Patent Publication Number: US-2021178945-A1

Title: Vehicle seat having a suspension unit for cushioning rolling and vertical suspension movements

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of German Patent Application No. 102019134237.6 filed Dec. 13, 2019, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The invention relates to a vehicle seat having a suspension unit for cushioning the rolling and vertical movements of the vehicle seat, wherein the vehicle seat has a vehicle seat upper part and a vehicle seat lower part, wherein the vehicle seat upper part and the vehicle seat lower part are connected by means of the suspension unit so that the vehicle seat upper part and the vehicle seat lower part are movable relative to one another, wherein the suspension unit comprises a scissor arrangement having a first scissor arm and a second scissor arm. 
     BACKGROUND 
     Vehicle seats having roll and vertical suspensions are known from the prior art; for example, WO 2014/176130 A discloses a roll suspension which can cushion rolling movements of the vehicle or the vehicle seat. However, such a rolling movement, as shown in the prior art, is very complex in terms of design and requires many actively controlled components and is also very space-consuming. 
     SUMMARY 
     The object of the present invention is therefore to provide a vehicle seat having a suspension unit for cushioning rolling and vertical suspension movements, which is constructed in a simpler manner than that shown in the prior art. 
     The core idea of the present invention is to provide a vehicle seat having a suspension unit for cushioning the rolling and vertical movements of the vehicle seat, wherein the vehicle seat has a vehicle seat upper part and a vehicle seat lower part, wherein the vehicle seat upper part and the vehicle seat upper part are connected by means of the suspension unit so that the vehicle seat upper part and the vehicle seat lower part are movable relative to one another, wherein the suspension unit comprises a scissor arrangement having a first scissor arm and a second scissor arm, wherein the suspension unit is connected rotatably about a first axis of rotation to the vehicle seat lower part and comprises a spring element support and a first fluid spring element and a second fluid spring element, wherein the first fluid spring element and the second fluid spring element are each connected to the vehicle seat lower part and to the spring element support which is rotatably connected about a second axis of rotation to the first scissor arm and rotatably connected about a third axis of rotation to the second scissor arm, and wherein a fluid can be pumped between the first fluid spring element and the second fluid spring element by means of a pump unit, so that the vehicle seat upper part is substantially in a horizontal position. 
     Alternatively, the object is achieved by a vehicle seat having a suspension unit for cushioning the rolling and vertical movements of the vehicle seat, wherein the vehicle seat has a vehicle seat upper part and a vehicle seat lower part, wherein the vehicle seat upper part and the vehicle seat upper part are connected by means of the suspension unit so that the vehicle seat upper part and the vehicle seat lower part are movable relative to one another, wherein the suspension unit comprises a scissor arrangement having a first scissor arm and a second scissor arm, wherein the suspension unit is connected rotatably about a first axis of rotation to the vehicle seat lower part and comprises a spring element support and a first fluid spring element and a second fluid spring element, wherein the first fluid spring element and the second fluid spring element are each connected to the vehicle seat lower part and to the vehicle seat upper part which is rotatably connected about a second axis of rotation to the first scissor arm and rotatably connected about a third axis of rotation to the second scissor arm, and wherein a fluid can be pumped between the first fluid spring element and the second fluid spring element by means of a pump unit, so that the vehicle seat upper part is substantially in a horizontal position. 
     In this case, “rolling movement” is understood to mean a rotational movement of the vehicle seat about an axis of rotation which is arranged to run in the vehicle seat longitudinal direction. 
     The first axis of rotation is therefore particularly preferably arranged parallel to the first vehicle seat longitudinal direction. 
     According to a preferred embodiment, it is also provided that the vehicle seat upper part and the vehicle seat lower part can be cushioned relative to one another by means of the suspension unit. 
     According to a particularly preferred embodiment, the first fluid spring element the second fluid spring element is preferably a resiliently deformable air spring. 
     In particular, the first fluid spring element is arranged to run in the direction of the first angle and of the second angle, i.e. the first fluid spring element is arranged to run obliquely as seen in a standard coordinate system. 
     The standard coordinate system is formed from the vehicle seat longitudinal direction, the vehicle seat width direction and the vehicle seat height direction, which are each arranged at a right angle to one another. 
     Because, according to one embodiment, the first fluid spring element is connected to the spring element support and the vehicle seat lower part, it can be concluded that the first angle and the second angle are a function of the spring position of the vehicle seat. By means of a suspension movement, which can be a rolling and/or vertical suspension movement, the position of the spring element support changes in space, so that a first end of the first fluid spring element also changes its position in space, wherein a second end of the first fluid spring element, which is connected to the vehicle seat lower part, is not changed in its position. This means in particular that the first angle and the second angle are not constant during a suspension movement of the vehicle seat. In a neutral position, which means that the vehicle seat is not subject to any suspension movement, i.e. there is no relative movement of the vehicle seat upper part with respect to the vehicle seat lower part, the first angle and the second angle are constant. 
