DE10349655A1 - Hydraulic spring with stabilizer function for axle of road vehicle has two cross-connected hydraulic units with large lower chambers and small upper chambers and air spaces above upper pistons - Google Patents

Abstract

The first (12) and second (14) hydraulic spring units have fasteners (44,46) at the top, pivoted on the vehicle bodywork. The piston rods (40,42) of the first, large pistons (32,34) are connected to the axle and pass through first ventilated air chambers (79). The third small pistons (52,54) are rigidly connected to the second large pistons (48,50) in each unit by piston rods (56,58). Springs (60,62) push the piston units (36,38) downward. There are air chambers (78) over the top pistons. First (16,20) and second (18,22) pressure chambers are cross-connected (24,25).

Description

The The invention relates to a hydraulic spring system with stabilizer function according to the preamble of claim 1 specified type.

generally known has the spring system as a generic term for the interaction of suspension springs, stabilizers and vibration dampers a row for the overall behavior of the suspension highly significant tasks too fulfill. Among other things, the spring system to the vehicle body and thus especially the occupants against unpleasant lifting, pitching and swinging vibrations as well as protect from shocks and thus contribute to the mechanical vibration comfort.

conventional Spring systems point beside this the suspension springs mechanically acting stabilizers, for example in the form of torsion torsion bars, on, the middle part rotatably on a supporting arrangement of the body the vehicle is mounted and their ends via intermediate levers on the wheel suspension an axle are mounted.

The Disadvantages of these mechanical or conventional stabilizers are the unfavorable load distribution and the tie rods with the resulting non-constant Stabilizer spring rate.

From the DE 197 19 029 A1 An adjustable hydraulic axle stabilizer for motor vehicles is known. This stabilizer no longer consists of bending or torsion elements, but of a hydraulic power transmission system. The hydraulic axle stabilizer has at each suspension of the vehicle axle on a double-acting hydraulic cylinder whose piston position is changed by the vertical movement of the wheel to the rest of the vehicle. The hydraulic chambers of the cylinders are the same size on both sides, so that the same force / displacement ratios are present in both directions. The two hydraulic cylinders are cross-linked with hydraulic lines, so that the vertical movement of a piston causes a rectilinear movement of the opposite piston and the associated wheel. In order to ensure an adjustability of the spring stiffness of the axle stabilizer, a branch to each of a further hydraulic cylinder is mounted on both hydraulic lines which connect the hydraulic chambers of the cylinder crosswise, which can be acted upon for the adjustability of the spring stiffness with a corresponding force.

When disadvantage here proves that the system only one has pure stabilizer function and thus only one alternative for conventional Represents stabilizers. Due to the missing suspension function is a use as a complete spring system excluded.

Of the Invention is based on the object, a hydraulic spring system with stabilizer function for an axle of a motor vehicle according to the preamble of the claim 1 specified type such that avoiding the mentioned disadvantages the spring system no separate, additional Stabilizers needed.

These The object is achieved by the characterizing features of claim 1 solved in conjunction with its generic features.

The under claims form advantageous developments of the invention.

Of the The invention is based on the finding that a combination of Spring and stabilizer function within a spring system Waiver of separate, additional Stabilizers possible.

For this purpose points the hydraulic spring system with stabilizer function for one axle a motor vehicle, a first and a second hydraulic unit on, each between the motor vehicle body and a suspension element are arranged. In the hydraulic units guided pistons limit in the two hydraulic units each have a first and a second pressure chamber, each filled with a hydraulic fluid. For force introduction in the hydraulic spring system, each hydraulic unit is in each case via a first piston rod connected to the suspension element. To one power transmission from a suspension to allow the remote side, the pressure chambers are the two hydraulic units each via a cross-connected arranged first and second pressure line with each other. According to the invention in each hydraulic unit, a first piston with its first engagement surface over the in the first pressure chamber located hydraulic fluid with a second attack surface a second piston in operative connection. The second piston is here Coupled with a third piston and forms with this one said piston unit, wherein within the piston unit of the third Piston with its third attack surface with that in the second Pressure chamber located hydraulic fluid is operatively connected and the piston unit over at least one spring element in the housing of the hydraulic units supported is.

