DE4221088A1 - Suspension system for motor vehicle with actuator(s) between bodywork and wheel axle bearer - has valve arrangement and servo valve increasing springed rigidity if effectiveness of pressure control arrangement is insufficient - Google Patents

Abstract

The actuator provides at least one working chamber contg. a compressed medium for variable working pressure. This working chamber is connected to a storage system influencing the stiffness of the sprung suspension system as well as to a pressure control arrangement for introducing and removing compressed medium into and out of the working chamber. A control valve (20) assigned to the actuator (2) is pref. a proportional valve operated via an electromagnet (62). The actuator has an actuating piston (6) slidable within a cylinder (4). The servo valve (70) operates electromagnetically by an electromagnet (76) and a return spring (78). The control system operates electronically with electrical leads to the actuatable components of the suspension system as well as to sensors and operating elements. If, for instance, the electronic control determines, with the aid of an entered program, that the suspension system is not working properly and/or a relevant actuatable component is not functioning properly and/or the pressure source (10) is switched off or is out of service the suspension system is brought to its basic state. ADVANTAGE - Can still be driven in basic state without electrical current. Sprung rigidity and damping required can be reduced. Rapid niveau regulation.

Description

State of the art

The invention is based on a suspension system for vehicles according to the preamble of claim 1 and by a method for operating ben this suspension system according to the preamble of claim 37.

Suspension systems for vehicles with quasistati have been around for a long time Control option for conventional level control. The An Requirements for such suspension systems are very low. This Suspension systems are based on a present invention horizontal suspension system hardly comparable.

Recently, there have also been vehicles with a suspension system with a so-called rapid level control (SNR). With egg Such a suspension system can with the help of at least one the forces actuated by a pressure control device actively influenced between a vehicle body and a wheel carrier become.

If the level control is not ready for operation, i. H. if the Pressure control device can no longer work properly NEN considerable in vehicles with such a level control Disadvantages occur, which will be discussed below.  

The level control is only ready for operation if certain prerequisites tongues are present. It is not operational if e.g. Legs Control electronics level due to a detected error regulation is put out of operation or if e.g. B. not a solenoid valve works etc. To operate the suspension system you need one Drive. This can be the vehicle drive motor, for example. The level control is therefore not ready even if the drive is switched off when the vehicle is stationary.

If the level control is not operational, i. H. if the Pressure control device is not working properly, then the Actuator no pressure medium can be supplied, or none can Print medium can be drained.

In vehicles with a suspension on which the invention is based system is between the vehicle body and the wheel carrier Actuator installed. With the help of the actuator and a pressure control the forces or the level of the vehicle body can be set. The force acting on the actuator can increase fluctuate Lich, z. B. by changing the payload when cornering and when accelerating or braking.

For suspension systems with a fast level control (SNR) will be influences from load changes as well as driving maneuvers and relatively boring bumps are caused by the Aktua adjusted by supplying pressure medium to the actuator or Drains pressure medium from the actuator.

Depending on the design, the actuator comprises at least one with pressure medium loadable work area. To achieve a spring This work area is connected to a hydraulic accumulator. In order to the actuator also works in conjunction with the hydraulic accumulator Feather. Between the work area and the hydraulic accumulator and / or between  Between the work room and a second work room, a damper tion throttle be interposed. The actuator also receives still the function of a shock absorber.

The low-frequency and medium-frequency influences can be active by supplying pressure medium or draining pressure medium be regulated. To ensure good insulation in the high-frequency range The suspension system must reach unevenness in the road very soft, d. H. be provided with low spring stiffness, and the damping throttle can be designed with a low damping effect his. In such a suspension system, the spring stiffness speed much smaller than with a conventional, passive opening hanging system. This leads to a very comfortable suspension system.

If with this suspension system with the very small spring stiffness If the level control is not ready for operation, this leads that z. B. with a load change the vehicle body very far down or up from its desired central position deflects. Increases z. B. before the vehicle drive motor started will, d. that is, before the level control is operational, someone on, the vehicle body is pushed very far down. This has significant drawbacks to boarding comfort and it can e.g. B. sit an open vehicle door on a curb, or the mechanical end stops of the undercarriage come into contact. On the other hand, in this suspension system after the ignition key has been removed, the driver or a passenger gets out, then the vehicle body moves up until the mechani end stops rudely stop the movement of the vehicle body.

The known suspension system comprises a hydraulic pump, control valves tile, pressure transducer and control electronics. If the tax electronics finds that z. B one of the electrical components  does not work properly, the control electronics interrupts the Level control. That is, the pressure control device for supplying the Actuator with pressure medium is switched off. In this case, the Actuator no longer work in the desired manner. Because of the The small spring stiffness of this system is safe driving no longer possible with this vehicle because the vehicle body or the wheel carrier would no longer be able to control vertical movements To run. It is particularly dangerous if the rapid level control suddenly fails and is no longer operational ready.

Advantages of the invention

In contrast, the suspension system designed according to the invention with the characterizing features of claim 1, that in the event of a failure z. B. an electrical component of the on suspension system the vehicle without any problems, similar to a convention bright, steel-sprung vehicle that can continue to drive. Even in the case a suddenly occurring defect becomes a dangerous driving situation prevented. The vehicle maintains good driving stability. At Failure z. B. the vehicle drive motor or when switched off Vehicle drive motors are advantageous when the load changes only small changes in the level of the vehicle body. The suspension system z. B. can be designed so that this Än changes are not greater than with a tightly laid out, with conventional steel spring suspension system.

The proposed suspension system offers another advantage Possibility that the spring for normal, regulated driving stiffness and, depending on the embodiment of the invention, also Damping can be designed smaller than in previously known Suspension systems. This gives you the normal, regulated Driving operation a much better driving comfort.  

By increasing the spring stiffness and possibly also the damping if the pressure control device fails, there is no need any regarding the two possible driving modes To compromise.

By the method according to the invention with the characteristic note paint the claim 37, the suspension system in desired Ar with technically feasible components in a vehicle work.

The measures listed in the subclaims provide for partial training and improvements to the suspension system and the method for operating the suspension system possible.

A particularly simple suspension system results if one Valve device is used with which the effective size of the Storage system can be changed. Given the size of the spit chersystems designed changeable, so that automatically results in one particularly simple, advantageous possibility of changing the spring stiffness.

You can train the valve device so that when it is not the position in which the Spring stiffness is increased. This has the advantage that e.g. B. in the event of an electrical failure of the control of the valves direction automatically results in the desired greater spring stiffness.

The storage system can be divided into several storage elements and design the valve device so that in its function lung, in which the greater spring stiffness should result, the Pressure medium not from the working space of the actuator in at least one the storage elements can get. This has the advantage that automatically and easily the spring stiffness enlarged.  

In a special embodiment of the invention, the Ven tileinrichtung in the course of the connection between the work space and arrange the pressure control device and train so that at in said functional position of a valve device Flow of pressure medium from the work space towards the pressure control device is not possible. Among other things, this offers the Advantage that regardless of the tightness of the pressure control device even when the vehicle drive motor is stationary for a long time tool structure remains at the desired height without slowly sinking.

If you put the first storage element between the valve device and arranges the pressure control device, so you get a special simple structure and small number of necessary pressure medium lei tion, advantageously without restriction in function.

The suspension system can advantageously be designed such that with valve device in said functional position a throttling of the pressure medium is switched on during the Ak tuator works in the retracting stroke. One can also get an appropriate one Provide throttling for the actuator's extension stroke. This offers the advantage that not only the spring stiffness is increased, but also the damping of the actuator in an advantageous manner elevated.

