An inlet or outlet can therefore be understood as an inlet region or outlet region, provided compressed air flows in substantially just at one opening point and flows out again from the region substantially only at one opening point. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a vehicle comprising a compressor system; 
         FIG. 2  is a schematic illustration of a variant of a valve device; 
         FIG. 3  is a schematic illustration of a further variant of a valve device; 
         FIGS. 4 a  and 4 b    show different schematic views of yet a further variant of a valve device; 
         FIGS. 5 a  to 5 d    show different schematic views of yet a further variant of a valve device; and 
         FIG. 6  is a schematic illustration of a valve device with further components. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In the following description of the figures, like reference signs denote like or functionally similar components. In  FIG. 1 , pneumatic lines are illustrated as solid lines, whereas electrical lines and connections are illustrated in a dashed manner. 
       FIG. 1  shows a schematically illustrated commercial vehicle  10 . Besides a drive motor  14  and a compressor system  12 , the illustrated commercial vehicle  10  includes a compressed air preparation system with consumers  16 , an air filter  18 , a charge air cooler  20 , and a turbocharger  22 . Besides a compressor  24 , which may be a single-cylinder or a two-cylinder compressor, the compressor system  12  itself includes an electronic control device  26  with a connection  28  to a CAN bus  30 . An ambient air feed  32  and a charge air feed  34  are provided. A first pressure sensor  36  is provided in the ambient air feed  32 , and a second pressure sensor  38  is provided in the charge air feed  34 . Instead of the pressure sensors  36 ,  38 , flow sensors or other suitable sensor devices, for example comprising a pressure sensor and a flow sensor, can be provided. The ambient air feed  32  guides air from the ambient environment directly behind the air filter  18  to an air intake valve device  40 . The charge air feed guides precompressed air, also referred to as charge air, which is precompressed by the turbocharger  22  and then cooled in the charge air cooler  20 , likewise to the air intake valve device  40 . The air intake valve device  40  is connected to the compressor  24  in order to feed thereto air for compression. A sensor device  39  is connected between the compressor  24  and an outlet, connected thereto, of the air intake valve device  40 . The sensor device  39  includes a pressure sensor and a flow sensor. The valve device  40  preferably comprises just one single compressed air outlet for connection to the compressor  24  or for the intake of air to the compressor  24 . 
     Depending on the switched state of the valve device  40 , the compressor  24  draws in air, which has already been precompressed by the turbocharger  22 , via the charge air feed  34  or draws in ambient air, which is not precompressed, via the ambient air feed  32 . If the valve device  40  is in its illustrated first switched state, the compressor  24  thus draws in ambient air via the air filter  18  and the ambient air feed  32 . In the second switched state (not illustrated), the compressor  24  draws in air, which has already been precompressed by the turbocharger  22 , via the air filter  18 , the turbocharger  22 , the charge air cooler  20  and the charge air feed  34 . Due to the increased charge pressure compared to the ambient pressure, the air volume conveyed by the compressor  24  per unit of time increases here with constant rotational speed of the compressor  24 . 
     The turbocharger  22  is driven by the exhaust gases of the drive motor  14 , wherein the primary task of the turbocharger  22  is to be considered a charging of the drive motor  14 , that is to say that six illustrated cylinders  42  of the drive motor  14  are operated with a greater amount of combustion air. 
     The compressor  24  is driven by the drive motor  14  in a manner known by a person skilled in the art. For example, the compressor  24  can be driven by the drive motor  14  via a geared drive. The compressed air conveyed by the compressor  24  is fed to the compressed air preparation system with consumers  16 . The compressed air preparation system with consumers  16 , in particular, includes a compressed air preparation system known to a person skilled in the art and also a plurality of consumer circuits, which for example are protected from one another by means of a multi-circuit protection valve and which are connected to the individual consumers. The compressor  24  also has a dead space  46 , measuring approximately 10 ccm per cylinder and connectable by a valve device  44  in order to attenuate pressure peaks during the compressed air conveyance. A dead space  46  is generally understood to be any space connected to a piston chamber of the compressor, said space remaining empty at the end of a compression stroke of the compressor. The connection of a dead space  46  therefore lowers the possible maximum compression of the compressor and therefore lowers the pressure peaks during a compression stroke. 
