DE102011112277A1 - Piston accumulator for hydro pneumatic shock absorber device of motor car, has bellows device defining sub chamber of inner space of cylinder and arranged within inner space, and fluid path connecting part of inner space with sub chamber - Google Patents

Abstract

The accumulator (1) has a hollow cylinder (7) whose inner space (5) is divided into a gas-tight gas chamber (11) and a working chamber (15), where the gas chamber is filled with a compressible medium (9), and the working chamber is filled with a hydraulic medium (13). A separator piston (17) is longitudinally mounted within the interior space. A bellows device (21) defines a sub-chamber (19) of the inner space, and is arranged within the inner space. The separator piston comprises a fluid path (23) that connects a part of the inner space with the sub chamber. The compressible medium is selected from air, gas and gaseous mixture. Independent claims are also included for the following: (1) a method for pneumatically storage of hydraulic energy by a piston accumulator (2) a motor car.

Description

The invention relates to a piston accumulator for storing hydraulic energy according to the preamble of claim 1, a method for storing hydraulic energy according to the preamble of claim 7 and a device and / or method according to motor vehicle.

Piston accumulator and method for storing hydraulic energy are known. These can be coupled, for example, with a hydraulic system and store there accumulating or used energy and release as needed again. It is known to carry out the storage of the hydraulic energy in the form of pneumatic energy, wherein due to a working pressure, under which the hydraulic medium is, a compressible medium, such as air, can be compressed for storing the hydraulic energy. This can be done for example by means of a separating piston, wherein the separating piston can be acted upon by a first side with the working pressure of the hydraulic medium, wherein one of the first side opposite second side is associated with the compressible medium. By means of a displacement of the separating piston, a volume of the compressible medium can be increased or decreased, whereby pneumatic energy can be stored or discharged. The DE 16 25 474 A1 relates to a hydropneumatic energy storage with an elongated container, which is connected at one end to a hydraulic system and pressure sealed at the other end by a lid, and a the inside of the container into a gas and a liquid space dividing movable wall, wherein the movable wall a foil bellows attached to one end of the container. From a registration of the same Applicant with the official file number 102011106817.5 is a hydropneumatic energy storage device with a variable volume and gas-tight demarcated first gas volume, wherein the first gas volume, a hydraulic medium is assigned pressure-transmitting or assignable, known. It is envisaged that the energy storage device also has a second volume of gas which is likewise assigned to or can be assigned to the hydraulic medium in a pressure-transmitting and volume-variable and gas-tight manner, the second volume of gas being arranged radially within the first volume of gas.

The object of the invention is to provide a compact and particularly sensitive responsive piston accumulator for storing hydraulic energy, especially in transient operating conditions particularly sensitive responsive, in particular an alternative particularly sensitive responsive piston accumulator.

The object is achieved in a piston accumulator for storing hydraulic energy, having a hollow cylinder having an interior space, a separating piston which divides the interior of the hollow cylinder into a gas-tight gas space filled with a compressible medium and a working space which can be filled with a hydraulic medium and which is mounted longitudinally displaceably within the interior space, a corrugated bellows device delimiting a partial space of the interior space is arranged within the interior space and the separating piston has a fluid path, wherein the fluid path connects a part of the interior located outside the subspace of the interior space with the subspace of the interior delimited by means of the corrugated bellows device. Advantageously, the corrugated bellows device or its delimited subspace is arranged within the interior, so that a compact construction of the piston accumulator is possible. Advantageously, the corrugated bellows device or its delimited subspace is connected by means of the fluid path to the part of the interior which is not delimited by the bellows device. Advantageously, during transient states via the fluid path, an energy transfer through an overflowing medium take place. The energy is stored by means of the bellows device. This can be done, for example, before a so-called breakaway of the separating piston. Los breakage of the separating piston can be understood that this due to static friction forces, which occurs between an inner wall of the hollow cylinder and an existing seal between the separating piston and the hollow cylinder, at relatively small pressure differences is not yet in motion, ie an amount of energy or introduced removed amount of energy can not be immediately transferred to the compressible medium. As the pressure difference increases, the separating piston begins to jerk, which is referred to as breakaway. This breakaway caused in the hydraulic medium pressure differences, which are perceived in connection with a spring damper device of a motor vehicle as uncomfortable. Advantageously, these pressure differences can be avoided or at least damped by means of an overflow via the fluid path and a corresponding energy storage in the bellows device and / or by means of the bellows device.