A particularly simple, component-saving, advantageous construction arises when one sees the connection between the work space and leads the second storage element via the valve device and the Forms valve device so that in said functional position the additional throttling in the course of the connection between the Work space and the second storage element is effective.

Particularly small control energy is required when using a Pilot valve for actuating the valve device. Reduce this gert considerably the electrical effort in an advantageous manner.  

Another advantageous reduction in the amount of electrical work Components and consumption of electrical power or electrical Energy arises when you pass multiple valve devices through one common pilot valve operated. This is particularly advantageous special that very few electromagnets are required.

By providing an in case of insufficient work of the Pressure control device, the pressure control device relieves pressure Relief valve is advantageously obtained with particularly good radio tion security.

The pressure control device can be used, for example, with the aid of a Form pressure source, a pressure sink and a control valve and design the control valve so that in its unactuated position a flow of pressure medium from the valve device in Rich tion of the pressure sink is possible. This is more advantageous also relieves the first storage element.

You can implement the valve device with a valve seat, egg valve body and an actuator for actuating the valve body. Is the valve body when the actuator is not actuated due to the pressure in the working space of the actuator Closing direction applied, so it is ensured in any case, that in the event of a defect or when the level control is switched off the pressure medium cannot escape unintentionally from the actuator.

Is the valve body by an elastic element in the closing direction tion applied, then advantageously always results precisely defined position of the valve body.

The valve device can be designed such that in the position in which the spring stiffness is increased, the damping also increases is what enables a particularly safe driving of the vehicle.  

A damping throttle valve can be used in the valve device tion of the printing medium, which is advantageously the Formation of any desired damper characteristic curve possible light. The damper characteristic can advantageously be such that this z. B. an optimal, conventional, not actively taxable corresponds to the chassis.

The throttling of the pressure medium can be used for the two flow directions different sizes. This has the advantage that for the Entry stroke and different characteristic curves for the extension stroke reali are sizable.

The valve device can be designed so that when applied of the actuator with control pressure part of the pressure medium in Rich direction of the first memory element and flow the memory element can fill. This advantageously enables a particularly gentle Starting behavior of the suspension system.

In the control passage in the direction of the first storage element can one in a special embodiment of the invention, the pressure Arrange medium throttling preload valve. This gives an advantage Safely working the valve device. The valve body is always in a precisely definable position.

A particularly small design is obtained when the control is carried out let it through the spool.

Receives a particularly advantageous embodiment of the invention one when the control passage is actuated in the opening direction Valve body closes, so that advantageously the control pressure in can be at full height on the actuator of the valve device.  

A particularly advantageous, long-lasting and very tight-fitting Valve device is obtained if the valve device is made in this way forms that between the connection of the work space and the connection of the first storage element or the pressure control device two in Series connected sealing points are present, with the opening first the sealing that seals with elastic deformation and then the gap seal. During the closing process closes the gap seal first and then the one by ela static deformation sealing point. This has the advantage that the elastically sealing sealing point is protected; in particular is advantageous that in the area of this elastically sealing seal place no flow forces can be effective.

The advantageous possibility of using an elastic seal elementes guarantees even when the vehicle is stationary for a long time drive motor that ver the vehicle body at the desired height remains.

If you look at the two storage elements, each comprising a storage space prestressed with different pre-tensioning bridges, so results a particularly advantageous suspension characteristic can be easily adapted to the respective needs.

You can also design the storage system so that at least one the two storage elements comprise two or more storage spaces, which advantageously the choice of an optimal suspension characteristics stik favors.

drawing

Selected, particularly advantageous embodiments of the suspension system are shown in simplified form in the drawing and explained in more detail in the following description. There, Figs. 1 to 15 per an embodiment.

Description of the embodiments

The suspension system according to the invention can be used in any vehicle in which an actuator is installed between a vehicle body and a wheel carrier. The wheel carrier is usually a left side or a right side of a vehicle axle. A wheel is rotatably supported on the wheel carrier or on each side of the vehicle axle. Usually, actuators such as wheels are used for each vehicle in at least the same number. There are four actuators or four groups of actuators in a four-wheel vehicle. In Fig. 1, a first actuator 2 , a second actuator 2 ', a third actuator 2 ''and a fourth actuator 2 ''' are shown. The first actuator 2 is installed, for example, on the left front side of the vehicle between the vehicle body, not shown, and the left side of the front vehicle axle, also not shown, and the second actuator 2 'is located on the front right between the vehicle body and the front axle of the vehicle. Accordingly, the actuators 2 '', 2 '''are attached to the rear vehicle axle.

The actuator 2 has a cylinder 4 . An actuator piston 6 is slidably mounted within the cylinder 4 . The actuator piston 6 is attached to a piston rod 8 . The piston rod 8 projects on an end face of the cylinder 4 from the cylinder 4 out. With the other end face, the cylinder 4 is connected to the vehicle construction (not shown) or to the wheel carrier (not shown). Accordingly, the protruding from the cylinder 4 end of the Kol rod 8 is connected to the wheel carrier or to the vehicle body.

The actuators 2 ', 2 '', 2 ''' are constructed the same as the actuator 2 . For the sake of clarity, not all reference numerals are given for the actuators 2 ', 2 '', 2 '''.

Furthermore, the Fig. 1 shows a pressure source 10, a pressure sink 12, a two individual accumulators central memory 14, four check valves 16, 16 ', 16' ', 16' '', a unit 18, and four control valves 20, 20 ', 20 ′ ′, 20 ′ ′ ′. The control valve 20 is assigned to the actuator 2 . Correspondingly, the control valve 20 'for actuating the actuator 2 ' is provided, etc. In the illustrated embodiment, the control valve 20 is a pilot-operated, electromagnetically actuated proportional directional control valve with essentially three actuating positions 21 , 22 , 23 shown symbolically in the drawing. The control valves 20 ', 20 '', 20 ''' are constructed the same as the control valve 20th Because of the clarity, not all reference numerals are given in the other control valves 20 ', 20 '', 20 '''.

The pressure sink 12 consists in the illustrated embodiment of a hydraulic tank. The pressure source 10 essentially comprises a pressure and / or flow-controlled hydraulic pump and a pressure limiting valve. The hydraulic pump of the pressure source 10 is driven by a vehicle drive motor, not shown, and sucks the pressure medium from the hydraulic tank of the pressure sink 12 and conveys it into a pressure line 26 . The pressure source 10 is dimensioned so that a largely constant system pressure is present in the normal operating state of the suspension system in the pressure line 26 or in the central memory 14 . The pressure line 26 leads to the control valve 20 via the check valve 16 . A return line 28 leads from the control valve 20 via the unit 18 to the pressure sink 12 . In the same manner, the control valves 20 ', 20 '', 20 ''' are connected to the pressure line 26 and to the return line 28 . The unit 18 be found in the course of the return line 28 and is used for cooling and filtering the pressure medium before it flows back into the tank of the pressure sink 12 . Parallel to the cooler and filter of the unit 18, the unit 18 also includes a biased check valve, which among other things serves to continue operating the system even with z. B. clogged filter or cooler. The pressure medium is a fluid, preferably a hydraulic fluid.

The pressure source 10 and the control valve 20 together serve as a pressure control device 30 for actuating the actuator 2 . Accordingly, the actuator 2 'is actuated via the pressure source 10 and the control valve 20 ', which is why the pressure source 10 together with the control valve 20 'can be referred to as a pressure control device 30 ' for the actuator 2 '. Correspondingly, the control valve 20 '' and the control valve 20 '''together with the pressure source 10 form the corresponding pressure control devices 30 ''and 30 ''' for the actuator gate 2 '' and 2 '''.