     A shut-off valve  48  can be arranged between the compressor  24  and the air intake valve device  40 , and an air intake from the air intake valve device  40  to the compressor  24  can be shut off or opened via said shut-off valve. The compressor  24  then, when the shut-off valve is closed, cannot draw in any air and consequently also can no longer convey compressed air. It is known that, in this state, oil, which is used conventionally for lubrication of the compressor  24 , is drawn into the compression chamber by the negative pressure produced during an expansion stroke of the compressor  24  and is ejected during the next compression stroke of the compressor  24  in the direction of the connected compressed air preparation system with consumers  16 . In order to prevent this, it is contemplated for the shut-off valve  48  not to be completely sealed, but to have a defined residual leak in order to limit the intake negative pressure of the compressor  24 . The oil ejection of the compressor  24  is thus reduced. The shut-off of the air intake to the compressor  24  by use of the shut-off valve is a simple possibility for transferring the compressor  24  into an energy-saving operating mode. Alternatively or additionally, the compressor  24  can be coupled to its drive via a coupling apparatus. By releasing the coupling, the compressor  24  can be transferred into an energy-saving operating mode. 
     If the charge pressure provided by the turbocharger  22  is below an adjustable charge pressure threshold, the air intake valve device  40  is in its second switched state (not illustrated). The compressor  24  then receives air, which has already been precompressed, via the charge air feed  34 . The compressor  24  is optimized for the intake of air that has not been precompressed, as a result of which low charge pressures considerably increase the air volume conveyed therefrom. Up to a charge pressure of approximately 0.6 bar, the compressor  24  optimized for the intake of air that has not been precompressed can also without difficulty convey air that has already been precompressed. If the charge pressure provided by the turbocharger  22  exceeds this first limit, which is also referred to as a dead space charge pressure threshold, the dead space  46  associated with the compressor  24  is thus connected via the valve device  44  in order to lower the conveying pressures occurring during the conveyance of the air that has already been compressed. If the charge pressure provided by the turbocharger  22  rises further and ultimately exceeds a further limit referred to as a charge pressure threshold, the conveying pressures occurring can thus damage the compressor  24  in spite of the dead space  46 . If the charge pressure threshold is exceeded, the air intake valve device  40  is therefore transferred into its illustrated first switched state. The dead space  46  associated with the compressor  24  can be closed again by actuation of the valve device  44 . The compressor  24  optimized for the intake of air that has not been precompressed now, via the ambient air feed  32 , draws in air that has not been precompressed. The connection of the dead space  46  can also otherwise be used to reduce the conveyed air volume or to save energy if a large quantity of air is not required. The valve device  44  can be controlled or actuated for example via the control device  26 . 
     The air intake valve device  40  is an electrically or pneumatically actuatable valve device, which in particular releases a maximum flow cross section of the air feeds  32 ,  34  depending on its switched state. The air intake valve device  40  can be connected to the electronic control device  26 , which can be formed to control the valve device in particular based on signals of the sensor device  39  and/or of the sensors  36 ,  38 . Control can also occur directly via one or more of the sensors  36 ,  38 ,  39 , which then accordingly are connected to the air intake valve device  40 , wherein no further data are then required by an engine control device in order to switch the valve device  40 . The air intake valve device  40  can be controlled via the electronic control device  26  in accordance with the engine speed and/or the compressor speed and/or further engine parameters and/or vehicle parameters. The engine speed and other parameters can be read out preferably from an engine control device and/or another control device. In this case, the characteristic map of the engine turbocharger can be presumed as known. Corresponding data can be transmitted via the CAN bus  30 . 
       FIGS. 2 to 5  are schematic illustrations of different valve devices, which can each be used as an air intake valve device  40  for a compressor system. Each of these valve devices has a valve housing  100 . A first compressed air inlet  102 , a second compressed air inlet  104  and a single compressed air outlet  106  are provided on the valve housing. Expediently, the first compressed air inlet  102  is provided for connection to an ambient air feed, and the second compressed air inlet  104  is provided for connection to a charge air feed. The compressed air outlet  106  is provided for the intake of compressed air from at least one of the compressed air inlets  102 ,  104  to a compressor. 
     The valve devices each have at least one first switched state, in which the compressed air outlet  106  is fluidically connected to the first compressed air inlet  102 , and a second switched state, in which the compressed air outlet  106  is fluidically connected to the second compressed air inlet  104 . A switching device is also provided in order to switch the valve device between different switched states. The switching device in each case comprises an actuation device  108 , which is controllable via an electrical control line  110 . The control line  110  can be connected for example to a control device  26  and/or to one or more sensor devices. The actuation device  108  may have a shaft or a rod  109  for power transmission. It is contemplated for the actuation device  108  to be formed as an electric motor or an electromagnet. The actuation device  108  can be controllable in such a way that it sets a multiplicity of switched states of the valve device. In particular, intermediate switched states, in which both the first compressed air inlet  102  and also the second compressed air inlet  104  are simultaneously connected to the compressed air outlet  106 , are thus possible. In these intermediate switched states, there is thus a different mixture of the fed air, or it is possible for compressed air coming from the charge air feed  34  to escape via the ambient air feed  32  in varying extents due to differently set flow cross sections. The intermediate switched states can be controlled continuously. 