In a simple manner, such a hydraulic spring system is realized, which includes both a suspension and a stabilizer function. Due to the piston unit formed by the second and third piston, both via the second piston with the first pressure chamber and is connected via the third piston with the second pressure chamber in operative connection, and the connection of the pressure chambers of the hydraulic units via a cross-over the forces acting on the system forces are divided in a fixed ratio to the spring elements of both hydraulic units, which in turn causes a motion-related feedback of the hydraulic spring system. Power distribution and feedback are followed by the decisive stabilizer effect of the hydraulic spring system.

authoritative Size for the described force distribution Here is the ratio the piston size inside the piston unit, so the area ratio between second and third attack surface. Around to ensure optimum force distribution is preferred the third attack surface of the third piston smaller than the second attack surface of the second Piston.

The Size of the first and second piston, so the first and second attack surface is from the chosen one Design of the axle-related spring system dependent, d. h. that accordingly the chosen one Design the first and second attack surface both the same size as well designed differently sized could be.

According to one embodiment the invention is in the piston unit of the second and third pistons arranged in series and the two pistons are via a second piston rod rigidly connected.

According to one another embodiment In the piston unit, the second piston is parallel to the third Plunger arranged and the two pistons are over a common floor area rigidly connected. The parallel arrangement is remarkable especially by the fact that in the axial direction a smaller building demand needed becomes.

Corresponding for the installation of the hydraulic spring system available installation space can the second and third attack surface the piston unit and the first engagement surface of the first piston both consecutively be arranged as well as side by side.

Around an invalid Deflection of the pistons and associated damage to the hydraulic units To prevent, is the axial movability of the first piston and the piston unit within the hydraulic units, respectively an upper and lower stop position limited.

to To avoid cavitation, the two stop positions are constructive arranged so that in the process of the first piston in the lower Stop position the piston unit its lower stop position not reached and thus arranged in the housing spring element still has a minimum pressure generating bias, so that in the first and second pressure chamber each still a certain minimum pressure is ensured.

Of the Installation of one or more spring elements in the hydraulic units can be done in different places. For example, the spring element in between the case and the second pressure chamber facing away from the surface of the piston unit formed Space, hereinafter referred to as the first Leerhubraum arranged become. Also conceivable is the arrangement of the spring element in the so-called intermediate space, ie in the between the housing and the surface of the piston unit facing away from the first pressure chamber Room.

According to one another embodiment The invention is at least one in the hydraulic units Damping element arranged. Corresponding to the spring element is an installation of the damper element to different positions within the hydraulic units possible: so can the damping element in the first Leerhubraum and / or in the space and / or in between the housing and the space of the first piston facing away from the first pressure chamber, hereinafter referred to as the second Leerhubraum be arranged.

Conceivable is also, in the first and / or second pressure line, a damping element to provide in the form of a throttle.

According to one another embodiment the invention, the two pressure lines via means are either short-circuited. Farther are at the first and / or second pressure line means for fluid volume displacement and / or at least one progression element that can be switched on and off and / or an on and off switchable memory arranged with hydraulic fluid.

The Arrangement of the various means, which are given below in their entirety Simplified also be called auxiliary units, has the Advantage that the hydraulic spring system thereby extended, having an "active chassis" corresponding functionality.

So is due to the short circuit possibility the two pressure lines now a decoupling of the two sides of the wheel possible, this eliminates the stabilizer effect of the spring system.

In addition, a one- or two-sided infeed or Remove hydraulic fluid into the hydraulic units. This allows, for example, a one- or two-sided increase in a vehicle axle.

The Means for fluid volume displacement allow within the hydraulic Federsystems a shift of hydraulic fluid from one axle to others and can u. a. For a left-right height compensation be used. The means for fluid volume displacement are in this case preferably in the form of a pump and / or an actuator and / or a sliding element educated.

About the Progression element leaves the stabilizer spring rate can be reduced in a targeted manner. Are several progression elements provided, they are preferably to be arranged in parallel. By the parallel connection of several progression elements which can be switched on and off with different spring and damping properties can be realize different stabilizer characteristics in a vehicle.