     Depending on the size of the first angle and the second angle, it is possible to adjust the spring stiffness of the first fluid spring element. The spring stiffness is in particular an adjustment option for the vertical direction and for the roll direction for the suspension movement. By setting the first angle and the second angle, it is possible to adjust the spring stiffness with regard to the vertical direction and the roll direction or the rolling spring direction. 
     It is particularly preferred that the first scissor arm and the second scissor arm intersect in a first region, viewed in the vehicle seat longitudinal direction, wherein provision is made that no structural connection is provided between the first scissor arm and the second scissor arm, with the exception of the spring element support. This means in particular that when the vehicle seat upper part moves with respect to the vehicle seat lower part, the first region, which represents the intersection region of the first scissor arm with the second scissor arm, must follow the movement of the vehicle seat. In particular, this means that there is no common axis of rotation between the first scissor arm and the second scissor arm. 
     It can be provided that the first scissor arm and the second scissor arm are force-connected, for example by a frictional force, if the scissor arms are in contact with one another. 
     The above-described forced guidance or forced movement of the spring element support due to the movement of the vehicle seat upper part relative to the vehicle seat lower part produces a spring force of the first fluid spring element and the second fluid spring element, so that cushioning of the vehicle seat is caused by the suspension unit. 
     According to an alternative embodiment, a structural connection is provided between the first scissor arm and the second scissor arm, so that the scissor arrangement is a scissor frame in the conventional sense, i.e. the scissor arms are rotatably connected to one another about a common axis of rotation. In this case, the spring element support is preferably fastened directly to the common axis of rotation. 
     Generally speaking, when the vehicle seat upper part moves relative to the vehicle seat lower part in a vertical direction, i.e. in the vehicle seat height direction, due to an external force acting on the vehicle seat, the rotatable arrangement of the spring element support on the first scissor arm or the second scissor arm causes a corresponding movement of the spring element support. This means that in the event of a vertical deflection, i.e. a deflection in the vehicle seat height direction, the spring element support experiences a linear displacement corresponding to the vehicle seat upper part in the vehicle seat height direction. In the event of a rolling movement of the vehicle seat, i.e. in the event of a rotation of the vehicle seat upper part relative to the vehicle seat lower part about the first axis of rotation, the spring element support is also subjected to such a rolling movement. The first fluid spring element and the second fluid spring element are deformed by the rolling movement of the spring element support, so that a spring force is produced which counteracts the rolling movement. 
     According to the invention, it is provided that the suspension unit comprises a second fluid spring element, wherein the second fluid spring element is connected on the one hand to the vehicle seat lower part and on the other hand to the spring element support, and wherein the second fluid spring element is arranged at a third angle to the vehicle seat width direction and arranged at a fourth angle to the vehicle seat height direction. 
     The second fluid spring element is particularly preferably arranged in such a way that, with respect to a plane formed from the vehicle seat longitudinal direction and the vehicle seat height direction, the first fluid spring element is arranged on a first side of the plane and the second fluid spring element is arranged on the second side of the plane. 
     It is also possible that the first angle corresponds to the third angle and the second angle corresponds to the fourth angle, so that the first fluid spring element and the second fluid spring element are arranged symmetrically to one another with respect to the plane formed from the vehicle seat longitudinal direction and the vehicle seat height direction. 
     However, it is also possible that the first angle has a different value from the third angle and that the second angle has a different value from the fourth angle. 
     It is pointed out that “symmetrical” is to be understood to mean in the neutral state or the neutral position, i.e. no external force is acting on the vehicle seat. With a suspension movement of the vehicle seat, the arrangement of the fluid spring elements in relation to one another changes since, in particular during a rolling movement, one fluid spring element is compressed and the other fluid spring element is correspondingly decompressed, i.e. one fluid spring element is compressed and the other fluid spring element is stretched in its length. 
     According to a particularly preferred embodiment, it is provided that the first angle and the second angle can each assume a value from a range of 0 to 90°]. 
     According to a further preferred embodiment, it is provided that the third angle and the fourth angle can each assume a value from a range of 0 to 90°]. 
     It is particularly preferably provided that the first angle, the second angle, the third angle and the fourth angle cannot assume the angle value 90°, i.e. the angles can each assume a value in the range of 0 to 90°[. This means that, when seen in particular in the vehicle seat height direction, the spring elements do not correspond to a vertical spring. 
     According to a particularly preferred embodiment, it is provided that the pumping of the fluid is such that during a deflection of the vehicle seat, depending on the direction and type of deflection, fluid is pumped from the first fluid spring element to the second fluid spring element or vice versa, and the pumping of the fluid is prevented during a neutral position of the vehicle seat. 