In a further preferred exemplary embodiment of the piston accumulator, it is provided that the bellows device is arranged inside the gas space and filled with the hydraulic medium, wherein the fluid path of the separating piston connects the working space of the inner space with the partial space of the bellows device, or that the Wellbalgvorrichtung is disposed within the working space and filled with the compressible medium, wherein the fluid path of the separating piston connects the gas space of the inner space with the subspace of the bellows device. Advantageously, in different design variants, the separating piston can either be filled with the hydraulic medium, wherein it is arranged inside the gas space or filled with the compressible medium, this being arranged within the working space of the interior of the hollow cylinder. Advantageously, on the one hand, the medium flowing over the fluid path, ie either the compressible medium or the hydraulic medium in an energy-transmitting fluidic contact with the subspace of Wellbalgvorrichtung and on the other hand is an outer surface of the bellows device with the gas space or the working space in a power-transmitting contact in combination. It is thus possible to change a volume of either the gas space or the working space by a deformation of the bellows device. This is associated with an overflow of the corresponding medium, ie the compressible medium or the hydraulic medium via the fluid path. Two different energy conversions occur, firstly a conversion into potential spring energy of the corrugated bellows device and secondly due to the reduction or enlargement of the corresponding space, ie the working space or the gas space, due to the size change of the corrugated bellows device or of the subspace delimited therefrom. An enlargement of the subspace is correspondingly accompanied by a reduction of the space within which the corrugated bellows device is arranged, ie the working space or the gas space, or vice versa. This pneumatic energy is stored or released.

In a further preferred exemplary embodiment of the piston accumulator, it is provided that the corrugated bellows device has a corrugated bellows bordering the subspace in a fluid-tight manner and a spring element resetting from a volume change of the subspace of the corrugated bellows, starting from an equilibrium position of the corrugated bellows. Advantageously, the Wellbalgvorrichtung the bellows and the spring element. The bellows serves to delimit the partial space of the interior volume variable. For this purpose, for example, this can be accordion-shaped. The spring element serves to reset a deformation of the bellows by means of restoring forces applied by the spring element in a powerless and / or depressurized state into an equilibrium position. Advantageously, starting from this equilibrium position, a volume change of the delimited subspace can take place with conversion of energy by means of the spring element. Advantageously, the spring element counteracts the change in volume while reconverting the correspondingly received energy. Advantageously, the spring element can positively influence a transmission behavior of the piston accumulator during the transient state, in particular before or in a time-tight environment of breakaway of the separating piston. Advantageously, a part of the hydraulic energy can be converted by means of the spring element, although the separating piston has not yet set in motion. Advantageously, this can be avoided as uncomfortable perceived pressure fluctuations and / or pressure peaks.

In a further preferred exemplary embodiment of the piston accumulator, the procedure is such that the fluid path has a first partial fluid path shut off by means of an elastic diaphragm and a second partial fluid path connected in parallel to the first partial fluid path. Advantageously, by means of the elastic membrane within the fluid path during the transient state, energy can also be converted, that is, absorbed or released. This can advantageously bring about a permeability of the fluid path, in particular for high frequencies. Advantageously, therefore, large amounts of energy can advantageously be transmitted via the fluid path for high frequencies, which likewise positively influences a comfort impression in conjunction with a spring damper device of a motor vehicle. Advantageously, the first partial fluid path blocked off by the elastic diaphragm can be bypassed by the second partial fluid path connected in parallel. This makes it possible that during the transient state, a certain subset of the energy is transmitted via the elastic membrane. During a steady state, the elastic membrane is in a quiescent state, with all energy stored within the compressible medium trapped in the gas space. Advantageously, such a dynamic transmission behavior of the piston accumulator, ie during the transient state, can be positively influenced. Advantageously, the elastic membrane acts as a high-pass filter and the second partial fluid path connected in parallel as a low-pass filter. Overall, this results in a bandpass transmission behavior.