     In the case of the valve device shown in  FIG. 2 , the switching device includes a piston  112 , which is movable within the housing  100  by way of the actuation device  108 . In the valve housing  100 , a first valve seat  114  is provided and is assigned to the first compressed air inlet  102 . A second valve seat  116  is assigned to the second compressed air inlet  104 . The valve seats  114 ,  116  form a respective stop for the piston  112 , of which the movement is therefore limited to the region between the valve seats  114 ,  116 . If the piston  112  bears against the first valve seat  114 , it closes the fluid connection between the compressed air outlet  106  and the first compressed air inlet  102 . A fluidic connection is present between the second compressed air inlet  104  and the compressed air outlet  106 , and air can thus flow there. This position of the piston corresponds to the second switched state of the valve device. If, on the other hand, the piston  112  bears against the second valve seat  116 , as is shown in  FIG. 2 , it closes the fluid connection between the compressed air outlet  106  and the second compressed air inlet  104 . A fluidic connection is present between the first compressed air inlet  102  and the compressed air outlet  106 , and air can thus flow there. This position of the piston  112  corresponds to the first switched state of the valve device. Intermediate switched states can be set by positioning the piston in a position between the valve seats  114 ,  116 . 
       FIG. 3  shows a variant of a valve device, in which the switching device includes a piston  122 , which is movable by way of the actuation device  108 . The piston  122  comprises a seal  124 , which is used to provide a seal with respect to the valve housing  100 . In this variant, no valve seats limiting a movement of the piston  122  are provided. Rather, the piston  122  is received in a channel  126  and can be moved therein. At one end of the channel  126 , the piston can penetrate at least partially into the first compressed air inlet  102  or into an assigned line in order to block a fluid connection between the first compressed air inlet  102  and the compressed air outlet  106 . Air can flow between the second compressed air inlet  104  and the compressed air outlet  106 . This position corresponds to the second switched state. The piston  122 , as shown in  FIG. 3 , can also be moved into a position between the second compressed air inlet  104  and the compressed air outlet  106  in such a way that it blocks a fluid connection between the second compressed air inlet  104  and the compressed air outlet  106 . Air can flow between the first compressed air inlet  102  and the compressed air outlet  106 . This position corresponds to the first switched state. In this variant, the compressed air outlet  106  and the second compressed air inlet  104  divert from the channel  126  at right angles to the direction of movement of the piston  122 , whereas the first compressed air inlet  102  can receive the piston  122  in the direction of movement. The channel  126  in the housing  100  has a cavity, in which the piston  122  can be received in order to completely release both compressed air inlets  102 ,  104 . The maximum cross section can thus be released for both air feeds. 
       FIGS. 4 a  and 4 b    show different sectional views of a further variant of a valve device. In this example, the switching device comprises a switching disk  132  that is rotatable by way of an actuation device  108 . The switching disk  132  is mounted rotatably on a shaft  109  of the actuation device  108  and has a seal  134 . The valve housing  100  is formed in such a way that the switching disk  132  can rotate within the housing  100  in such a way that there is sealing contact between the housing wall and seal  134  of the switching disk  132 , at least in certain positions. In  FIG. 4 a   , a corresponding position is shown in which the switching disk  132  closes a fluid connection between the first compressed air inlet  102  and the compressed air outlet  106 . A fluidic connection is present between the second compressed air inlet  104  and the compressed air outlet  106 .  FIG. 4 a    therefore shows the second switched state. By rotating the switching disk  132 , the switched state can be changed. It goes without saying that intermediate switched states can be adopted and are defined by a suitable rotational position of the switching disk  132 .  FIG. 4 b    shows a side view, in which the actuation device  108  and the shaft  109  can be seen. 