     According to a further preferred embodiment, it is provided that a differential pressure measuring device is provided, which is fluidically connected to the first fluid spring element and the second fluid spring element and is arranged parallel to the pump unit, the differential pressure measuring device being provided and configured to detect pressure fluctuations between the first fluid spring element and the second fluid spring element. 
     In particular, in the event of rolling movements, fluid is pumped between the fluid spring elements. If the vehicle seat is not deflected or the vehicle seat is deflected vertically, no pumping is necessary since the vehicle seat upper part remains in its horizontal arrangement. 
     A distinction is made between different deflections in terms of type. A first deflection is conceivable when the vehicle is in an inclined position or is constantly moving in an inclined position, for example when ploughing or the like. The pump unit pumps fluid from one fluid spring element to the other fluid spring element until the vertical force of the individual fluid spring elements is the same, i.e. the vehicle seat upper part is held in the horizontal position. The differential pressure measuring device can preferably be used to determine an amount of air which is to be pumped between the first fluid spring element and the second fluid spring element. Due to the general relationship between acting force, pressure and (effective) surface A, the pressure deviation or pressure difference can be recorded by means of the differential pressure measuring device and thus the force can be adjusted. 
     In this way, the required amount of fluid can be determined by means of the differential pressure measuring device. 
     A second deflection is conceivable when the vehicle is moving dynamically, i.e. the vehicle is subject to vibration which is also transmitted to the vehicle seat. A distinction must be made between high-frequency and low-frequency vibration. 
     With the low-frequency vibration, the vehicle is rocked in a low frequency range. Pressure fluctuations in the fluid spring elements are preferably determined by means of the differential pressure measuring device and the pump unit is controlled accordingly. A prerequisite for this is, of course, that the pump unit is designed to be able to provide this output, i.e. with regard to the pump output and the fluid throughput. 
     In the case of a high-frequency vibration with a small amplitude, the situation is different. The differential pressure measuring device registers changes in the differential pressure which do not exceed a definable pressure level. The amplitude ratio between the amplitude of the suspension in the roll direction and the deflection of the vehicle is less than 1, so that the vibrating system is in a (super)critical range. Pumping by means of the pump unit is uneconomical in this case and is deactivated or interrupted, since a pump that is too large or a pump with a high pumping capacity would be necessary. 
     Another situation is a high-frequency vibration with a large amplitude, which means that a sudden change in the differential pressure which exceeds the definable pressure level is registered. 
     For this case, it is provided according to a preferred embodiment that a first valve element is provided which is arranged parallel to the pump unit, the valve element being opened in the event of a high-frequency deflection with a large amplitude, and otherwise being closed. 
     The sudden opening of the first valve element can result in a sudden pressure equalization between the fluid spring elements so that, due to the inertia of the vehicle seat upper part, the original position thereof, i.e. the horizontal position of the vehicle seat upper part, can be maintained. 
     According to a further preferred embodiment, it is provided that a second valve element and a third valve element are provided, the second valve element being fluidically connected to the first fluid spring element and the third valve element being fluidically connected to the second fluid spring element, the second valve element and the third valve element being arranged parallel to one another, and the second valve element and the third valve element being fluidically connected to a compressor unit by means of a fourth valve element, a fluid being able to be fed into a fluid spring element or into both fluid spring elements or from one or both fluid spring elements depending on a switching position of the second valve element, the third valve element, and the fourth valve element. 
     The system can be filled with the fluid via the compressor unit so that the basic height of the suspension can be adjusted. The fourth valve element, which is preferably designed as a 3/2-way valve, is used for the air outlet and thus for setting a lower seat position. The second valve element and the third valve element must be activated together with the compressor unit, so that the air can continue to flow to the air springs. When actuating only one of these valves, one fluid spring element can be subjected to more pressure than the other. This serves, for example, to compensate for static deflection. 
     Furthermore, the fluid can be pumped from the one fluid spring element into the other fluid spring element by means of the pump unit. This is the implementation of the active vibration isolation described in the roll direction. The first valve element must have a significantly larger flow cross section than the second valve element and the third valve element. A rapid pressure equalization between the fluid spring elements can thus take place when the fourth valve element is actuated. This is helpful, for example, if the seat upper part of the suspension is to hold its horizontal position during very fast movements of the vehicle cab floor. Opening this line then does not generate any additional force component in the direction of deflection. 
     For a short reaction time, the hose lines should be as short as possible. Therefore, the fourth valve element should be arranged as close as possible between the fluid spring elements. 
     According to a further preferred embodiment, it is provided that a first sensor is arranged on the vehicle seat upper part and a second sensor is arranged on the vehicle seat lower part, deviations from the horizontal position of the vehicle seat upper part being able to be determined by means of the first sensor and an amplitude and a frequency of the deflection of the suspension lower part or cab floor being able to be determined by means of the second sensor. 