In a further preferred exemplary embodiment of the piston accumulator, the second partial fluid path has a higher hydraulic resistance than the first partial fluid path without consideration of the elastic diaphragm. Advantageously, the transmission behavior can be determined by means of the hydraulic resistance of the second Teilfluidpfads. This can for example have a greater length and / or a smaller cross-section than the first partial fluid path.

In a further preferred embodiment of the piston accumulator is proceed, in that the separating piston has a recess which forms a U-shaped longitudinal section, wherein the bellows device is arranged in a reduced state within the recess. The separating piston is longitudinally movable within the interior of the hollow cylinder. He can basically strike in two end positions on a front panel or a rear wall of the piston accumulator. Advantageously, the Wellbalgvorrichtung be designed so that this is reduced in conjunction with a resulting within the compressible medium pressure in the corresponding stop position in a volume such that the Wellbalgvorrichtung finds place within the recess, so despite a maximum deflection of the separating piston from possible damage is protected. It is also possible that not only the separating piston itself, but also the bellows device abuts against the bottom plate of the piston accumulator, but deformed due to the impact of such that this in the final maximum position, in which also strikes the separating piston, protected within the recess is arranged.

The object is also in a method for the pneumatic storage of hydraulic energy by means of a piston accumulator, in particular a previously described piston accumulator, by storing a first subset of the hydraulic energy in the form of potential spring energy by means of a bellows device of the piston accumulator and storing a second subset of the hydraulic energy in the form of pneumatic Energy of one of a separating piston of the piston accumulator within the gas space of the piston accumulator volume variable and fluid-tight demarcated separated compressible medium. Advantageously, the amount of energy to be stored can be divided. This can advantageously be done depending on a state of the piston accumulator. Advantageously, the first subset of the hydraulic energy can be stored and / or transmitted by means of the bellows device, which can advantageously take place, for example, before the separating piston breaks free. This can advantageously be increased comfort for an application of the method in spring damper devices of motor vehicles.

A preferred embodiment of the method is performed by storing a third subset of the hydraulic energy during a transient state of the piston accumulator in the form of potential strain energy by means of an elastic membrane. Advantageously, the third subset of the hydraulic energy can be stored in the form of the potential expansion energy of the elastic membrane. This can advantageously take place in transient states and / or for high frequencies. Advantageously results for the high frequencies and / or transient state, a comparatively soft transmission behavior, which can advantageously improve comfort in conjunction with spring damper systems for motor vehicles at high-frequency excitations.

The object is also achieved by a motor vehicle with a previously described piston accumulator and / or set up, designed, constructed and / or equipped with software for performing a method described above. This results in the advantages described above.

Further advantages, features and details will become apparent from the following description in which - where appropriate, with reference to the drawings - at least one embodiment is described in detail. Described and / or illustrated features form the subject of the invention, or independently of the claims, either alone or in any meaningful combination, and in particular can additionally also be the subject of one or more separate invention (s). The same, similar and / or functionally identical parts are provided with the same reference numerals.

Show it:

1 A schematic partial longitudinal sectional view of a piston accumulator with a bellows device;

2 Another schematic partial longitudinal sectional view of a piston accumulator with a bellows device with a two-part fluid path; and

3 A schematic longitudinal sectional view of a separating piston of the in 1 shown piston accumulator in three different states A, B, C.

