Abstract:
A vehicle seat having a device for controlling a pneumatic suspension system, by means of which the vehicle seat is spring-mounted relative to a vehicle body part, including at least one directional-control valve which is pneumatically connected to the device for controlling the suspension system and which is arranged in the region of a seat part of the vehicle seat, the seat part being movable relative to a base frame and which is adjustable by a movement of the seat part relative to the base frame.

Description:
PRIORITY CLAIM 
     This application claims the benefit of German Application Serial No. 10 2008 022 045.0 filed May 3, 2008, contents of which are incorporated herein. 
     FIELD OF THE INVENTION 
     The invention relates to a pneumatic suspension system and, more specifically, to a control device configured to control a pneumatic suspension system of a vehicle seat spring-mounted to a vehicle body part. 
     BACKGROUND OF THE INVENTION 
     It is known to equip vehicle seats with a pneumatic suspension system which includes, among other things, at least one air spring and a control device which carries out an automatic level adjustment as a function of the weight loading a seat part of the vehicle seat. By way of example, when the seat is occupied by a driver of substantial weight, more air pressure is introduced into an air spring arranged within a base frame below the seat part. This typically produces the desired suspension effect with equal spring travel both in the upward and downward direction. By contrast, if the seat is occupied by a person of relatively insubstantial weight, air is discharged from the air spring within the suspension system in order to avoid too high an arrangement of the seat for this person and thus too short a spring travel in the upward direction. 
     Such suspension systems often cannot distinguish between the state of an occupied seat and the state of an unoccupied seat. As a result, the unoccupied seat state leads to the situation in which previous vehicle seats are set to a level as a function of their weight, which is primarily determined by the seat part, a backrest and parts of the base frame. Such a leveling of the vehicle seat has the result that, following previous seat occupancy, in the state of seat non-occupancy substantial air is unnecessarily discharged from the suspension system in order to obtain such a setting as a function of the intrinsic weight of the seat. This leads to an unnecessary waste of the air present in the suspension system and in particular in the air spring, which must be re-introduced, for example by means of a compressor. 
     Accordingly, there is a need for a control device configured to control a pneumatic suspension system of a vehicle seat spring-mounted to a vehicle body part in which the air discharged from the suspension system is controlled as a function of seat occupancy. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a vehicle seat having a control device for controlling a pneumatic suspension system. The preferred embodiment includes a vehicle seat that is spring-mounted relative to a vehicle body part the vehicle seat having a seat part being movable relative to a base frame. The present invention includes a control device that is pneumatically connected to at least one directional-control valve for controlling the suspension system and which is arranged in the region of the seat part of the vehicle seat. Due to such a direct interaction between the directional-control valve, which for example may be a 2/2-way valve and a 3/2-way valve, and the seat part of the vehicle seat, the present invention detects whether the seat part is or is not being loaded by weight due to the person sitting thereon on the basis of the movement of the seat part. 
     As a function of the detected seat occupancy, an air discharge line of the suspension system, which conveys discharged air, is closed or opened so that, in the event of the seat being unoccupied while the directional-control valve is in the closed state, the air quantity present during the seat occupancy remains within the suspension system. As a result, not only is no air discharged unnecessarily from the suspension system, but when the seat which is not occupied is occupied again, a desired level setting of the vehicle seat can take place more quickly, without having to wait a relatively long time for the desired air pressure to build up within the suspension system. The directional-control valve is preferably arranged in the air discharge line of the pneumatic suspension system in order to control a discharged air flow of the suspension system. In the preferred embodiment, the control has two states, namely, the closed state and the open state of the directional-control valve and thus of the air discharge line. Typically the closed state exists when the seat is not occupied, whereas the open state exists when the seat is being occupied. 
     The directional-control valve is in the open state after a downward movement of the seat part brought about as a result of seat occupancy, whereas it is in the closed state after an upward movement of the seat part brought about as a result of seat non-occupancy. 
     In a preferred embodiment, the directional-control valve has a retractable and extendable slide, the open end of which is below a lower edge of the seat part in the closed state of the directional-control valve and makes contact with a side face of the seat part in the open state of the directional-control valve. The slide is preferably configured to retract into and extend out of the directional-control valve by an upward or downward pivoting of the front section of the seat part so that a closed or an open state of the slide and thus of the air discharge line is obtained. 
     In a further embodiment, the vehicle seat has at least one spring between an underside of the seat part and the base frame arranged therebelow. The spring preferable has a spring force which can be dimensioned in such a way that the seat part with its intrinsic weight brings about no movement of the spring and therefore no movement of the slide of the directional-control valve. However, for example, if the seat part with its intrinsic weight is additionally occupied by a predefinable weight of a person, the spring is moved or compressed and thus the slide of the directional-control valve is displaced, which leads to an opening of the directional-control valve. 
     The directional-control valve is preferably connected via the air discharge line to at least one air spring for the suspension of the vehicle seat. 
     According to one alternative embodiment, at least one second directional-control valve for closing or opening the air discharge line may be arranged between the directional-control valve and the air spring. In yet an alternative embodiment, the air spring is connected to an air supply line and to a third directional-control valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages and expedient features can be found in the following description in conjunction with the drawing, in which: 
         FIG. 1  shows, in a schematic side view, a vehicle seat according to one preferred embodiment of the invention in the unoccupied state; 
         FIG. 2  shows, in a schematic side view, the vehicle seat of  FIG. 1  in the state of seat occupancy, and 
         FIG. 3  shows, in an overview, different switching states of a device for controlling a pneumatic suspension system comprising a directional-control valve for the vehicle seat according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows, in a schematic side view, a vehicle seat according to one preferred embodiment of the invention in the unoccupied state, i.e. without a seat part being occupied by a person. The vehicle seat comprises a backrest  1  and a seat part  2 . Arranged below the seat part  2  is a base frame  3  which is essentially composed of an upper component  4 , a lower component  5  and scissors arms  6 ,  7  which are connected to one another in a scissors-like manner and which are joined to one another in a pivoting manner at a pivot point  8 . 