     The first sensor is preferably an angle sensor. 
     The underlying object is also achieved by a method for cushioning rolling movements of a vehicle seat according to any of claims  1  to  10 , comprising the method steps:
     a) detecting a deflection of the vehicle seat on the vehicle seat upper part and/or the deflection on the vehicle seat lower part and an amplitude and a frequency of the deflection on the vehicle seat lower part;   b) determining an amount of fluid to be pumped between the first fluid spring element and the second fluid spring element, and pumping this amount of fluid so that the vehicle seat upper part is held in a horizontal position.   

     According to a further preferred embodiment, it is provided that the first axis of rotation is arranged parallel to the vehicle seat longitudinal direction, and preferably the second axis of rotation and the third axis of rotation are arranged running in the vehicle seat width direction and the second and the third axis of rotation are arranged parallel to one another. 
     In particular, the arrangement of the second axis of rotation and the third axis of rotation can prevent the scissor arrangement with the spring element support from tilting, in particular when the vehicle seat upper part moves relative to the vehicle seat lower part. 
     According to a particularly preferred embodiment, it is provided that the first axis of rotation is defined by a shaft which is rotatably connected to the vehicle seat lower part. The shaft preferably has a first end and a second end, wherein the first end and the second end each are rotatably connected to the vehicle seat lower part. Instead of a shaft, a rod element is also conceivable, wherein it is possible for the shaft or the rod element to be cylindrical or angular. If the rod element is angular, it is rotatably connected to the vehicle seat lower part. 
     According to a further preferred embodiment, it is provided that the first scissor arm is connected to the vehicle seat upper part by means of a first floating bearing and to the shaft by means of a second floating bearing, and the second scissor arm is connected to the vehicle seat upper part by means of a third floating bearing and to the shaft by means of a fourth floating bearing. Such a configuration also allows a pitching suspension movement of the vehicle seat by means of the suspension unit. 
     According to the design of the first scissor arm and the second scissor arm by means of four floating bearings for connection to the vehicle seat upper part and the vehicle seat lower part, it is achieved that a stronger pitching movement of the vehicle seat is obtained when the vehicle seat is pitched and when the vehicle seat upper part follows the vehicle seat lower part accordingly. Because four floating bearings are provided, the suspension unit is mechanically indeterminate, i.e. degrees of freedom still exist which cannot be adequately determined. In order to further minimize these degrees of freedom, a first connecting element and a second connecting element are provided, which minimize the degrees of freedom of the four floating bearings through the corresponding arrangement with the first scissor arm and the second scissor arm and the vehicle seat upper part and the vehicle seat lower part. Particularly preferably, a first connecting element is provided which connects the first scissor arm to a fixed bearing which is arranged on the shaft, and wherein a second connecting element is provided which has a first connecting element part and a second connecting element part, wherein the first connecting element part is rotatably connected to the second scissor arm and the second connecting element part, and wherein the second connecting element part is rotatably connected to the first connecting element part, the first scissor arm, and the vehicle seat upper part. 
     According to a further preferred embodiment, it is provided that the second floating bearing and the fourth floating bearing are each designed as a displacement element so that the first scissor arm and the second scissor arm are in each case displaceable relative to the shaft. A displacement with respect to the shaft means that a displacement of the first scissor arm and of the second scissor arm is provided in the vehicle seat longitudinal direction. The displacement element can be designed as a sliding element or as a rolling element, so that a smooth displacement of the first scissor arm and the second scissor arm relative to the shaft can be ensured. 
     According to a further preferred embodiment, it is provided that, when viewed in the longitudinal direction of the vehicle seat, the second floating bearing is arranged in front of the third floating bearing and the first floating bearing is arranged in front of the fourth floating bearing. 
     By a rolling movement of the vehicle seat and a corresponding tracking of the spring support element, which is in connection with the first or the second fluid spring element, which can in particular be designed to be resiliently deformable, the spring support element causes deformation of the fluid spring elements, whereby a spring force or a resetting force of the fluid spring elements is generated. 
     Further advantageous embodiments result from the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional aims, advantages and expedient uses of the present invention can be found in the following description in conjunction with the drawings, in which: 
         FIG. 1A  is a perspective view of a vehicle seat according to a preferred embodiment; 
         FIG. 1B  shows the vehicle seat according to  FIG. 1A  in a further embodiment; 
         FIG. 2A  shows the vehicle seat according to a preferred embodiment in a neutral position; 
         FIG. 2B  shows the vehicle seat according to  FIG. 2A  deflected position; 
         FIG. 3A  shows the scissor arrangement according to a first embodiment; 
         FIG. 3B  shows the scissor arrangement according to a second embodiment; 
         FIG. 4A  is a schematic representation of the vehicle seat according to  FIG. 1A  in the neutral position; 
         FIG. 4B  is a schematic representation of the vehicle seat according to  FIG. 1A  in the downwardly displaced position; 
         FIG. 5A  is a first perspective view of the spring support element; 
         FIG. 5B  is a second perspective view of a spring support element. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, the same components are denoted by the same reference signs, wherein it is possible for the reference signs to be omitted in some drawings for greater clarity. 