1 shows a piston accumulator 1 for storing hydraulic energy 3 , The piston accumulator 1 has an interior 5 on. The interior 5 is from a hollow cylinder 7 educated. The interior 5 of the hollow cylinder 7 is partly with a compressible medium 9 filled by a gas chamber 11 is enclosed in a fluid-tight manner. A compressible medium may in particular be understood as meaning an air, a gas, a gas mixture and / or the like.

Besides, the interior is 5 partly with a hydraulic medium 13 filled. The hydraulic medium 13 is inside a workroom 15 of the interior 5 , Inside the interior 5 is a separating piston 17 arranged. The separating piston 17 is longitudinally displaceable within the interior 5 arranged and separates the interior 5 in the gas space 11 and the workroom 15 on.

The gas space 11 is also still in an additional subspace 19 demarcated. This is a bellows device 21 within the gas space 11 arranged.

The separating piston 17 has a fluid path 23 on. In the embodiment according to 1 connects the fluid path 23 the workroom 15 with the means of bellows device 21 delimited subspace 19 , The subspace 19 , so the bellows device 21 and the fluid path 23 , are also with the hydraulic medium 13 filled.

The in 1 illustrated piston accumulator 1 is part of a motor vehicle only partially shown 43 , The car 43 For example, may include a spring damper device, in particular a hydropneumatic spring damper device, wherein one or more of the piston accumulator 1 for temporarily storing the hydraulic energy 3 on the motor vehicle 43 can be provided.

The separating piston 17 is by means of a seal 45 fluid-tight against a the interior 5 delimiting inner surface of the hollow cylinder 7 sealed. By means of the seal 45 can be ensured that the compressible medium 9 within the gas space 11 is enclosed in a fluid-tight manner.

The bellows device 21 is also fluid-tight to the separating piston 17 assigned. The separating piston 17 has a first printing surface 47 and one of the first pressure surface 47 opposite second pressure surface 49 on. The first printing surface 47 is with a pressure of the compressible medium 9 applied. The second printing surface 49 is at a working pressure of the hydraulic medium 13 applied. Corresponding pressure forces act on the separating piston 17 , which moves accordingly in an equilibrium position. A movement of the separating piston 17 However, also acts due to sealing forces of the seal 45 counteracted frictional force. This leads to small pressure differences or pressure force differences of the first pressure surface 47 and the second pressure surface 49 no movement of the separating piston 17 cause. Only when the pressure forces have such a high difference that the frictional forces of the seal 45 be overcome, sets the separating piston 17 moving. This phenomenon is called breakaway of the separating piston 17 designated.

Advantageously, in the event that the separating piston 17 not yet moved, but already a pressure difference between the compressible medium and the hydraulic medium 13 occurs, an overflow of the hydraulic medium 13 over the fluid path 23 respectively. This leads to a deformation of the bellows device 21 and thus either an increase in volume or a decrease in volume of the bellows device 21 delimited subspace 19 , A volume change of the bellows device 21 also results in a volume change of one outside the bellows device 21 lying part of the gas space 11 of the interior 5 ,

The bellows device 21 has an in 3 illustrated spring element 27 and a corrugated bellows 25 on. In the spring element 27 it can be a separate spring, for example, the bellows 25 spans. Alternatively and / or additionally, the bellows device 21 at least have a concentric, radially extending annular fold on the flat or conical end face. In other words, the end face of the bellows device 21 seen in cross section, have a wave profile. Furthermore, in addition, a lateral surface 25a of the bellows 25 have such a convolution or exclusively the lateral surface 25a of the bellows have this. Such Wellbälge 25 , optionally joined from individual membrane segments, are also known as membrane bellows.

Alternatively and / or additionally, the corrugated bellows 25 even have elastic properties. Advantageously, a first subset 37 the hydraulic energy 3 in the form of potential spring energy of the spring element 27 be stored. A second subset 39 can be stored in the form of pneumatic energy. In 1 By way of example, arrows are shown, wherein energy flows are symbolized, which at an inflow of the hydraulic medium 13 in the interior 5 of the piston accumulator 1 occur. The inflow of the hydraulic medium 13 done by means of a connection 51 , For example, designed as a bore of the hollow cylinder 7 , this hole of the connector 51 in the workroom 15 empties.