     The scissors frame comprising the scissors arms  6 ,  7  can be extended to a greater or lesser degree resulting in a height adjustment of the vehicle seat by displacing the scissors arms using rollers  9 ,  10  in the longitudinal direction of the vehicle seat. Preferably the ends of the scissors arms  6 ,  7  opposite the rollers  9 ,  10  have fixed bearings  11 ,  12  which are arranged on the upper component  4  and on the lower component  5 , respectively. 
     In the preferred embodiment, at least one of the scissors arms  6  is connected to an air spring  13 , the air pressure of which determines the height extension of the scissors arms  6 ,  7 , as well as of the base frame  3  as a whole. The seat part  2  is moved upwards in its front region with respect to the upper component  4  by means of a schematically shown spring  14 . 
     According to one embodiment of the invention, a 2/2-way valve  15  is provided having a slide  16  that can be retracted or extended in the direction of the double arrow  17 . When the seat is not occupied, a front end  16   a  of the slide  16  is located below a lower edge of the seat part  2  and is thus extended. As explained below, alternative valves  15  may be used consistent with the scope of the present invention. 
       FIG. 2  shows the vehicle seat of  FIG. 1  in the state of seat occupancy. Components which are identical and which have the same function are provided with the same references. The vehicle seat shown in  FIG. 2  is acted upon on the upper side by a weight load  2   a  which is intended to illustrate seat occupancy. As a result of the downward-acting weight force of the weight load  2   a , the seat part  2  moves in the downward direction, as shown by an arrow  2   b . As a result, the slide  16  is displaced out of its position below the seat part and retracts into the directional-control valve in the direction of the arrow  17 . An air discharge line  18  coming from the device  20  for controlling the pneumatic suspension system is opened by the directional-control valve  15 , allowing discharged air to escape via the air discharge line  18  and, in an alternative embodiment, via a further air discharge line  19  which is connected to the air spring  13 . 
     By contrast, when the seat is not occupied, as in the state of the vehicle seat shown in  FIG. 1 , the air discharge line  18  is closed by the directional-control valve  15 , thereby by restricting the discharge of air from the suspension system. 
     Describing alternative embodiments,  FIG. 3  shows different switching states of the directional-control valve and of the device for controlling the pneumatic suspension system comprising a plurality of directional-control valves. 
     When there is seat non-occupancy  21  which is detected through the slide  16 , a directional-control valve  22 , which is integrated as an air valve secondarily in seat occupancy detection, is closed. As a result, a discharged air flow within an air discharge line  23 ,  25  is not given the opportunity to escape from the suspension system. 
     A second directional-control valve  24  is arranged within the device for controlling the pneumatic suspension system. Shown next to this is an air spring  26  having a certain air pressure. Leading to the air spring  26  are air supply lines  27 ,  29  which can be closed or opened by means of a 2/2-way valve  28  as the third directional-control valve or by means of a compressor. Reference  30  denotes a vehicle power connection for supplied air. 
     As shown with reference to the state  21 , a discharged air flow through the air discharge line  23  is blocked by the 3/2-way valve  22  being closed due to the position of an associated slide  26 . As a result, no discharged air can escape, even though the second directional-control valve  24  is in the open state. 
     In a state  31  of seat occupancy following previous seat occupancy by a person heavier than the current person, the seat is set too high for the new person of lesser weight due to the increased air pressure which was necessary for setting the air spring and the suspension system due to the heavier person. Accordingly, it is necessary to allow a certain quantity of air to escape as discharged air via an air discharge line  33 ,  35 . Since a directional-control valve  32  is automatically displaced into the open state as a result of the movement of the slide  16  during a downward movement of the seat part  2  caused by the seat occupancy, air can be discharged via the air discharge line  33 ,  35 . A second directional-control valve  34  is also in the open state. A third directional-control valve  38  is in the closed state in order to block an air supply line  37 ,  39  and the coupling of a power connection  40  to an air spring  36 . 
     A state  41  of seat occupancy which takes place after a previous seat occupancy in which a lighter person occupied the seat has the result that the seat is set too low for the person of greater weight now using the seat. Accordingly, a higher pressure is built up within the air spring  46 , which takes place through the air supply lines  47 ,  49  by means of an open third directional-control valve  48  and a power connection  50 . Air discharge lines  43 ,  53  are closed by means of a second directional-control valve  44 . A first directional-control valve  42  is in the open state since in the event of seat occupancy the slide  16  is pushed into the directional-control valve  15  and thus the directional-control valve is placed in an open state. 
     In a switching state  51 , seat occupancy after a previous leveling of the vehicle seat is shown. Once again, a directional-control valve  52  is in the open state due to the fact that the seat is occupied, with a second directional-control valve  54  being in the closed state. Air discharge lines are denoted by references  53 ,  55 . An air spring  56  is also shut off from any air supply by means of a directional-control valve  58 , air supply lines  57 ,  59  and also a power connection  60 . As a result, no significant escape of discharged air from the suspension system takes place. 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.