       FIG. 1A  shows a vehicle seat  1  or a vehicle seat substructure  1 ′, wherein the vehicle seat  1  has a vehicle seat upper part  3  and a vehicle seat lower part  4 , which are connected to one another by means of a suspension unit  2  in such a way that the vehicle seat upper part and the vehicle seat lower part can be moved and cushioned relative to one another. It can also be seen that the suspension unit  2  is rotatably connected about a first axis of rotation  10  to the vehicle seat lower part  4 . 
     The suspension unit  2  comprises a scissor arrangement  5  having a first scissor arm  6  and a second scissor arm  7 , wherein the suspension unit further comprises a spring element support  11  and a first fluid spring element  12  and a second fluid spring element  13 . As can be seen, the spring element support is rotatably connected about a second axis of rotation to the first scissor arm and rotatably connected about a third axis of rotation  15  to the second scissor arm  7 , wherein the first fluid spring element  12  is connected to the vehicle seat lower part  4  on the one hand and to the spring element support  11  on the other hand, wherein the first fluid spring element  12  is further arranged at a first angle  16  to a vehicle seat width direction B and at a second angle  17  to a vehicle seat height direction H. 
     The more detailed arrangement of the fluid spring elements  12 ,  13  and the more detailed configuration of the scissor arrangement  5  are described further in the following drawings. 
     The first fluid spring element  12  and the second fluid spring element  13  are embodied in  FIG. 1A  as a resiliently deformable air spring. 
     It is also conceivable that the first spring element  12  is designed as an air spring and the second spring element  13  as a mechanical spring, or vice versa. 
     Furthermore, the scissor arrangement  5  has a first connecting element  25  and a second connecting element  26 , wherein the second connecting element  25  has a first connecting element part  27  and a second connecting element part  28 , wherein the first connecting element  25  is rotatably connected to the first scissor arm  6  and on the other hand is connected to a first fixed bearing  29 , wherein the first fixed bearing  29  is connected to a shaft  20 . 
     Furthermore, the first connecting element part  27  is rotatably connected to the second scissor arm  7  and rotatably connected to the second connecting element part  28 , wherein the second connecting element part  28  is further rotatably connected to the first scissor arm  7  and connected to the vehicle seat upper part  3  by means of a fixed bearing  30 . 
       FIG. 1B  shows the same vehicle seat  1  as shown in  FIG. 1A , wherein damper elements  33  are additionally provided, wherein at least one damper element  33 , preferably at least two damper elements  33  and particularly preferably four damper elements  33  are provided, which are each arranged at an angle to the vehicle seat longitudinal direction L, the vehicle seat width direction B and the vehicle seat height direction H. Furthermore, the damper elements  33  are connected on the one hand to the spring element support  11  and on the other hand to the vehicle seat lower part  4 . 
     In  FIGS. 2A and 2B , a vehicle seat  1  according to an embodiment of the invention is shown schematically, wherein the vehicle seat  1  according to  FIG. 2A  is shown in the neutral position N or horizontal position and according to  FIG. 2B  is shown in a rolling position W, wherein the rolling position W has already been compensated for, since the vehicle seat upper part  3  is in the horizontal position. 
     The underlying components as well as the arrangement and function thereof are briefly described and illustrated below. 
     In particular, a pump unit  57  is provided which is in fluidic connection with the first fluid spring element  12  and the second fluid spring element  13 . In the event of a rolling movement of the vehicle seat  1 , which is caused by an external force acting on the vehicle seat  1 , a pressure equalization is carried out between the first fluid spring element  12  and the second fluid spring element  13  depending on the type of deflection or rolling movement. 
     It is provided that the pumping of the fluid is such that during a deflection of the vehicle seat  1 , depending on the direction and type of deflection, fluid is pumped from the first fluid spring element  12  to the second fluid spring element  13  or vice versa, and the pumping of the fluid is prevented during a neutral position of the vehicle seat  1 . 
     The neutral position or horizontal position means that no force acts on the vehicle seat and in particular the vehicle seat upper part  3 , so that the vehicle seat upper part  3  remains in the horizontal position. 
     It is further provided that a differential pressure measuring device  56  is provided which is fluidically connected to the first fluid spring element  12  and the second fluid spring element  13  and is arranged parallel to the pump unit  57 , the differential pressure measuring device  56  being provided and configured to detect pressure fluctuations between the first fluid spring element  12  and the second fluid spring element  13 . 