To an inflow and / or outflow of the hydraulic medium 13 in the workroom 15 through the hole of the connection 51 to allow are within the workspace 15 spacer 53 intended. The spacers 53 space the separating piston 17 from a floor plate 55 of the piston accumulator 1 , By means of the bottom plate 55 becomes the hollow cylinder 7 for forming the fluid-tight interior 5 sealed fluid-tight. This is between the bottom plate 55 and the inner surface of the hollow cylinder 7 another seal 57 intended.

The second subset 39 becomes on the compressible medium in two different ways 9 of the gas space 11 transfer. A first subset can by means of a displacement of the separating piston 17 inside the interior 5 on the compressible medium 9 be transmitted. This is the gas space 11 reduced or enlarged. Another subset of the second subset 39 is due to an increase in volume or volume reduction of the bellows device 21 , so of the subspace 19 the bellows device 21 on the compressible medium 9 transfer. In this case, an outside of the bellows device 21 lying part of the gas space 11 of the interior 5 changed in a volume, where also a corresponding amount of energy to the compressible medium 9 is transmitted or delivered by the latter. As the bellows device 21 with the hydraulic medium 13 is filled, so can from the hydraulic medium 13 via the bellows device 21 the energy transfer takes place.

2 shows a further piston accumulator 1 which is similar in construction to the one in 1 shown piston accumulator 1 , In the following, only the differences are discussed.

In contrast to the representation of the 1 has the separating piston 17 according to 2 a partition plate 59 and a separating plate 61 on. The partition plate 59 has second printing surface 49 on. The separating plate 61 has the first print area 47 on. The partition plate 59 and the separator plate 61 of the separating piston 17 are firmly associated with each other, for example, fixed together by means not shown screws. Another difference is between the separator plate 59 and the separation plate 61 an elastic membrane 29 arranged. The elastic membrane 29 can by means of clamping forces between the partition plate 59 and the separation plate 61 be fixed. Between the partition plate 59 , the elastic membrane 29 and the separation plate 61 This results in a fluid-tight contact contact.

Another difference points to the separating piston 17 penetrating fluid path 23 a first partial fluid path 31 and a second partial fluid path 33 on.

The first partial fluid path 31 is by means of the elastic membrane 29 sealed fluid-tight. The second partial fluid path 33 is the first partial fluid path 31 connected in parallel, so that despite the closed first Teilfluidpfad 31 via the second partial fluid path connected in parallel 33 an unhindered replacement of the hydraulic medium 13 between the workspace 15 and the subspace 19 the bellows device 21 can be done.

The second partial fluid path 33 However, it has a comparatively large hydraulic resistance, at least a greater hydraulic resistance than the first partial fluid path 31 would, if this is not the elastic membrane 29 would have.

Advantageously, thereby a transmission behavior of the fluid path 23 for different frequencies or for transient states of the piston accumulator 1 be influenced favorably. By means of the first part fluid path 31 and its elastic membrane 29 can have high frequencies under elastic deformation of the membrane 29 be transferred well. The first partial fluid path 31 acts as a high-pass filter.

A corresponding third subset 41 the hydraulic energy 3 becomes in transient states of the piston accumulator 1 , Especially in high-frequency excitations in the form of potential strain energy of the elastic membrane 29 saved and submitted.

The second partial fluid path 33 Due to its comparatively high hydraulic resistance, it has exactly the opposite transmission behavior and allows low frequencies to pass well, but is poorly continuous for high frequencies, thus exhibiting low-pass behavior. Advantageously, the fluid path acts 23 in its entirety with the first partial fluid path 31 and the second partial fluid path 33 as a bandpass filter. Advantageously, by a response of the piston accumulator 1 be favorably influenced in terms of comfort criteria and / or long-term transient response. Advantageously, high frequencies by means of the first Teilfluidpfads 31 be recorded. This can in particular in an operating state of the piston accumulator 1 take place, wherein the separating piston 17 has not broken loose. For very low frequencies also the advantageous storage by means of the bellows device 21 Being able to exploit is the second partial fluid path 33 intended. For particularly high volume flows advantageously sets a movement of the separating piston 17 one.