Within the cylinder 4 of the actuator 2 there is a working space 32 and a second working space 34 which are filled with pressure medium. The pressure medium exchanged between the working space 32 and the second working space 34 must pass through a throttle 36 .

In the course of a connection 38 between the control valve 20 of the pressure control device 30 and the working space 32 of the actuator 2, there is a valve device 40 . Also each one of the Ventilein device 40 corresponding valve device 40 ', 40 '', 40 ''' is between the actuators 2 ', 2 '', 2 ''' and the control valves 20 ', 20 '', 20 ''' arranged. In the valve device 40 there is an actuation position 42 shown symbolically in the drawing and a function position 44 likewise symbolically shown. The connec tion 38 between the control valve 20 and the actuator 2 is composed of a line 46 and a line 48th The line 46 connects the control valve 20 to the valve device 40 , and the line 48 connects the valve device 40 to the working space 32 of the actuator 2 . In the suspension system shown in FIG. 1, there is a first storage element 50 and a second storage element 52 . The first storage element 50 and the second storage element 52 are assigned to the actuator 2 . In the same way there are the actuators 2 ', 2 '', 2 ''' associated memory elements 50 ', 50 '', 50 ''' and 52 ', 52 '', 52 '''. The storage elements 50 , 52 belong to a storage system 55 . Accordingly, the storage systems include 55 ', 55 '', 55 ''' the memory elements 50 ', 50 '', 50 ''' and 52 ', 52 '', 52 '''. The storage system 55 , 55 ', 55 '', 55 ''' affects the Fe dersteifigkeit the suspension system in the area of the corresponding actuator 2 , 2 ', 2 '', 2 '''. In the illustrated exemplary implementation in Fig. 1 comprises from the first memory element 50 a storage space 50 a, and the second memory element 52 comprises a first memory space 52 a and a second memory space 52 b. The memory space 50 a of the first memory element 50 is connected to the line 46 of the connection 38 . The storage spaces 52 a, 52 b of the second storage element 52 are connected via a line 58 with the Ventilein device 40 . There is a throttle point 60 in the area of the valve device 40 .

If the valve device 40 is in the symbolically illustrated actuation position 42 , all lines 46 , 48 , 58 are connected to one another. That is, in the actuating position 42, the control valve 20 of the pressure control device 30 , the working space 32 of the actuator 2 , the storage space 50 a of the first storage element 50 and the storage spaces 52 a, 52 b of the second storage element 52 are connected to one another. The valve device 40 is so formed that when the valve device 40 is in the functional position 44 shown symbolically in the drawing, no pressure medium from the direction of the actuator 2 and from the direction of the second storage element 52 in the direction of the first Speicherelemen tes 50 or can flow out in the direction of the control valve 20 .

If the valve device 40 is in the symbolic position 44 , then the throttle point 60 ensures throttling of the pressure medium exchanging between the working space 32 of the actuator 2 and the storage spaces 52 a, 52 b of the second storage element 52 . If the valve device 40 is switched to the actuation position 42 , then the pressure medium can largely flow unthrottled through the valve device 40 .

The pressure line 26 , the return line 28 and the line 46 of the connection 38 are connected to the control valve 20 . The control valve 20 is designed so that when it is in the first, sym bolhaft shown actuation position 21 , pressure medium from the direction of the line 46 in the direction of the return line 28 can flow. In the first actuation position 21 , the pressure line 26 in the area of the control valve 20 is closed. If the control valve 20 is in the symbolically illustrated, second actuation position 22 , the pressure line 26 , the return line 28 and the line 46 are not connected to one another. In the symbolically represented, third actuating position 23 , pressure medium can flow from the direction of the pressure line 26 in the direction of line 46 of the connection 38 ; however, in this third actuation position 23, the return line 28 in the area of the control valve 20 is closed. The control valve 20 is preferably a proportional valve which can be actuated via an electromagnet 62 . If the electromagnet 62 is not energized, a spring 64 ensures that the control valve 20 is in the symbolically illustrated first actuation position 21 . The first actuation position 21 can thus be referred to as the basic position of the control valve 20 . Depending on the strength of the flow of the electromagnet 62 , the control valve 20 passes more or less far beyond the second actuation position 22 into the third actuation position 23 . As is known to the person skilled in the art, there is usually an arbitrary number of intermediate positions in a proportional valve between the individual actuation positions.

Fig. 1 shows also a relief valve 66. The Entla stungsventil 66 has a symbolically shown actuation position 67 and a function position 68 also shown symbolically. The relief valve 66 can be actuated electromagnetically. If the electromagnet of the relief valve is de-energized, the relief valve 66 is in the functional position 68 and if the electromagnet is sufficiently energized, the relief valve 66 switches into the symbolically illustrated actuation position 67 . There is a branch from the pressure line 26 to the relief valve 66 . If the relief valve 66 is in the functional position 68 , the pressure medium can flow out of the pressure line 26 largely without pressure to the hydraulic tank of the pressure sink 12 . If the relief valve 66 is switched into the actuation position 67 , the connection via the relief valve 66 to the pressure sink 12 is blocked.

There is also a pilot valve 70 . In the pilot valve 70 one recognizes an actuation position 72 shown symbolically in the drawing and a function position 74 also symbolically shown. The pilot valve 70 can be actuated electromagnetically and has an electromagnet 76 and a return spring 78 . The pressure line 26 leads via a branch to the pilot valve 70 . A pilot line 80 leads from the pilot valve 70 to the valve devices 40 , 40 ', 40 '', 40 '''.

If the pilot valve 70 is in the symbolic position 74 , pressure medium can flow out of the pilot line 80 to the hydraulic tank of the pressure sink 12 . This means that in the functional position 74 of the pilot valve 70, the pilot line 80 is relieved of pressure. When the electromagnet 76 is sufficiently energized, the pilot valve 70 is in the actuation position 72 , and when the electromagnet 76 is not energized, the return spring 78 ensures that the pilot valve 70 is in the symbolically represented functional position 74 .

The pilot valve 70 is in the actuating position 72 shown symbolically, so pressure medium can flow from the pressure line 26 into the pilot line 80 , whereby line 80 a pilot pressure can build up in the pilot line.

The valve device 40 is constructed so that a pressure in the Lei device 58 strives to bring the valve device 40 into the symbolic position 44 shown. The pressure in the pre-control line 80 strives to switch the valve device 40 into the actuating position 42 . When the pressure source 10 is switched on and the pilot valve 70 is in the actuation position 72 , the pressure in the pilot line 80 can actuate the valve device 40 in the actuation position 42 . The pilot pressure in the pilot line 80 acts in the same way on the other valve devices 40 ', 40 '', 40 '''. All valve devices 40 , 40 ', 40 '', 40 ''' can be operated with a single pilot valve 70 , which significantly reduces the number of electromagnets required. This also reduces the consumption of electrical power or energy.

The actuators 2 , 2 ', 2 '', 2 ''', the control valves 20 , 20 ', 20 '', 20 ''', the storage elements 50 , 50 ', 50 '', 50 ''' and 52 , 52 ', 52 '', 52 ''' and the valve devices 40 , 40 ', 40 '', 40 ''' can be constructed essentially the same and connected in the same way, which is why the description of the description of the actuator because of the clarity 2 is restricted with the associated storage elements and valves.

The suspension system is controlled via one in the drawing Control electronics, not shown. From this control electronics lead electrical lines, not shown, to the actuatable Components of the suspension system and also not shown provided sensors and controls.  