     In particular, in the event of rolling movements, fluid is pumped between the fluid spring elements  12 ,  13 . If the vehicle seat  1  is not deflected or the vehicle seat  1  is deflected vertically, no pumping is necessary since the vehicle seat upper part  3  remains in its horizontal arrangement. 
     A distinction is made between different deflections in terms of type. A first deflection is conceivable when the vehicle is in an inclined position or is constantly moving in an inclined position, for example when ploughing or the like. The pump unit  57  pumps fluid from the one fluid spring element  12 ,  13  to the other fluid spring element  12 ,  13  until the acting vertical force of the individual fluid spring elements  12 ,  13  is the same, i.e. the vehicle seat upper part  3  is held in the horizontal position. The differential pressure measuring device  56  can be used to determine an amount of air which is to be pumped between the first fluid spring element  12  and the second fluid spring element  13 . Due to the general relationship between acting force, pressure and (effective) surface A, the pressure deviation or pressure difference can be recorded by means of the differential pressure measuring device and thus the force can be adjusted. 
     In this way, the required amount of fluid can be determined by means of the differential pressure measuring device  56 . 
     A second deflection is conceivable when the vehicle is moving dynamically, i.e. the vehicle is subject to vibration which is also transmitted to the vehicle seat  1 . A distinction must be made between high-frequency and low-frequency vibration. 
     With the low-frequency vibration, the vehicle is rocked in a low frequency range. Pressure fluctuations in the fluid spring elements are preferably determined by means of the differential pressure measuring device  56  and the pump unit  57  is controlled accordingly. A prerequisite for this is, of course, that the pump unit  57  is designed to be able to provide this output, i.e. with regard to the pump output and the fluid throughput. 
     In the case of a high-frequency vibration with a small amplitude, the situation is different. The differential pressure measuring device  56  registers changes in the differential pressure, i.e. the pressure difference between the pressures of the first fluid spring element  12  and the second fluid spring element  13 , which do not exceed a definable pressure level. The amplitude ratio between the amplitude of the differential pressure and the deflection of the vehicle is less than  1 , so that the vibrating system is in a (super)critical range. Pumping by means of the pump unit  57  is uneconomical in this case and is deactivated or interrupted, since a pump that is too large or a pump with a high pumping capacity would be necessary. 
     Another situation is a high-frequency vibration with a large amplitude, which means that a sudden change in the differential pressure which exceeds the definable pressure level is registered. 
     For this case, it is provided according to a preferred embodiment that a first valve element  51  is provided which is arranged parallel to the pump unit  57 , the first valve element  51  being opened in the event of a high-frequency deflection with a large amplitude and otherwise being closed. 
     The sudden opening of the first valve element  51  can result in a sudden pressure equalization between the fluid spring elements  12 ,  13  so that, due to the inertia of the vehicle seat upper part  3 , the original position thereof, i.e. the horizontal position of the vehicle seat upper part  3 , can be maintained. 
     According to a further preferred embodiment, it is provided that a second valve element  52  and a third valve element  53  are provided, the second valve element  52  being fluidically connected to the first fluid spring element  12  and the third valve element  53  being fluidically connected to the second fluid spring element  13 , the second valve element  52  and the third valve element  53  being arranged parallel to one another, and the second valve element  52  and the third valve element  53  being fluidically connected to a compressor unit  55  by means of a fourth valve element  54 , a fluid being able to be fed into a fluid spring element  12 ,  13  or into both fluid spring elements  12 ,  13  or from one or both fluid spring elements  12 ,  13  depending on a switching position of the second valve element  52 , the third valve element  53  and the fourth valve element  54 . 
     In order to be able to convey fluid into the system, it is necessary that the fourth valve element  54  is open. If the fourth valve element  54  is closed, no fluid can be conveyed to the fluid spring elements  12 ,  13 . 
     If the fourth valve element  54  is open, the following positions of the second valve element  52  and the third valve element  53  can be possible:
         the second valve element  52  and the third valve element  53  are open;   the second valve element  52  is open and the third valve element  53  is closed;   the second valve element  52  is closed and the third valve element  53  is open.       

     If both valve elements  52 ,  53  are open, fluid can flow into both fluid spring elements  12 ,  13 , whereby the seat position can be adjusted. 
     If only one of the two valve elements  52 ,  53  is open, only the correspondingly associated fluid spring element  12 ,  13  is filled with fluid or fluid is removed. This is particularly advantageous when driving on a slope or the like. 
     The system can be filled with the fluid via the compressor unit  55 , which is fluidically connected to a fluid source  58 , so that the basic height of the suspension can be adjusted. The fourth valve element  54 , which is preferably designed as a 3/2-way valve, is used for the fluid outlet and thus for setting a lower or higher seat position. The second valve element  52  and the third valve element  53  must be activated together with the compressor unit  58 , so that the air can continue to flow to the fluid spring elements  12 ,  13 . When actuating only one of these valve elements  52 ,  53 , one fluid spring element  12 ,  13  can be subjected to more pressure than the other. This serves, for example, to compensate for static deflection. 