3 shows a detail view of in 1 shown separating piston 17 of the piston accumulator 1 in three states A, B, C.

A shows the bellows device 21 So, the corrugated bellows 25 and the cooperating with this spring element 27 in an equivalent circuit diagram representation. In illustration A of the 3 is the spring element 27 together with the bellows 25 in a state of equilibrium. This results within the bellows 25 a certain volume of the subspace 19 ,

In representation B is the volume of the subspace 19 compared to the state A reduced. Here is the corrugated bellows 25 folded up and the spring element 27 compressed by taking up potential spring energy.

In a third state C, the corrugated bellows 25 the bellows device 21 unfolded and the spring element 27 corresponding to the equilibrium state, which is shown in the state A, extended. In this state C is the subspace 19 within the bellows device 21 increases and absorbing potential spring energy the spring element 27 extended.

It can be seen that the spring element 27 Volume changes of the subspace 19 resetting counteracts. In the event that from the states B and C out any pressure forces are neutralized, the bellows device moves 21 by means of the spring element 27 automatically back to equilibrium state A. It can be seen that the state changes of the bellows device 21 always with an overflow via the fluid path 23 are connected. It does not matter if the subspace 19 the bellows device 21 with the hydraulic medium 13 is filled or in a reverse case with the compressible medium 9 , In the event that the subspace 19 with the compressible medium 9 is filled, is the bellows device 21 within the workspace 15 arranged and fluid-tight the separating piston 17 assigned.

Advantageously, therefore, the hydraulic energy 3 from the first subset 37 and from the second subset 39 and according to the embodiment of 2 additionally in the form of the third subset 41 stored and / or converted.

The second partial fluid path 33 who in 2 is shown, for example, be designed as an annular channel. This can advantageously be a length of the second Teilfluidpfads 33 be enlarged.

The corrugated bellows 25 may comprise a resilient plastic material, a metallic material and / or the like. The gas space 11 of the piston accumulator 1 is high density by means of the separating piston 17 and the bellows device 21 completed.

The piston accumulator 1 contains in a preferred design variant in the separating piston 17 Hydraulic side, the hydraulically filled, resilient bellows 25 , in particular metallic, hermetically sealed as Wellfedermetallbalg. The connecting fluid path 23 between the hydraulic side working space 15 of the separating piston 17 and the hydraulically filled elastic metal bellows or corrugated bellows 25 may consist of a longer, hydraulically to a Wellbalgfedersteifigkeit of the spring element 27 tuned annular channel of the second Teilfluidpfads 33 consist. This can be advantageous for certain resonance frequencies of a wheel suspension of the motor vehicle 43 a dynamic stiffness of the Radfederung be minimized advantageous. The annular channel of the second Teilfluidpfads 33 can as hydraulic high-frequency lots the elastic membrane 29 , in particular running as a rubber membrane, are connected in parallel.

Advantageously, results in a cost-effective, finely responsive piston accumulator 1 , Especially for an active suspension, the function of a gas storage, so the piston accumulator 1 , needed.

The construction principle of the piston accumulator 1 builds advantageous very compact and yet has a high and good response quality. In particular, a comfort behavior of the piston accumulator can be advantageous 1 be improved.