       FIGS. 5 a  to 5 d    show a further variant of the valve device, in which the switching device comprises a switching disk  142  with a slitted opening  144 , which is shown in  FIG. 5 c   . The switching disk  142  is arranged rotatably on the shaft  109  of the actuation device  108 . The switching device further comprises an outlet disk  152  mounted in the valve housing  100  and an inlet disk  162  mounted in the valve housing  100 . The switching disk  142  is arranged between the inlet disk  162  and the outlet disk  152  and is rotatable relative thereto. A first flat side of the inlet disk  162  and a first flat side of the outlet disk  152  each face a flat side of the switching disk  142  and expediently bear thereagainst in an airtight manner. The second flat face of the outlet disk  152  faces a pressure chamber  154  connected to the compressed air outlet  106 . The outlet disk  152  comprises an opening slit  156 , which can be seen in  FIG. 5 b    and by which a fluid connection from the switching disk  142  to the compressed air outlet  106  can be produced. As can be seen in  FIG. 5 d   , the inlet disk  162  comprises a first inlet slit  164 , via which a fluid connection to the first compressed inlet  102  can be produced. The inlet disk  162  further comprises a second inlet slit  166 , via which a fluid connection to the second compressed air inlet  104  can be produced. The disks additionally have structures making it possible for the shaft  109  to be received in such a way that the switching disk  142  can rotate between the two other disks. By rotating the switching disk  142 , the slitted opening  144  therein is also rotated. The openings of the switching disk  142  and the inlet disk  162  are dimensioned in such a way that the switching disk completely covers the second inlet slit  166  in the inlet disk  162 , at least in a first position, and therefore blocks the fluid connection to the second compressed air inlet  104  via the inlet disk  162 . In this position, the slitted opening  144  in the switching disk  142  and the first inlet slit  164  overlie one another in such a way that the opening slit  156  in the outlet disk  152 , the opening  144  in the switching disk  142 , and the opening in the first inlet slit  164  overlie one another at least in part. Compressed air can thus flow from the first compressed air inlet  102  to the compressed air outlet  106  through these openings or slits, whereas a fluid connection between the second compressed air inlet  104  and the compressed air outlet  106  is blocked. This corresponds to the first switched state. Similarly, the switching disk  142  can be rotated in such a way that the first inlet slit  164  is covered by the switching disk  142 , and a fluidic connection is produced between the compressed air outlet  106  and the second compressed air inlet  104  via the openings  144 ,  156  and  166 . This position of the switching disk  142  corresponds to the second switched state. By rotating the switching disk  142  into a position in which the slitted opening  144  partially overlies the first inlet opening  164  and the second inlet opening  166  and also the opening  156  in the outlet disk  152 , intermediate switched states can be set, in which both compressed air inlets are fluidically connected to the compressed air outlet  106 . 
     The inlet disk  162 , the outlet disk  152  and/or the switching disk  142  can consist of ceramic material. It is also contemplated for sealing devices for sealing between the disks or between the outlet disk  152  and the compressed air outlet  106  and/or between the inlet disk and the compressed air inlets to be provided in order to prevent compressed air from flowing undesirably past the openings in the disks. 
       FIG. 6  is a schematic partial view of a valve device  40  with further components. In this example, a valve device as shown in  FIG. 2  can be seen. It goes without saying that any other of the above-described valve devices can be used in conjunction with  FIG. 6 . The actuation device  108  of the valve device  40  is connected via a control line  110  to an electronic control device  170 , which can be an electronic control unit  26  as described with reference to  FIG. 1 . It is also contemplated for the control device  170  to be an independent control device, which for example can communicate with a control unit  26  of a compressor system or with an on-board computer system of the vehicle. 
     A sensor device  39  is provided downstream of the compressed air outlet  106  of the valve device  40 . The sensor device  39  in this example comprises a pressure sensor  172  and a flow sensor  174 . It is also contemplated for the sensor device  39  to have only one of the two sensors  172 ,  174  or to also have additional sensors. The sensor device  39  or the sensors  172 ,  174  are connected to the control device  170  for the purpose of signal transmission. The control device  170  is also connected via a signal connection  176  to one or more components, such as a control unit of the compressor unit or further devices of the on-board electronic system, for example via a CAN bus. Based on the signals of the sensor device  39  and/or signals provided by the signal line  176 , which for example may represent engine parameters such as engine speed, compressor parameters such as compressor speed, or further vehicle parameters such as vehicle speed, the position of the valve device  40  or its switched state can be determined and controlled. The control process can be carried out, for example, by the control device  170 . 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               10  commercial vehicle 
               12  compressor system 
               14  engine 
               16  compressed air preparation system with consumers 
               18  air filter 
               20  charge air cooler 
               22  turbocharger 
               24  compressor 
               26  control device 
               28  connection 
               30  CAN bus 
               32  ambient air feed 
               34  charge air feed 
               36  pressure sensor 
               38  pressure sensor 
               39  sensor device 
               40  air intake valve device 
               42  engine cylinder 
               44  valve device 
               46  dead space 
               48  shut-off valve 
               100  valve housing 
               102  compressed air inlet 
               104  compressed air inlet 
               106  compressed air outlet 
               108  actuation device 
               109  shaft/rod 
               110  control line 
               112  piston 
               114  valve seat 
               116  valve seat 
               122  piston 
               124  seal 
               126  channel 
               132  switching disk 
               134  seal 
               142  switching disk 
               144  opening 
               152  outlet disk 
               154  pressure chamber 
               156  opening slit 
               162  inlet disk 
               164  inlet slit 
               166  inlet slit 
               170  control device 
               172  pressure sensor 
               174  flow sensor 
           
         
       
    
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.