If, for example, the control electronics determines with the aid of an input program that the suspension system is not working properly and / or if a relevant actuatable component is not functioning properly and / or if the drive of the pressure source 10 , which is not shown, is switched off and / or if the pressure source 10 fails, then the suspension system proposed here is brought into an actuation state, which can be described as the basic state. The proposed suspension system is designed so that the actuatable components are de-energized, ie automatically return to the basic state. The drawing shows the suspension system in the basic state.

In the basic state, the level control is switched off, the pressure control device 30 is inoperative and the suspension system works with increased spring stiffness and possibly also with greater damping.

The valve device 40 is such that in the symbolically represented functional position 44 , ie in the basic state, no pressure medium can flow from the direction of the actuator 2 and the second storage element 52 in the direction of the first storage element 50 or in the direction of the pressure control device 30 . It is not necessary that the valve device 40 can also block the reverse flow direction because the control valve 20 in the first actuating position 21 , ie in the basic state, the line 46 leading to the valve device 40 relieves pressure. As a result, a simple-construction, expedient and tightly closing valve can be used for the valve device 40 , which is explained in more detail further below in special exemplary embodiments. However, the valve device 40 can also be designed so that in the functional position 44 , ie in the basic state, the reverse flow direction, ie from the direction of the line 46 in the direction of the lines 48 and 58 , is blocked.

In the embodiment shown in FIG. 1, several advantageous further developments of this suspension system are shown in addition to the actual suspension system according to the invention. In this exemplary embodiment, at least in the controlled driving state, a particularly safe, comfortable driving behavior of the vehicle that meets the highest demands is obtained. Good driving behavior is still achieved even if the level control or the pressure control device 30 fails. This driving behavior corresponds to that of a conventional, passive suspension system.

With the level control switched on and if the Drucksteuereinrich device 30 is working properly, then the valve device 40 , the relief valve 66 and the pilot valve 70 are switched to their actuation positions 42 , 67 , 72 and the control electronics (not shown) can, depending on the currently desired movement of the piston rod 8 or the cylinder 4 , control the control valve 20 of the pressure control device 30 accordingly. Depending on the control valve 20 is shifted more in the first operation position 21 or more in the third operating position 23, is used to Aktua tor 2 pressure medium supplied to or from the actuator 2 printing medium from behind. The actuators 2 , 2 ', 2 ''and 2 ''' can be operated independently of each other.

If the requirements are less stringent, the suspension system according to the invention can also be embodied in a simplified embodiment. Approximate shape depending on a correspondingly simplified exporting FIGS. 2 and some of the subsequent figures.

Fig. 2 shows a further advantageous embodiment of the suspension system.

In all figures, the same or equivalent parts are provided with the same reference numerals. The following exemplary embodiments are largely constructed in the same way as the first exemplary embodiment according to FIG. 1, with the exception of the deviations essentially specified below. Details of the various exemplary embodiments can be combined with one another.

In Fig. 2, the actuators 2 ', 2 '', 2 ''' with the associated memory and control valves 20 ', 20 '', 20 ''' are not shown for better clarity. The Fig. 2 also shows only the pressure source 10 and the control valve 20 for better clarity of the pressure control device 30 substantially.

The valve device 40 of the exemplary embodiment shown in FIG. 2 can be actuated electromagnetically. Is the electromag net energized and the valve device 40 is in the actuation position 42 , the pressure medium can flow through the Ventileinrich device 40 essentially unthrottled back and forth between the working space 32 of the actuator 2 and the storage space 50 a of the storage element 50 . Also, between the working chamber 32 and the SpeI cherraum 52 a of the storage element 52, the pressure in the medium we sentlichen unthrottled way herströmen. In the actuation position 42 , both storage elements 50 and 52 of the storage system 55 are effective. This gives the actuator 2 relatively soft suspension properties, which leads to comfortable driving. With the control valve 20 , pressure medium can be directed from the pressure source 10 to the working space 32 of the actuator 2 or can be discharged from the working space 32 into the pressure sink 12 , depending on the switching position of the control valve 20 . Pressure medium also flows into or out of the two storage spaces 50 a, 52 a, which leads to the soft suspension.

If the electromagnet of the valve device 40 is not energized, the valve device 40 is in the symbolically represented position 44 . In this functional position 44 , the storage space 50 a of the first storage element 50 is hydraulically clamped. This means that only the second storage system 52 can influence the spring properties of the actuator 2 , the spring stiffness of which is considerably harder than when the valve device is in the actuating position 42 .

If the rapid level control (SNR) is not ready for some reason, then the electromagnets of the Steuererven valve 20 and the valve device 40 are switched off. That is, the first storage element 50 is hydraulically disconnected and the control valve 20 is in an actuation position in which all connections of the control valve 20 are blocked. In other words, no pressure medium can get into the actuator from the pressure source 10 and no pressure medium can get out of the actuator 2 in the direction of the pressure sink. In this case, the suspension system works with much greater spring stiffness.

There is also a throttle 36 between the working space 32 and the second working space 34 . This throttle 36 can be made controllable in such a way that the damping in the energized state is smaller than in the de-energized state. The suspension system is designed so that when the fast level control is not ready for operation, or when the pressure control device is not working properly, not only the solenoid valves of the control valve 20 and the Ventilein device 40 are de-energized, but in addition, the power supply can also the adjustable throttle 36 are interrupted. This has the consequence that z. B. in the event of failure of the pressure control device 30 not only the spring stiffness, but also the damping is increased. This enables the vehicle to continue driving with almost no restrictions.

If the vehicle drive motor is switched off or the pressure control device 30 does not work or works insufficiently for another reason, then the control valve 20 and the valve device 40 are in the switching positions in which all connections of these valves are blocked. You can now dimension the second storage system 52 so that the spring stiffness of the suspension system is so great that the vehicle body rises or falls at most insignificantly when the load changes and the driving behavior corresponds to that of a conventional, passive suspension system. If one executes the control valve 20 and the valve device 40 in such a way that a good tightness is aimed at in the closed position, then the structure scarcely lowers even after a long standstill.

Fig. 3 shows a further developed, advantageous embodiment example of the suspension system.

So that in the embodiment shown in FIG. 2, the structure does not slowly sink when the vehicle drive motor is switched off, the control valve 20 must be tight in its central position, ie in the second actuation position 22 . Therefore, in the manufacture of the control valve 20 for the embodiment shown in FIG. 2, considerable effort is required, or a previously available proportional valve can hardly be used. Therefore, in the embodiment shown in FIG. 3, the valve device 40 is designed such that in the non-energized state there was also no pressure medium from the working space 32 of the actuator 2 and also not from the second storage element 52 in the direction of the control valve 20 . Preferably, one can use a poppet valve for the Ven tileinrichtung 40 , so that excellent tightness is guaranteed. The control valve 20 is preferably de-energized in the first actuation position 21 , in which the connection side of the valve device 40 facing the control valve 20 is relieved of pressure.

Since there are no special requirements for the tightness of the control valve 20 in this and in the following exemplary embodiments, the use of a proportional valve is very accommodating.

FIG. 4 shows a further advantageous embodiment.

Compared to the embodiment shown in FIG. 3, in the suspension system shown in FIG. 4, the first storage element 50 with its storage space 50 a is connected to the line 46 between the control valve 20 of the pressure control device 30 and the valve device 40 . This has the advantage over the embodiment shown in FIG. 3 that the Ventilein device 40 has to be equipped with fewer connections and also builds much simpler and smaller.