The necessary regulation / control of the hydraulic spring system and The additional units described above via several sensors in dependence various factors. When Influencing variables come Here, for example, the Kolbenverfahrweg, pressure, steering angle, Speed, brake pressure, yaw rate, wheel pressure or the like, in question.

Further Advantages, features and applications of the present Invention will become apparent from the following description in conjunction with the embodiments shown in the drawing.

The Invention will be described below with reference to the drawing Embodiment described in more detail.

In the description, in the claims and in the drawing are the ones listed in the list below the reference numbers used terms and associated reference numerals uses. Show it:

1 a schematic sectional view of a basic version of a hydraulic spring system with integrated stabilizer function;

2 a schematic sectional view of the spring system 1 with various accessories;

3 a schematic sectional view of the construction example of a hydraulic unit of the hydraulic spring system;

4 a schematic sectional view of another construction example of a hydraulic unit; and

5 a schematic sectional view of an embodiment of the hydraulic spring system for use for Bremsnickausgleich.

6 Diagram of a hydraulic unit of the spring system The in 1 represented more or less schematically and in its entirety by the reference numeral 10 designated hydraulic spring system with integrated stabilizer function for an axle of a motor vehicle substantially comprises in each case one of an axle side associated first and second hydraulic unit 12 . 14 , which are each arranged between the motor vehicle body and a suspension element.

The first hydraulic unit 12 is in a first pressure chamber 16 and a second pressure chamber 18 divided. Accordingly, the second hydraulic unit also has 14 a first and second pressure chamber 20 . 22 on. The pressure chambers 16 . 18 the first hydraulic unit 12 as well as the pressure chambers 20 . 22 the second hydraulic unit 14 are each with a hydraulic fluid 23 filled. Via a cross-connected first and second pressure line 24 . 26 stand the pressure chamber 16 . 22 and the pressure chamber 18 . 20 in contact with each other.

In the case 28 . 30 the two hydraulic units 12 . 14 are each a first piston 32 . 34 and a piston unit 36 . 38 guided. Via a first piston rod 40 . 42 are the two hydraulic units 12 . 14 each connected to the, not shown here for reasons of clarity, suspension element. The connection of the hydraulic units 12 . 14 to the motor vehicle is only schematically with the fasteners 44 . 46 indicated.

The arrangement of the hydraulic spring system 10 can be parallel to the damper strut using the same connection points. It can be mounted just as remote. In this case, however, wheel-side hydraulic cylinders or transmission gear are necessary by means of which the wheel movement with the first piston rod 40 . 42 be coupled.

In the hydraulic units 12 . 14 is the piston unit 36 . 38 behind the first piston 32 . 34 arranged.

In this case, the piston unit comprises 36 . 38 the two hydraulic units 12 . 14 each a second piston 48 . 50 and a third piston arranged in series therewith 52 . 54 , About a second piston pole 56 . 58 are the second pistons 48 . 50 and the third pistons 52 . 54 each rigidly connected.

The piston unit 36 . 38 the two hydraulic units 12 . 14 is in each case by means of a spring element 60 . 62 in the case 28 . 30 the hydraulic units 12 . 14 supported. For this purpose, the spring element 60 . 62 in one between the housing 28 . 30 and the first pressure chamber 16 . 20 opposite surface of the piston unit 36 . 38 formed space, subsequently simplified as a space 64 . 66 designated arranged.

The first piston 32 . 34 each stands over his the first pressure chamber 16 . 20 facing piston surface, first engagement surface A ₁ , and in the first pressure chamber 16 . 20 located hydraulic fluid 23 with the first pressure chamber 16 . 20 facing surface of the second piston 48 . 50 , second attack surface A ₂ , in operative connection.

The first and second engagement surface A ₁ , A _{2 of} the first piston 32 . 34 and the second piston 48 . 50 are the same size.