LIST OF REFERENCE NUMBERS

1

piston accumulators

3

hydraulic energy

5

inner space

7

hollow cylinder

9

compressible medium

11

headspace

13

hydraulic medium

15

working space

17

separating piston

19

subspace

21

Wellbalgvorrichtung

23

fluid path

25

bellows

25a

lateral surface

27

spring element

29

elastic membrane

31

first partial fluid path

33

second partial fluid path

35

recess

37

first subset

39

second subset

41

third subset

43

motor vehicle

45

poetry

47

first printing surface

49

second printing surface

51

connection

53

spacer

55

baseplate

57

poetry

59

separating plate

61

separator disc

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 1625474 A1 [0002]

Claims (9)

Piston accumulator ( 1 ) for storing hydraulic energy ( 3 ), with: - an interior space ( 5 ) having hollow cylinder ( 7 ), - one the interior ( 5 ) of the hollow cylinder ( 7 ) into one with a compressible medium ( 9 ) filled gas-tight gas space ( 11 ) and one with a hydraulic medium ( 13 ) fillable work space ( 15 ) and longitudinally displaceable within the interior ( 5 ) mounted separating piston ( 17 ), characterized in that inside the interior ( 5 ) a subspace ( 19 ) of the interior ( 5 ) delimiting bellows device ( 21 ) is arranged and the separating piston ( 17 ) a fluid path ( 23 ), wherein the fluid path ( 23 ) one outside the subspace ( 19 ) of the interior ( 5 ) lying part of the interior ( 5 ) with the means of bellows device ( 21 ) delimited subspace ( 19 ) of the interior ( 5 ) connects. Piston accumulator according to the preceding claim, characterized in that the bellows device ( 21 ) within the gas space ( 11 ) and with the hydraulic medium ( 13 ), the fluid path ( 23 ) of the separating piston ( 17 ) the working space ( 15 ) of the interior ( 5 ) with the subspace ( 19 ) of the bellows device ( 21 ) or that the bellows device ( 21 ) within the workspace ( 15 ) and with the compressible medium ( 9 ), the fluid path ( 23 ) of the separating piston ( 17 ) the gas space ( 11 ) of the interior ( 5 ) with the subspace ( 19 ) of the bellows device ( 21 ) connects. Piston accumulator according to the preceding claim, characterized in that the bellows device ( 21 ) one the subspace ( 19 ) fluid-tight delimiting corrugated bellows ( 25 ) and a volume change of the subspace ( 19 ) of the bellows ( 25 ) starting from an equilibrium position of the bellows ( 25 ) resetting counteracting spring element ( 27 ) having. Piston accumulator according to the preceding claim, characterized in that the fluid path ( 23 ) one by means of an elastic membrane ( 29 ) shut off the first partial fluid path ( 31 ) and a first partial fluid path ( 31 ) parallel second fluid path ( 33 ) having. Piston accumulator according to the preceding claim, characterized in that the second partial fluid path ( 33 ) has a higher hydraulic resistance than the first partial fluid path ( 31 ) without consideration of the elastic membrane ( 29 ) having. Piston accumulator according to one of the preceding claims, characterized in that the separating piston ( 17 ) a U-shaped longitudinal section forming recess ( 35 ), wherein the bellows device ( 21 ) in a reduced state within the recess ( 35 ) is arranged. Method for pneumatically storing hydraulic energy ( 3 ) by means of a piston accumulator ( 1 ), in particular a piston accumulator ( 1 ) according to one of the preceding claims, characterized by: - storing a first subset ( 37 ) of the hydraulic energy ( 3 ) in the form of potential spring energy by means of a bellows device ( 21 ) of the piston accumulator ( 1 ), - storing a second subset ( 39 ) of the hydraulic energy ( 3 ) in the form of pneumatic energy one of a separating piston ( 17 ) of the piston accumulator ( 1 ) within the gas space ( 11 ) of the piston accumulator ( 1 ) volume-variable and fluid-tight demarcated compressible medium ( 9 ). Method according to the preceding claim, characterized by: - storing a third subset ( 41 ) of the hydraulic energy ( 3 ) during a transient state of the piston accumulator ( 1 ) in the form of potential strain energy by means of an elastic membrane ( 29 ). Motor vehicle ( 43 ) with a piston accumulator according to one of the preceding claims 1-7 and / or set up, designed, constructed and / or equipped with software for carrying out a method according to one of the preceding two claims.

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