Fig. 5 shows another, particularly advantageous embodiment example.

As explained with reference to the embodiment shown in FIG. 2, it is useful if, for. B. in the event of failure of the pressure control device 30 , the throttle 36 passes into a state of greater damping. Therefore, it may be necessary in the exemplary embodiment shown in FIG. 2 to perform the throttle 36 in an adjustable manner, which requires a certain amount of production.

In the suspension system shown in FIG. 5, compared to the exemplary embodiments explained with reference to FIGS. 2 to 4, the throttle 60 is interposed between the working space 32 and the second storage element 52 when the valve device 40 is in its functional position 44 . In other words, if in this exemplary embodiment shown in FIG. 5 the valve device 40 switches from the actuating position 42 into the symbolically illustrated functional position 44 , then not only is the spring stiffness increased, but also the damping, since now that between the Ar beitsraum 32 and the second storage element 52 exchanging pressure medium in the functional position 44 must flow through the throttle point 60 .

Fig. 6 shows a further advantageous embodiment of the suspension system.

In the exemplary embodiment shown in FIG. 5, the pressure medium is throttled in the same way by the throttle point 60 both in the retracting stroke and in the extending stroke. There are cases in which it is advantageous if, in the event of failure of the pressure control device 30, the throttle point 60 operates in such a way that the throttling of the pressure medium is different from the retracting stroke when the actuator 2 is extended. Therefore, in the example shown in FIG. 6, the throttle body 60 includes the retracting throttle 60 a and the extending throttle 60 b, which are designed so that only the retracting throttle 60 a during the retracting stroke and only the extending throttle 60 b during the extending stroke of the actuator 2, the throttling of the print medium. This can be done in that, as shown in Fig. 6, the throttle position 60 is divided into two parallel branches, each of the two branches each containing a check valve which is switched so that only one of the throttles 60 a in each direction or 60 b can be flowed through.

Fig. 7 shows a further embodiment.

Figs. 2 to 6 show embodiments in which the Ven tileinrichtung 40 is actuated electromagnetically directly. In a four-wheel vehicle, the valve device 40 is normally required four times. This requires an equal number of electromagnets for actuating the valve device 40, which is present several times. In the embodiment shown in FIG. 7, the valve device 40 is controlled hydraulically. This is done with the help of the pilot valve 70 . The pilot valve 70 is connected in the same manner as in the embodiment shown in FIG. 1 and explained with reference to FIG. 1. This has the advantage that even if there are several actuators, only a single pilot valve 70 with a single electromagnet 76 is required.

Fig. 8 shows a further, particularly advantageous embodiment example of the suspension system.

As shown in FIG. 7, when the electromagnet is not energized, the storage space 50 a of the first storage element 50 is relieved of pressure toward the pressure sink 12 . When starting up the suspension system could play in the Ausführungsbei shown in FIGS. 4 to 7 possibly a large amount of pressure medium flow into the first Speicherele element 50 , which can possibly lead to hard switching shocks and to the fact that the hydraulically operated valve device 40 temporarily does not work properly. To avoid this, a control passage 82 is provided in the embodiment shown in FIG. 8. This branches off between the pilot control valve 70 and the valve device 40 from the pilot control line 80 and leads through the valve device 40 into the line 46 connected to the first storage element 50 .

While the pressure control device 30 is not working, ie when the level control is not ready for operation, the valve device 40 is in the functional position 44 . When the level control is started up, the control valve 20 is switched into the actuation position 22 and the pilot valve 70 into the actuation position 72 . The valve device 40 initially remains in the functional position 44 and pressure medium can flow out of the pilot line 80 via the control passage 82 into the first storage element 50 and build up a pressure in this. If the pressure in the storage system 50 has reached a certain value, which is dependent on the pressure in the line 48 , and the pressure in the pilot line 80 continues to increase, then the valve device 40 switches from the functional position 44 to the actuating position 42 . In the actuation position 42 , the control passage 82 between the pilot line 80 and the first storage element 50 is closed, so that the full system pressure supplied by the pressure source 10 can act in the pilot line 80 .

In Fig. 9, another advantageous embodiment is provided.

In the embodiment shown in FIG. 9, a spring 84 is provided. The spring 84 acts in such a way that the valve device 40 is clearly in the symbolically illustrated functional position 44 even in the unpressurized state. Also, the pressure in the working chamber 32 and the pressure in the storage spaces 52 a, 52 b, 52 c of the second memory element 52 is also striving to the valve means term betae 40 in the direction indicated with 44 the functional position. Therefore, to actuate the valve device 40 in the actuating position 42, the pressure in the pilot line 80 must be at least greater by the amount that the additional force caused by the spring 84 can overcome. To achieve this, a preload valve 86 is provided in the valve device 40 in the course of the control passage 82 . The gas flowing from the pilot line 80 into storage element 50 pressure medium must flow over this biasing valve 86, which is why the pressure in the pilot line 80 accordingly the evoked by the bias valve 86 Druckdif conference is greater. So that the valve device 40 has in each operating state Be a precisely defined switching position. This is special DERS advantageous if the level control is set while driving in radio tion because by the compression and rebound of the actuator 2 in the line 48 pressure fluctuations occur.

Fig. 10 shows another advantageous embodiment of the suspension system according to the invention.

In the exemplary embodiments shown in FIGS . 1 to 9, the actuator 2 is a separating cylinder with the two working spaces 32 , 34 and the throttle 36 between them in the working spaces 32 , 34 . Instead of a separating cylinder, a so-called plunger cylinder can also be used as actuator 2 , as shown in FIG. 10. This actuator 2 has only one working space 32 .

In order to achieve sufficient damping of the suspension system even when using a plunger cylinder, in the course of the connection 38 between the working space 32 and the first storage element 50, a throttle 88 and / or in the course of the line 58 between the working space 32 and the second storage element 52 a throttle 90 can be provided. The restrictor 60 is clauses to the Dros 88, 90 adjusted such that when in the operative position 44 is located Direction valve means 40, the attenuation is larger than that when the valve means is in the actuated position 42 40th

In Fig. 11 you can see another, advantageous game Ausführungsbei.

FIG. 11 shows a particularly simple, advantageous way of realizing the valve means 40. Here, the valve device 40 comprises a housing 92 with a valve seat 94 provided on the housing 92 , a valve chamber 96 , a valve body 98 and an actuator 100 . The valve body 98 is axially displaceably mounted within the Ven tilraums 96 . The lines 46 , 48 , 58 and the pilot line 80 lead via corresponding connections 46 a, 48 a, 58 a, 80 a into the housing 92 of the valve device 40 .

The actuator 100 includes a piston 102 . The connection 80 a of the pilot line 80 is inserted into the housing 92 so that the pressure supplied via the pilot line 80 in a control pressure chamber 104 can act on the piston 102 of the actuator 100 . The pressure in the control pressure chamber 104 generates a force acting on the valve body 98 in the opening direction via the piston 102 . There is a space 108 on the end face of the piston 102 facing away from the control pressure space 104 . A passage 106 leads through the piston 102 from the control pressure chamber 104 into the chamber 108 . An outlet 110 leads from the space 108 into the line 46 or into the first storage element 50 .

The exemplary embodiment shown in FIG. 11 corresponds approximately to the exemplary embodiment shown symbolically in FIG . The valve device 40 is shown in FIG. 11 so that the valve device 40 is in the position indicated in FIG. 8 with the functional position 44 . The control passage 82 extends through the control pressure chamber 104 , through the passage 106 and through the outlet 110 . In the gig. 11 position shown, the control passage 82 is opened from the pilot valve 70 to the storage element 50 .