     Furthermore, the fluid can be pumped from the one fluid spring element  12 ,  13  into the other fluid spring element  12 ,  13  by means of the pump unit  57 . This is the implementation of the active vibration isolation described in the roll direction W. The first valve element  51  has a significantly larger flow cross section than the second valve element  52  and the third valve element  53 . A rapid pressure equalization between the fluid spring elements  12 ,  13  can thus take place when the fourth valve element  54  is actuated. This is helpful, for example, if the vehicle seat upper part  3  of the suspension is to hold its horizontal position during very fast movements of the vehicle cab floor. Opening this line then does not generate any additional force component in the direction of deflection. 
     For a short reaction time, the hose lines, which represent the fluidic connections between the respective elements, should be as short as possible. Therefore, the fourth valve element  54  should be arranged as close as possible between the fluid spring elements  12 ,  13 . 
     According to a further preferred embodiment, it is provided that a first sensor  49  is arranged on the vehicle seat upper part  3  and a second sensor  50  is arranged on the vehicle seat lower part  4 , deviations from the horizontal position of the vehicle seat upper part  3  being able to be determined by means of the first sensor  49  and an amplitude and a frequency of the deflection of the vehicle seat  1  being able to be determined by means of the second sensor  50 . 
     A first embodiment of the scissor arrangement  5  can be seen in  FIG. 3A  and a second embodiment of the scissor arrangement  5  can be seen in  FIG. 3B . 
     The embodiment of the scissor arrangement  5  according to  FIG. 3A  will be described first. 
     The scissor arrangement  5  comprises a first scissor arm  6 , a second scissor arm  7 , a third scissor arm  8  and a fourth scissor arm  9 . 
     The designs of the third scissor arm  8  and the fourth scissor arm  9  apply correspondingly to the associated first scissor arm  5  and the associated second scissor arm  7 . This is particularly true since the third scissor arm  8  runs identically to the first scissor arm  6  and the fourth scissor arm  9  runs identically to the second scissor arm  7 . 
     As can also be seen, the spring element support  11  is provided, which is rotatably connected about a second axis of rotation  14  to the first scissor arm  6  and rotatably connected about a third axis of rotation  15  to the second scissor arm  7 . 
     Furthermore, the first scissor arm  6  is connected to the vehicle seat upper part  3  by means of a first floating bearing  21  and to a shaft  20  by means of a second floating bearing  22 , and the second scissor arm  7  is connected to the vehicle seat upper part  3  by means of a third floating bearing  23  and to the shaft  20  by means of a fourth floating bearing  24 , wherein a first connecting element  25  connects the first scissor arm  6  to a first fixed bearing  29  which is arranged on the shaft  20 , and wherein a second connecting element  26  is provided which has a first connecting element part  27  and a second connecting element part  28 , wherein the first connecting element part  27  is rotatably connected to the second scissor arm  7  and the second connecting element part  28 , and wherein the second connecting element part  28  is rotatably connected to the first connecting element part  27 , the first scissor arm  6  and the vehicle seat upper part  3 . The second connecting element part  28  is rotatably connected in particular to a second fixed bearing  30 . The second fixed bearing is arranged on the vehicle seat upper part  3 . 
     The first floating bearing  21  and the second floating bearing  23  are each designed as running rollers  36 , which are rotatably connected to the respective scissor arm  6 ,  7 ,  8 ,  9  and are mounted in a rolling manner in a running rail  37 , wherein the running rail  37  is arranged on the vehicle seat upper part  3 . 
     The second floating bearing  22  and the fourth floating bearing  24  are designed in such a way that a first displacement element  31  and a second displacement element  32  are provided, wherein the first scissor arm  6  is rotatably connected to the first displacement element and the second scissor arm  7  is rotatably arranged on the second displacement element  32 . 
     The displacement elements  31 ,  32  can be displaced in such a way that they can be displaced with respect to the shaft  20  in the direction of the first axis of rotation  10 . 
     The first displacement element  31  and the second displacement element  32  are displaced in particular when the vehicle seat  1  carries out a vertical movement. 
     Because the scissor arms  6 ,  7 ,  8 ,  9  are each connected to the vehicle seat lower part or to the vehicle seat upper part  3  by means of a floating bearing, it is necessary to limit the degrees of freedom with regard to the movement of the scissor arrangement  5 . This is done by means of the first connecting element  25  and the second connecting element  26 . 
     Furthermore, the spring element support  11  has an adapter plate  38 , by means of which the respective fluid spring element  12 ,  13  (not shown here) can be connected to the spring element support  11 . 
     The second embodiment, which is shown in  FIG. 3B , is identical in terms of its functional principle to the embodiment of  FIG. 3A , although the configuration differs. 