The one with the second piston 48 . 50 rigidly coupled third piston 52 . 54 stands with his second pressure chamber 18 . 22 facing piston surface, third attack surface A ₃ , with in the second pressure chamber 18 . 22 located hydraulic fluid 23 in active connection. The third attack surface A _{3 of} the third piston 52 . 54 is smaller than the second attack surface A _{2 of} the second piston 48 . 50 educated.

Now, for example, the hydraulic system 10 via one on the first piston rod 40 acting force F ₁ loaded on one side, so by means of the first pressure line 24 interconnected first pressure chambers 16 the first hydraulic unit 12 and the second pressure chamber 22 the second hydraulic unit 14 a force distribution of the introduced force F ₁ on the second piston 48 with its attack surface A _{1 of} the first hydraulic unit 12 and on the third piston 54 with its attack surface A _{3 of} the second hydraulic unit 14 , Because in the first hydraulic unit 12 the piston unit 36 the first and second pressure chambers 16 . 18 and in the second hydraulic unit 14 the piston unit 38 the first and second pressure chambers 20 . 22 rigidly coupled with each other, there are over the second pressure line 26 communicating pressure chambers 18 . 20 a feedback of the system. The energy of the piston movements is in each case in the spring elements 60 . 62 saved. Power distribution and feedback are followed by the relevant stabilizer effect.

The described force distribution is in this case of the ratio of the piston size within the piston unit 36 . 38 , So from the area ratio of the second attack surface A ₂ to the third attack surface A ₃ , depending.

For two-sided force entry into the two hydraulic units 12 . 14 is there between the pages the same interaction described. The forces are distributed in this case on the two spring elements 60 . 62

The system - 1 - works passively. It is assumed here that the system is tight and that there has been a correct initial filling. In-system sensors, especially pressure and displacement sensors, are needed when, as in 2 Outlined on additional elements-means leaks and height differences are to be compensated or set height to adjust.

To increase the functionality, such as the use as an "active chassis", the hydraulic system 10 out 1 , as in 2 shown to be extended by several additional units.

So are the first pressure chamber 16 . 20 and second pressure chamber 18 . 22 a hydraulic unit 12 . 14 via a valve control box 68 optionally short-circuitable. Furthermore, in the first and second pressure line 24 . 26 Means for fluid volume displacement and a plurality of arranged in parallel switching on and disconnectable progression elements available. Both the means for fluid volume shift as well as the on and off switchable progression elements are for reasons of clarity by an element 70 symbolically summarized. In addition, at the two pressure lines 24 . 26 each one on and off memory 72 with hydraulic fluid 23 and a throttle 74 arranged for stabilizer damping.

About the memory 72 there is the possibility of a one- or two-sided feed or removal of hydraulic fluid 23 , ie the axes of the motor vehicle can be raised or lowered one or both sides. This one may be outside the system 10 existing additional wheel spring (parallel spring) relieves when lifting and loaded when lowering. The motor vehicle can be brought in this way in the construction situation or in other level positions. As the parallel springs are loaded or unloaded, the spring elements become 60 . 62 loaded or unloaded. According to the different Federkennungen must for the spring elements 60 . 62 a spring travel be kept.

The effect of the element 70 symbolically combined means for fluid volume displacement and the on and off switchable progression elements is the following: while the means for fluid volume displacement, a shift of hydraulic fluid 23 allow and be used for a left-right height compensation, can be realized by a parallel connection of several on and off switchable progression elements with different spring and damper properties several stabilizer characteristics. For n elements, 2 ⁿ identifiers can be implemented. The transition to the "active chassis" is completed when the connection can be brought into meaningful dependence on the driving condition.

The valve control box 68 at the same time enables the functional decoupling of the two hydraulic units 12 . 14 and the short circuit of the first pressure chamber 16 . 20 with the second pressure chamber 18 . 22 with each of the two hydraulic units 12 . 14 , The stabilizer effect is omitted in this case. However, the wheel-related spring rate remains the same. Since in this switching variant, the fluid volumes are mixed in a state in which their distribution to the different pressure chambers is not necessarily the same, after switching to "base" determined by sensors characteristics have the volumes on the fluid volume displacement element 70 be compensated again.