When the level control is not ready for operation or is switched off, the valve body 98 bears against the valve seat 94 . Thus, no pressure medium can flow from the actuator 2 to the pressure sink 12 and also no pressure medium from the two-th storage element 52 in the direction of the pressure sink 12 . Since the valve device 40 is designed as a seat valve, very good tightness is ensured. Because in the switched-off state, in addition to the pilot valve 70 , the control valve 20 is also de-energized, the line 46 is depressurized, which ensures that no pressure medium can flow from the pressure source 10 or from the first storage element 50 in the direction of the actuator 2 . This has the desired effect that the actuator 2 works reliably with greater spring stiffness and any loss of pressure medium from the actuator 2 is prevented even when the vehicle is at a standstill for a long time.

The valve body 98 has an indentation or annular groove with a small cross section on its cylindrical outer circumference. The connections 48 a, 58 a of the lines 48 and 58 are guided through radial bores in the Ven tilraum 96 . In the position shown in FIG. 11 and designated in FIG. 8 with the functional position 44 , the recess arranged on the outer circumference of the valve body 98 covers the connections 48 a, 58 a, so that between the working space 32 and the second storage element 52 Exchanging pressure medium must flow through the circumferential annular groove. Because of the small cross section of this annular groove, the throttle point 60 is formed , the part effect of which has already been explained with reference to FIG. 8.

When commissioning the level control, e.g. B. when starting the driving tool drive motor of the vehicle, the system pressure is built up by the pressure source 10 in the pressure line 26 . The control valve 20 is first brought into the second actuation position 22 , in which all connections of the control valve 20 are closed. The electric magnet 76 of the pilot valve 70 is energized. As a result, the pilot valve 70 switches to the actuation position 72 and pressure medium flows via the pilot valve 70 through the pilot line 80 into the control pressure chamber 104 . Via the passage 106 and the outlet 110 of the control passage 82 , pressure medium flows into the line 46 and fills the storage space 50 a of the first storage element 50 with pressure medium. Together with the pressure increase in the storage element 50 , the pressure in the control pressure chamber 104 of the actuator 100 also increases . As soon as the pressure in the control pressure chamber 104 has reached a size which is sufficient to overcome the force caused by the pressure prevailing in the second storage element 52 or in the working chamber 32 of the actuator 2 , the piston 102 moves in the direction of the valve body 98 and lifts the valve body 98 from the valve seat 94 . The piston 102 is actuated so far in the opening direction until the piston 102 comes to rest on a circumferential sealing edge 114 provided on the housing 92 . The passage 106 projects inside the sealing edge 114 and the outlet 110 projects outside the sealing edge 114 into the space 108 . Due to the abutment of the piston 102 on the sealing edge 114 , the control passage 82 is closed, so that no pressure medium can flow out of the control pressure chamber 104 . The full system pressure provided by the pressure source 10 can thus act in the control pressure chamber 104 . Now the Ventileinrich device 40 is in the position designated in FIG. 8 with the actuating position 42 . In this position, the valve body 98 has lifted so far from the valve seat 94 that an unimpeded exchange of the pressure medium takes place between the connections 46 a, 48 a, 58 a, ie between the actuator 2 , the storage elements 50 , 52 and the control valve 20 can. Now you can set the control valve 20 more or less far in the desired actuation position 21 , 22 , 23 ver and accordingly the actuator 2 between the vehicle structure and the wheel carrier can exert forces. That is, the level control is ready for operation again and the pressure control device 30 works again.

Via a control line 112 , the second storage element 52 is connected to the valve chamber 96 , so that the pressure prevailing in the storage spaces 52 a, 52 b can act on the valve body 98 in the closing direction. Like the next figure, FIG. 12, the control line 112 can also be guided in such a way that the pressure prevailing in the line 48 or in the working space 32 of the actuator 2 acts on the valve body 98 .

Fig. 12 shows a further embodiment.

The exemplary embodiment shown in FIG. 12 largely corresponds to that of FIG. 11, with the following essentially specified deviations. The suspension system shown in FIG. 12 works largely as it was explained earlier with reference to the embodiment shown in FIG. 9.

An exemplary embodiment is shown in FIG. 12, in which the valve body 98 always assumes a precisely defined position. This is done with the aid of the spring 84 acting on the valve body 98 in the closing direction. In this valve means 40 which provides in the passage 106 between the control pressure chamber 104 and the space 108 is arranged biasing the valve 86 for a certain differential pressure between the control pressure chamber 104 and the space 108 during the switching of the level control. In other words, when the level control is started up, the pressure in the control pressure chamber 104 is higher than in the chamber 108 by an amount determined by the preload valve 86 . The bias valve 86 may be in the form of a check valve slightly biased by a spring.

The passage 106 opens into a port 106 a in the room 108 . If the piston 102 is actuated in the opening direction after the level control has been started, the piston 102 closes the connection 106 a and in the control pressure chamber 104 the full system pressure generated by the pressure source 10 can form.

FIG. 13 is a further embodiment again.

Compared to the previously described exemplary embodiments, a sealing element 116 is arranged on the valve body 98 in the exemplary embodiment shown in FIG. 13. The sealing element 116 is preferably made of a circumferential, rubber-elastic plastic. Ses sealing element 116 is in the closed state on the valve seat 94 of the housing 92 . This ensures a particularly excellent seal.

You can also modify the embodiment of FIG. 13 so that the elastic sealing element 116 is not connected to the valve body 98 , but is arranged on the housing 92 in the region of the valve seat 94 .

The throttle point 60 shown in FIG. 13 is formed in the course of a bore leading through the valve body 98 by providing a constriction in the course of this bore. This bore extends through the valve body 98 in such a manner that, that is, when the valve body 98 abuts when in ge connected position, befindendem valve body 98 at valve seat 94, the two terminals 48 a, 58 are connected to each other through this hole a. To ensure this, an anti-rotation device, not shown in the drawing, is provided for the valve body 98 . The anti-rotation device is unnecessary when attaching a ring recess, as shown in FIGS. 11, 12, 14, 15.

The valve device 40 can be designed so that no or virtually no pressure medium can flow during the opening or closing of the free cross section between the valve body 98 and the valve seat 94 . This detail will be explained in more detail using the next embodiment shown in FIG. 14.

Fig. 14 shows another embodiment of the suspension system.

For the sake of clarity, only a section of the valve device 40 is shown in a modified scale in FIG. 14.

With this valve device 40 there are two sealing points 121 , 122 provided one behind the other in the course of the possible connection between the connection 46 a and the connection 48 a or 58 a. The sealing points 121 , 122 are formed in the interaction of the sealing body 98 with the housing 92 . The elastic sealing element 116 is located in the area of the sealing point 121 . The sealing point 122 is designed like a gap seal. If the valve body 98 is in its closed position shown in FIG. 14, then there is only a very narrow gap between the valve body 98 and the housing 92 in the area of the sealing point 122 , similar to what is common with good slide valves. The narrow gap is formed by an overlap 123 extending in the actuating direction between the valve body 98 and the housing 92 . In the closed position, the sealing elements 116 arranged in the region of the sealing point 121 on the valve body 98 lie against the valve seat 94 of the housing 92 . Since you get in the area of the seal 121 as good as absolute tightness.