     The embodiment of  FIG. 3B  also comprises a first scissor arm  6 , a second scissor arm  7 , a third scissor arm  8 , and a fourth scissor arm  9 , wherein the first scissor arm  6  and the third scissor arm  8  as well as the second scissor arm  7  and the fourth scissor arm  9  each run identically. Likewise, the respective scissor arms  6 ,  7 ,  8 ,  9  are guided in the guide rail  37  of the vehicle seat upper part  3  by means of a floating bearing  21 ,  23  which is designed as a running roller  36 . 
     This embodiment also has the first connecting element  25  and the second connecting element  26  in the same arrangement and function as described in  FIG. 3A . 
     The arrangement of the floating bearings  22 ,  24  with respect to the vehicle seat lower part  4  is different in this case. In particular, a support part  40  is shown which is rotatably connected to the vehicle seat lower part  4  about the first axis of rotation  10 . A shaft  20  is provided at the front and the rear end of the support part in the vehicle seat longitudinal direction L, the support part  40  also having running rails  37  in which the floating bearings  22 ,  24  can roll by means of running rollers  36  with respect to the support part  40 . 
     The first fixed bearing  29 , by means of which the first scissor arm  6  is connected by means of the first connecting element  25 , is also arranged on the support part  40 . 
     A lower adapter plate  39  is also shown schematically in  FIG. 3B , by means of which the fluid spring element  12 ,  13  can in each case be connected to the vehicle seat lower part  4 . As can be seen, the lower adapter plate  39  has an inclined portion, by means of which the angle of the corresponding fluid spring element  12 ,  13  can be adjusted. 
     The same also applies to the upper adapter plate  38 , which has an angle with respect to the vehicle seat width direction B, wherein the inclination of the upper adapter plate  38  and of the lower adapter plate  39  are parallel to one another. 
     In  FIGS. 4A and 4B , the kinematics of the moving parts of the vehicle seat  1  is shown again schematically. 
     In  FIG. 4A , the vehicle seat is shown in the neutral position N and in  FIG. 4B  in the downward position U. 
     The movement of the moving parts, which are denoted by the corresponding reference signs, can be seen by comparing  FIGS. 4A and 4B . 
     Furthermore,  FIGS. 5A and 5B  show the spring element support  11  in a first perspective representation and in a second perspective representation. 
     The spring element support  11  has a first spring element support holder  45  and a second spring element support holder  46 , which are connected to one another by means of a connecting part  47 . The respective spring element support holder  45 ,  46  has a first connection point  42  and a second connection point  43 , by means of which the spring element support can be connected, in particular rotatably, to the first scissor arm  6  and the second scissor arm  7 , or to the third scissor arm  8  and the fourth scissor arm  9 . 
     Furthermore, both the first spring element holder  45  and the second spring element holder  46  have an adapter plate holder  44 , by means of which the upper adapter plate  38  can be connected to the spring element support. 
     All features disclosed in the application documents are claimed as being substantial to the invention, provided that they are, individually or in combination, novel over the prior art. 
     LIST OF REFERENCE SIGNS 
       1  Vehicle seat 
       2  Suspension unit 
       3  Vehicle seat upper part 
       4  Vehicle seat lower part 
       5  Scissor arrangement 
       6  First scissor arm 
       7  Second scissor arm 
       8  Third scissor arm 
       9  Fourth scissor arm 
       10  First axis of rotation 
       11  Spring element support 
       12  First fluid spring element 
       13  Second fluid spring element 
       14  Second axis of rotation 
       15  Third axis of rotation 
       20  Shaft 
       21  First floating bearing 
       22  Second floating bearing 
       23  Third floating bearing 
       24  Fourth floating bearing 
       25  First connecting element 
       26  Second connecting element 
       27  First connecting element part 
       28  Second connecting element part 
       29  First fixed bearing 
       30  Second fixed bearing 
       31  First displacement element 
       32  Second displacement element 
       33  Damper element 
       34  First end of the shaft 
       35  Second end of the shaft 
       36  Running roller 
       37  Running rail 
       38  Adapter plate 
       39  Lower adapter plate 
       40  Support part 
       41  Locking element 
       42  First connection point 
       43  Second connection point 
       44  Adapter plate holder 
       45  First spring element support holder 
       46  Second spring element support holder 
       47  Connecting part 
       48  Damper element holder 
       49  First sensor 
       50  Second sensor 
       51  First valve element 
       52  Second valve element 
       53  Third valve element 
       54  Fourth valve element 
       55  Compressor unit 
       56  Differential pressure measuring device 
       57  Pump unit 
       58  Fluid source 
       59  Control unit 
     N Neutral position 
     O Upward deflected position 
     U Downward deflected position 
     W Rolling position 
     L Vehicle seat longitudinal direction 
     B Vehicle seat width direction 
     H Vehicle seat height direction