In addition to the operation of the hydraulic system 10 already mentioned displacement and pressure sensors are for the use of the hydraulic system 10 as "active chassis" other sensors for example steering angle, speed, braking pressures, yaw rate, wheel pressures, etc. for controlling / controlling the system necessary.

Further construction examples for a hydraulic unit 12 . 14 are in 3 and 4 shown. Here is in the piston unit 36 in each case the second piston 48 parallel to the third piston 52 arranged and both pistons 48 . 52 are over a common floor plate 76 rigidly connected. In addition, the second and third attack surface A ₂ , A _{3 of} the piston unit 36 and the first engagement surface A _{1 of} the first piston 32 arranged side by side. The installation of the spring element 60 is in the so-called first empty space 78 that is, the space between the case 28 and the second pressure chamber 18 opposite surface of the piston unit 36 formed space, takes place. The two in 3 and 4 shown embodiments of a hydraulic unit 12 . 14 are characterized in particular by the smaller space requirement.

Corresponding are more circuit variants possible. For example, let the second and third pistons of the hydraulic unit are placed in series and at the same time the first and second pistons of the same hydraulic unit next to each other (parallel). The same can be said of the second and third piston in parallel and at the same time the first piston in series with the second piston of the hydraulic unit.

In 5 is the use of the hydraulic system 10 shown for Bremsnickausgleich. In the 5 The elements shown on the left side here are the front axle and corresponding to the arranged on the right side elements of the rear axle assigned. At the front axle and rear axle is on each wheel depending Weil a hydraulic unit, here a cylinder front axle left 80 , a cylinder front axle right 82 , a cylinder rear axle left 84 , and a cylinder, rear right 86 arranged. The pressure chambers of the cylinders of an axle are directly coupled with each other. This means that in the pressure chambers of the cylinder 80 and 82 the same, first system pressure is present. The in the pressure chambers of the cylinders 84 . 86 the present second system pressure usually deviates from the first system pressure. About pressure lines is the first system pressure at the attack surface A _{2 of} the piston unit 36 to the first hydraulic unit. Accordingly, the second system pressure is at the attack surface A _{2 of} the piston unit 38 the second hydraulic unit. Depending on the circuit of the valve box 68 is the first system pressure with decoupled axes in addition to the attack surface A _{3 of} the piston unit 36 to the first hydraulic unit. With coupled axes, the first system pressure is at the attack surface A _{3 of} the piston unit 38 the second hydraulic unit. Accordingly, the second system pressure with decoupled axes in addition to the attack surface A _{3 of} the piston unit 38 the second hydraulic unit and coupled axes on the attack surface A _{3 of} the piston unit 36 to the first hydraulic unit. The piston units 36 . 38 are supported by the spring elements 60 . 62 opposite the housings 28 . 30 from. In the coupled state, there is an additional brake-knee compensation. In the decoupled state, the axes do not influence each other. Between left and right side of an axis, the in 5 system shown a mutual influence, which usually requires an adjustment of the axle-related stabilizer rate. In addition, the in 5 The system shown here has its own spring rate for each axle, which must be included in the axle-related spring design.