If the valve body 98 is actuated in the opening direction (upwards in FIG. 14), the sealing element 116 first lifts off the valve seat 94 . That is, the sealing point 121 opens first. Initially, the sealing point 122 remains closed because of the overlap 123 between the valve body 98 and the housing 92 . Therefore, at most a very insignificant amount of pressure medium can flow between the sealing element 116 and the valve seat 94 during the opening process. During opening there is only the pressure difference caused by the spring 84 between the connection 46 a and the connections 48 a and 58 a. Only when the elastic sealing element 116 has lifted relatively far from the valve seat 94, the sealing point 122 opens the passage between the connections 46 a and 48 a or 58 a, so that only now can the pressure medium flow back and forth.

In the opposite direction, ie when the valve body 98 moves in the closing direction (downwards in FIG. 14), the sealing point 122 is first closed and only then does the elastic sealing element 116 come into the region of the valve seat 94 .

Since the valve device shown in FIG. 14 always closes first the sealing point 122 in the form of a gap seal and then only the sealing point 121 with the elastic sealing element 116 , or because the elastic sealing element 116 always lifts off the valve seat 94 before the sealing point 122 opens, larger flow forces damaging the elastic sealing element 116 can never occur in the area of the sealing point 121 . The valve device 40 is designed so that with large forces acting on the Ventilkör by 98 in the closing direction, after a certain elastic, harmless deformation of the sealing element 116 , the valve body 98 outside the actual sealing point 121 on the housing 92 comes into metallic contact. This protects the sealing element 116 from any inadmissible deformation. A long durability of the elastic sealing element 116 is ensured by the measures described above.

In the proposed valve device 40 , it does not matter which of the two sealing points 121 , 122 is arranged in relation to the flow direction before the other sealing point.

In Fig. 15 it can be seen, for example, a further advantageous execution.

As shown in reference to the Fig. 7 embodiment he explained, can b divide the throttle point 60 in a competent for retraction of the actuator 2 Einfahrdrossel 60 a and into a competent for extension of the actuator 2 Ausfahrdrossel 60. Fig. 15 shows a particularly advantageous embodiment, as one can realize the division of the orifice 60 in the inductors 60 a, 60 b when the valve device 40 is advantageous.

In the housing 92 of the valve device 40 there is a groove 148 a and a groove 158 a. There is also a groove 148 b and a groove 158 b in the valve body 98 . The Nutein stitches 148 a, 148 b correspond to the lead to the actuator 2 , the terminal 48 a and the groove punctures 158 a, 158 b correspond to the terminal 58 a leading to the memory element 52 .

A passage 124 is provided between the groove puncture 148 b and the groove puncture 158 b. A biased by a spring 128 against the passage 124 valve plate 126 blocks the path of the pressure medium from the groove 158 b in the direction of the groove 148 b, but from the groove 148 b in the direction of the groove 158 b can throttled accordingly the pressure medium. The passage 124 , the valve plate 126 and the spring 128 belong to the throttle 60 a. Correspondingly, there is a passage 134 , as well as a valve plate 136 and a spring 138, between the groove recesses 148 b, 158 b. These are part of the extension throttle 60 b and only permit a correspondingly throttled flow of pressure medium during an extension stroke of the actuator 2 .

If the valve body 98 is actuated in the closing direction (as shown in FIG. 15), that is to say if the valve device 40 is in the position designated by functional position 44 in FIG. 7, then the pressure medium can be moved through the intake throttle 60 a during an insertion stroke stream. It is throttled by the valve plate 126 in the desired manner. During an extension stroke, the pressure medium can flow from the storage element 52 through the line 58 and through the extension throttle 60 b into the actuator 2 . It is throttled by the valve plate 136 of the extension throttle 60 b in a predeterminable manner.

One can also provide only one of the two throttles 60 a, 60 b, so that the pressure medium in the region of the throttle point 60 is throttled only during the driving stroke or only during the extending stroke. The throttle point 60 or the throttles 60 a, 60 b can be any way out and have any desired damping characteristics. The damping characteristic is preferably chosen so that when the level control is not ready for operation, ie when the pressure control device 30 does not work or does not work adequately, the damping and thus the driving behavior of the suspension system is no worse than a conventional, passive suspension system. Plate valves can be used as throttles 60 a, 60 b.

When the valve body 98 is actuated in the opening direction, which is denoted by actuation position 42 in FIG. 7, the pressure medium can flow back and forth between the connections 46 a, 48 a, 58 a via the groove recesses 148 a, 158 a, 158 b. There is no damping by the throttle point 60 , or the throttles 60 a, 60 b are out of function.

As already mentioned, the memory system 55 comprises a plurality of memory elements 50, 52, wherein the second storage element 52 may be biased try a different biasing pressure than the first storage element 50th In addition, it is possible to provide the storage element 50 and / or the storage element 52 with a plurality of storage spaces 50 a, 50 b etc. and 52 a, 52 b etc., respectively. It is possible to preload the gas space of these storage spaces with different gas pressure. This allows the suspension characteristics of the suspension system to be adapted very precisely and easily to the respective requirements.

Claims (38)