10

hydraulic spring system

12

first hydraulic unit

14

second hydraulic unit

16

first Pressure chamber of the first hydraulic unit

18

second Pressure chamber of the first hydraulic unit

20

first Pressure chamber of the second hydraulic unit

22

second Pressure chamber of the second hydraulic unit

23

hydraulic fluid

24

first pressure line

25

pressure line before the second pressure chamber of the first

hydraulic unit

26

second pressure line

27

pressure line before the second pressure chamber of the second

hydraulic unit

28

Housing of first hydraulic unit

30

Housing of second hydraulic unit

32

first Piston of the first hydraulic unit

34

first Piston of the second hydraulic unit

36

piston unit the first hydraulic unit

38

piston unit the second hydraulic unit

40

first Piston rod of the first hydraulic unit

42

first Piston rod of the second hydraulic unit

44

fastener the first hydraulic unit

46

fastener the second hydraulic unit

48

second Piston of the first hydraulic unit

50

second Piston of the second hydraulic unit

52

third Piston of the first hydraulic unit

54

third Piston of the second hydraulic unit

56

second Piston rod of the first hydraulic unit

58

second Piston rod of the second hydraulic unit

60

spring element the first hydraulic unit

62

spring element the second hydraulic unit

64

gap the first hydraulic unit

66

gap the second hydraulic unit

68

medium for shorting the pressure lines

70

medium for fluid volume shift / progression

elements

72

Storage with hydraulic fluid

74

throttle

76

floor area the piston unit

78

first empty displacement

79

second empty displacement

80

Cylinder, Front axle left

82

Cylinder, Front axle right

84

Cylinder, Rear axle left

86

Cylinder, Rear axle right

88

pressure chamber the piston of the front axle left

90

pressure chamber of the piston of the front axle on the right

92

pressure chamber the piston of the rear axle left

94

pressure chamber the piston of the rear axle right

96

cover

98

coupling piece

100

ground

102

ground (first pressure chamber)

104

second coupling piece

106

intermediate pipe

108

pollution protection

110

outer tube

112

fastening eye (below)

114

connection first pressure line

116

connection second pressure line

118

Spring pad above

120

Spring pad below

122

pressure chamber before the second piston of the hydraulic unit

Ness

A ₁

Attack surface of the first piston

A ₂

Attack surface of the second piston

A ₃

Attack surface of the third piston

F ₁

force

Claims (21)

Hydraulic spring system ( 10 ) with stabilizer function for an axle of a motor vehicle with a first and a second hydraulic unit ( 12 . 14 ), which are arranged between the motor vehicle body and a suspension element, with in the hydraulic units ( 12 . 14 ) guided piston ( 32 . 48 . 42 . 34 . 50 . 54 ) in each hydraulic unit ( 12 . 14 ) one with hydraulic fluid ( 23 ) filled first and second pressure chamber ( 16 . 18 . 20 . 22 ), whereby the hydraulic units ( 12 . 14 ) for the introduction of force in each case via a first piston rod ( 40 . 42 ) are connected to the suspension element, and the pressure chambers ( 16 . 18 . 20 . 22 ) of the two hydraulic units ( 12 . 14 ) via a first and second pressure line ( 24 . 26 ) in cross-connection with each other to allow power transmission from a suspension to the remote side, characterized in that in each hydraulic unit ( 12 . 14 ) a first piston ( 32 . 34 ) with its first attack surface (A ₁ ) over that in the first pressure chamber ( 16 . 20 ) located hydraulic fluid ( 23 ) with a second engagement surface (A ₂ ) of a second piston ( 48 . 50 ) is in operative connection, wherein the second piston ( 48 . 50 ) with a third piston ( 52 . 54 ) and a piston unit ( 36 . 38 ), and the third piston ( 52 . 54 ) with its third attack surface (A ₃ ) with that in the second pressure chamber ( 18 . 22 ) hydraulic fluid ( 23 ) is in operative connection, and that the piston unit ( 36 . 38 ) via at least one spring element ( 60 . 62 ) with respect to a spring-mounted body part housing ( 28 . 30 ) of the hydraulic units ( 12 . 14 ) is supported. Hydraulic spring system according to claim 1, characterized in that the third engagement surface (A ₃ ) of the third piston (A ₃ ) 52 . 54 ) smaller than that second attack surface (A ₂ ) of the second piston ( 48 . 50 ). Hydraulic spring system according to claim 1 or 2, characterized in that the first engagement surface (A ₁ ) of the first piston (A ₁ ) 32 . 34 ) and the second engagement surface (A ₂ ) of the second piston ( 48 . 50 ) are the same size. Hydraulic spring system according to claim 1 or 2, characterized in that the first engagement surface (A ₁ ) of the first piston (A ₁ ) 32 . 34 ) and the second engagement surface (A ₂ ) of the second piston ( 48 . 50 ) are different in size. Hydraulic spring system according to one of claims 1 to 4, characterized in that in the piston unit ( 36 . 38 ) the second and third pistons ( 48 . 50 . 52 . 54 ) are arranged in series and the two pistons ( 48 . 50 . 52 . 54 ) via a second piston rod ( 40 . 42 ) are rigidly connected. Hydraulic spring system according to one of claims 1 to 4, characterized in that in the piston unit ( 36 . 38 ) the second piston ( 48 . 50 ) parallel to the third piston ( 52 . 54 ) is arranged and the two pistons ( 48 . 50 . 52 . 54 ) over a common floor area ( 76 ) are rigidly connected. Hydraulic spring system according to one of claims 1 to 6, characterized in that the second and third engagement surface (A ₂ , A ₃ ) of the piston unit ( 36 . 38 ) and the first attack surface (A ₁ ) of the first piston (A ₁ ) 32 . 34 ) are arranged one behind the other. Hydraulic spring system according to one of claims 1 to 6, characterized in that the second and third engagement surface (A ₂ , A ₃ ) of the piston unit ( 36 . 38 ) and the first attack surface (A ₁ ) of the first piston (A ₁ ) 32 . 34 ) are arranged side by side. Hydraulic spring system according to one of the preceding claims, characterized in that the axial movability of the first piston ( 32 . 34 ) and the piston unit ( 36 . 38 ) within the hydraulic units ( 12 . 14 ) is each limited by an upper and lower stop position. Hydraulic spring system according to claim 9, characterized in that a method of the first piston ( 32 . 34 ) in its lower stop position is not also a method of the piston unit ( 36 . 38 ) in the lower stop position, and that in this position of the first piston ( 32 . 34 ) and the piston unit ( 36 . 38 ) in the housing ( 28 . 30 ) arranged spring element ( 60 . 62 ) still has a minimum pressure generating bias. Hydraulic spring system according to one of the preceding claims, characterized in that the spring element ( 60 . 62 ) in one between the housing ( 28 . 30 ) and the second pressure chamber ( 18 . 22 ) facing away from the surface of the piston unit ( 36 . 38 ) space - first Leerhubraum ( 78 ) - and / or in one between the housing ( 28 . 30 ) and the first pressure chamber ( 18 . 22 ) facing away from the surface of the piston unit ( 36 . 38 ) space - space ( 64 . 66 ) - is arranged. Hydraulic spring system according to one of the preceding claims, characterized in that in the hydraulic units ( 12 . 14 ) is arranged in each case at least one damping element. Hydraulic spring system according to claim 12, characterized in that the damping element in the first Leerhubraum ( 78 ) and / or in the intermediate space ( 64 . 66 ) and / or in one between the housing ( 28 . 30 ) and the first pressure chamber ( 16 . 20 ) facing away from the surface of the first piston ( 32 . 34 ) space - second Leerhubraum ( 79 ) - is arranged. Hydraulic spring system according to one of the preceding claims, characterized in that the pressure lines ( 24 . 26 ) each have a damping element. Hydraulic spring system according to claim 14, characterized in that as a damping element in the pressure lines ( 24 . 26 ) a throttle ( 74 ) is arranged. Hydraulic spring system according to one of the preceding claims, characterized in that the two pressure lines ( 24 . 26 ) on funds ( 68 ) are optionally short-circuited. Hydraulic spring system according to one of the preceding claims, characterized in that on the first and / or second pressure line ( 24 . 26 ) at least one memory that can be switched on and off ( 72 ) with hydraulic fluid ( 23 ) and / or at least one on and off switchable progression element and / or means for fluid displacement are arranged. Hydraulic spring system according to one of the preceding claims, characterized in that between the pressure lines ( 24 . 26 ) Medium ( 70 ) are arranged for influencing the characteristic (progression elements) and / or for fluid volume displacement, which are formed as a pump and / or actuator and / or sliding element. Hydraulic spring system according to claim 18, characterized characterized in that in the presence of at least two progression elements these are arranged in parallel. Hydraulic spring system according to one of the preceding claims, characterized in that the hydraulic spring system ( 10 ) is controllable via a plurality of sensors as a function of various influencing variables, in particular piston travel, pressure, steering angle, speed, brake pressure, yaw rate, wheel pressure or the like. Hydraulic spring system according to one of the preceding Claims, characterized in that the spring system each two axle-related cylinder for brake / pitch compensation has.