1. Suspension system for vehicles with at least one actuator between a vehicle body and a wheel carrier which rotatably carries a wheel and in which the actuator comprises at least one working space containing a pressure medium for variable working pressure, the working space having a storage system which influences a spring stiffness of the suspension system and is connected to a Drucksteuerein device for supplying pressure medium in the work space and removal of pressure medium from the work space, characterized in that means ( 40 , 70 ) are provided which are designed in such a way that the pressure in the case of inadequate work control device ( 30 ) the spring stiffness of the suspension system is increased. 2. Suspension system according to claim 1, characterized in that said means comprise a valve device ( 40 ), the size of the storage system ( 50 , 52 ) which is effective for the spring stiffness being changeable by the valve device and the valve device ( 40 ) designed in this way is that in a functional position ( 44 ) of the valve device ( 40 ) the effective size of the storage system ( 50 , 52 ) is reduced. 3. Suspension system according to claim 2, characterized in that the valve device ( 40 ) comes into said functional position ( 44 ) when not actuated. 4. Suspension system according to claim 2 or claim 3, characterized in that the storage system ( 55 ) comprises a first storage element ( 50 ) and at least a second storage element ( 52 ), the valve device ( 40 ) being designed in such a way that in said functional position ( 44 ) of the valve device ( 40 ), a flow of pressure medium from the working space ( 32 ) in the direction of the first storage element ( 50 ) is prevented. 5. Suspension system according to one of claims 2 to 4, characterized in that the valve device ( 40 ) in the course of the connec tion ( 38 ) between the working space ( 32 ) and the Drucksteuereinrich device ( 30 ) is arranged and designed so that at in said functional position ( 44 ) of the valve device ( 40 ), a flow of pressure medium from the working space ( 32 ) in the direction of the pressure control device ( 30 ) is prevented. 6. Suspension system according to claim 5, characterized in that the first storage element ( 50 ) of the connection ( 46 ) between the pressure control device ( 30 ) and the valve device ( 40 ) is assigned net. 7. Suspension system according to one of claims 2 to 6, characterized in that a throttling ( 60 , 60 a) for the pressure medium flowing from the working space ( 32 ) is provided, which is in said functional position ( 44 ) located valve device ( 40 ) is activated by the valve device ( 40 ). 8. Suspension system according to one of claims 2 to 7, characterized in that a throttling ( 60 , 60 b) is provided for in the working space ( 32 ) flowing pressure medium, which is located in said functional position ( 44 ) valve device ( 40 ) is effectively switched. 9. Suspension system according to claim 4 and claim 7 and / or claim 8, characterized in that in said function set ting ( 44 ) located valve device ( 40 ), the throttling ( 60 , 60 a, 60 b) in the course of the connection ( 48 , 58 ) between the working space ( 32 ) and the second storage element ( 52 ) is effective. 10. Suspension system according to one of claims 2 to 9, characterized in that the valve device ( 40 ) via a pilot valve ( 70 ) can be actuated fluidically. 11. Suspension system according to claim 10, characterized in that a plurality of valve devices ( 40 , 40 ', 40 '', 40 ''') can be actuated by a common pilot valve ( 70 ). 12. Suspension system according to claim 11, characterized in that the suspension system has a plurality of actuators ( 2 , 2 ', 2 '', 2 ''') and a plurality of valve devices assigned to the actuators ( 40 , 40 ', 40 '', 40 ''') Comprises, wherein all valve devices are actuated by a single before control valve ( 70 ). 13. Suspension system according to one of the preceding claims, characterized in that in the case of inadequate work of the pressure control device ( 30 ) a pressure control device ( 30 ) pressure-relieving relief valve ( 66 ) is arranged. 14. Suspension system according to one of claims 2 to 12, characterized in that the pressure control device ( 30 ) comprises a pressure source ( 10 ), a pressure sink ( 12 ) and a control valve ( 20 ), the control valve ( 20 ) being formed in such a way is that in an unactuated basic position ( 21 ) of the control valve ( 20 ) a flow of pressure medium from the direction of the valve device ( 40 ) in the direction of the pressure sink ( 12 ) is possible. 15. Suspension system according to one of claims 2 to 12, characterized in that the pressure control device ( 30 ) comprises a pressure source ( 10 ), a pressure sink ( 12 ) and a control valve ( 20 ), the control valve ( 20 ) being formed in such a way is that in an un-actuated basic position ( 21 ) of the control valve ( 20 ) a flow of pressure medium from the first storage element ( 50 ) in the direction of the pressure sink ( 12 ) is possible. 16. Suspension system according to claim 14 and / or 15, characterized in that the control valve ( 20 ) is controlled in such a way that in the inadequate work of the pressure control device ( 30 ) from the control valve ( 20 ) the basic position ( 21 ) is assumed . 17. Suspension system according to claim 4, characterized in that the valve device ( 40 ) comprises a valve seat ( 94 ), a valve body ( 98 ), a valve chamber ( 96 ) and an actuator ( 100 ) for actuating the valve body ( 98 ), wherein the Working space ( 32 ) and the first storage element ( 50 ) on the valve device ( 40 ) are connected in such a way that when the actuator ( 100 ) is not actuated, the valve body ( 98 ) is actuated against the valve seat ( 94 ), with which the flow of pressure medium from the working space ( 32 ) in the direction of the first storage element ( 50 ) is prevented. 18. Suspension system according to claim 17, characterized in that when the actuator ( 100 ) is not actuated, the valve body ( 98 ) is acted upon in the closing direction by the pressure prevailing in the working space ( 32 ) of the actuator ( 2 ). 19. Suspension system according to claim 17 or 18, characterized in that the valve body ( 98 ) is acted upon by an elastic element ( 84 ) in the closing direction. 20. Suspension system according to one of claims 17 to 19, characterized in that the second storage element ( 52 ) on the valve device ( 40 ) is connected, with a throttling ( 60 , 60 ) when actuated against the valve seat ( 94 ) valve body ( 98 ) a, 60 b) for between the working space ( 32 ) and the second storage element ( 52 ) exchanging pressure medium is activated at least for one of the two possible flow directions. 21. Suspension system according to claim 20, characterized in that the valve device ( 40 ) comprises at least one damping throttle valve ( 126 , 136 ) which produces the throttling. 22. Suspension system according to claim 20 or 21, characterized in that the throttling ( 60 a, 60 b) of the pressure medium is different in size for the two flow directions. 23. Suspension system according to one of claims 17 to 22, characterized in that the actuator ( 100 ) comprises a piston ( 102 ) which can be acted upon with a control pressure and which, when acted on with a sufficiently large control pressure, the valve body ( 98 ) from its valve seat ( 94 ) can take off. 24. Suspension system according to claim 23, characterized in that the pressure medium forming the control pressure can flow through a control passage ( 82 ) into the first storage element ( 50 ). 25. Suspension system according to claim 24, characterized in that in the control passage ( 82 ) a pressure medium throttling bias valve ( 86 ) is arranged. 26. Suspension system according to claim 24 or 25, characterized in that the control passage ( 82 ) through the piston ( 102 ). 27. Suspension system according to one of claims 24 to 26, characterized in that the control passage ( 82 ) is closed when the valve body ( 98 ) is actuated in the opening direction by the piston ( 102 ). 28. Suspension system according to claim 27, characterized in that the control passage ( 82 ) can be closed by adjusting the piston ( 102 ). 29. Suspension system according to one of claims 23 to 28, characterized in that the control pressure can be controlled with the aid of a pilot valve ( 70 ). 30. Suspension system according to claim 29, characterized in that the pilot valve ( 70 ) is designed and electrically controlled in such a way that if the pressure control device ( 30 ) does not work adequately, a passage through which the piston ( 102 ) acts upon the control pressure the pilot valve ( 70 ) is released in the direction of the pressure sink ( 12 ). 31. Suspension system according to claim 29 or 30, characterized in that the control pressure for the actuators ( 100 ) of a plurality of Ven valve devices ( 40 , 40 ', 40 '', 40 ''') can be controlled by a common pre-control valve ( 70 ) . 32. Suspension system according to one of claims 17 to 31, characterized in that in the region of the valve device ( 40 ) between the connection ( 48 a) of the working space ( 32 ) and the connection ( 46 a) of the first storage element ( 50 ) or Pressure control device ( 30 ) two series-connected sealing points ( 121 , 122 ) are provided, one of which is designed as a gap seal ( 122 ) and a second ( 121 ) seals by elastic preforming, with only partially open passage between the connections ( 46 a , 48 a), a free passage cross section in the area of the sealing point ( 122 ) formed as a gap seal is smaller than a free passage cross section in the area of the elastically sealing sealing point ( 121 ). 33. Suspension system according to claim 32, characterized in that in the region of the elastically sealing sealing point ( 121 ) between the valve body ( 98 ) and the valve seat ( 94 ) sealing elastic sealing element ( 116 ) is arranged. 34. Suspension system according to one of claims 4 to 33, characterized in that the two storage elements ( 50 , 52 ) each comprise a storage space ( 50 a, 52 a), these storage spaces being biased with different biasing pressures. 35. Suspension system according to one of claims 4 to 33, characterized in that at least one of the two storage elements ( 50 , 52 ) comprises a plurality of storage spaces ( 50 a, 50 b, 50 c, 52 a, 52 b, 52 c). 36. Suspension system according to claim 35, characterized in that these storage spaces ( 50 a, 50 b, 50 c, 52 a, 52 b, 52 c) are biased with at least two different biasing pressures. 37. Method for operating a suspension system for vehicles with at least one actuator between a vehicle body and a wheel carrier which rotatably carries a wheel and in which the actuator comprises at least one working space containing a pressure medium for variable working pressure, the working space having a spring stiffness of the suspension system influencing storage system and with a pressure control device for supplying pressure medium to the work space and discharging pressure medium from the work space is connected, characterized in that the spring stiffness of the suspension system is increased when the pressure control device ( 30 ) does not work properly. 38. The method according to claim 37, characterized in that when the pressure control device ( 30 ) is inadequate, the pressure medium exchanging between the working space ( 32 ) of the actuator ( 2 ) and the storage system ( 55 ) is additionally throttled in at least one direction of flow.