EP1709334B1 - Pressure accumulator, especially pulsation damper - Google Patents

Abstract

A pressure accumulator, especially a pulsation damper, includes an accumulator housing (10) and a piston element (28) disposed in it. A bellows-type separative element (30) is supported on the piston part (28) with its one end (32) and with its other end (34) on the accumulator housing (10). The separative element (30) separates two working chambers (26, 40) within the accumulator housing (10) from each other, especially a gas chamber (26) from a fluid chamber (40), in a fluid-tight, especially gas-tight manner. To one working chamber (26), in addition to a defined volumetric proportion of a working gas, is filled with a fluid. In this manner, the working gas allows for a compression to a certain degree and for a dampening and smoothening of the pulsations of the fluid medium migrating to and occurring on the fluid side of the accumulator.

Description

The invention relates to a pressure accumulator, in particular pulsation damper, according to the feature configuration of the preamble of claim 1.

In the prior art ( WO 01/55602 A1 ) are known so-called hydropneumatic pressure accumulator, with a within the storage housing a gas space of an oil space separating bellows, in particular in the form of a metal bellows, which is attached at its one end to the storage housing so that the oil space adjacent to the inside of the bellows, at its free other end is closed by a corresponding volume changes of gas space and oil space as the two working spaces of the memory movable closure body, and with a flow of Hydraulikfluidum from and into the oil chamber releasing or blocking valve, which in a movement of the closure body, the one corresponds to predetermined maximum value increasing the volume of the gas space through which the closure body can be transferred to its blocking position, wherein the closure body is in the form of a trough, the bottom of which is designed as a movable valve member of the hydraulic fluid flow controlling valve.

As is known, care must be taken when bellows with rubber bellows or metal bellows that overloading of the bellows are avoided. In another known accumulator ( WO 97/46823 A1 ) is arranged with respect to this problem, a valve stem of the valve connected to the oil chamber relative to the closure body of the metal bellows in such a position relationship that formed as a flat end plate closure body of the metal bellows acts upon the valve stem upon reaching a desired end position and moves into the blocking position of the valve, so that the outflow of Hydraulikfluidum is prevented from the oil chamber upon reaching this end position of the end plate of the metal bellows. When the valve is closed, therefore, even if the connected hydraulic system should be depressurized, a pressure is maintained in the oil space of the accumulator which corresponds to the gas pressure currently prevailing in the grass space, so that pressure equilibrium prevails on both sides on the metal bellows.

Although thereby overloading of the bellows is prevented when the pressure of the oil side connected hydraulic system drops during operation of the accumulator, however, there is still the risk of damaging the bellows in conditions prevailing on the oil side overpressure or a lack of Vorfülldruckes on the gas side , Since in the known pressure accumulator of the type mentioned the maximum value of the volume of the gas space substantially corresponds to the stroke volume, which by the movement of the end plate taking place when the metal bellows are pulled together and pulled out, the stroke length which the end plate can cover within the storage housing must be chosen to be sufficiently long if a volume of the gas space sufficient for the operation of the storage is to be made available. In the absence of gas pre-charge or on the oil side prevailing overpressure therefore the prevailing pressure gradient acts on the fully extended and thus mechanically most heavily loaded metal bellows. It is therefore necessary to use either thicker or multilayer metal bellows. Disadvantageously, the spring stiffness is thereby greatly increased, resulting in a relatively poor response in operation. Multi-layered bellows result in increased weight and higher costs. In addition, there is a lower stroke per Belgwindung.

In the solution mentioned after the WO 01/55602 A1 In addition, a valve tappet fastened to the bottom of the trough is provided, which extends concentrically with the longitudinal axis from the storage housing and is connected to a second movable valve member, which at a predetermined minimum value of the volume of the gas space excess movement of the trough with a flow of Hydraulikfluidum in the oil space locking, second valve seat cooperates, so that there is the advantageous possibility to control the smallest value of the volume of the gas space corresponding end position of the trough with the aid of an oil-side valve. Since the entire interior of the trough is available as part of the gas space in the known solution, one achieves an optimal ratio between the overall size of the storage housing and volume of the gas space, although the volume attributable to the gas space within the storage housing for receiving and mastering, in particular in shape the pulsation damping for the hydraulic fluid as then further fluid can not be available. Although in the known solution, the storage housing can be shaped so that it forms a mechanical stop after a short stroke movement of the trough, because the entire interior of the trough is available as a gas volume space, and so far the metal bellows is protected as a whole not only against overstretching but, since it surrounds the outside of said trough, the bellows is also mechanically supported on the outside of the trough over the entire length in the gas space prevailing overpressure. Despite this fact and despite the existing very small "dead volume" between the trough and bellows is not to be ruled out in this respect, however, that individual wrinkles of the metal bellows are exposed to excessive stress and so can tear and fail. Furthermore, both in the region of the valve member and in the region of the possible abutment point between längsverfahrbarem trough and an inner wall of the storage housing seals are necessary, which are generally subject to wear and therefore can lead to failure of the known hydropneumatic accumulator solution.

To counter these disadvantages is in the DE-A-199 08 089 already proposed a generic accumulator solution. The known solution relates in particular to a pulsation damper with a storage housing and a piston part arranged therein, wherein a bellows-type separating member is supported with its one end on the piston part and with its other end on the storage housing, wherein the separating member two working spaces, in particular a gas space, from a fluid space within the storage enclosure fluid-tight, in particular gas-tight, separated from each other, and wherein the one working space is filled in addition to a predetermined volume fraction of a working gas with a fluid. The extent enclosed in the pressure chamber, the bias pressure generating pressure medium preferably consists of nitrogen gas, which is provided in the known solution as a fluid with an oil reservoir with a predetermined volume fraction. By introducing the fluid in the form of said oil reservoir on the side of the memory with the working gas, the thus formed gas space with the pressure medium in the form of nitrogen gas is reduced in volume by the fluid filling and a decoupling of working gas to fluid is such that Fluid as a damping support medium between the folds and deflections of the bellows-type separating member on the inside occurs, so that in the Aufzieh- and upsetting operations of the bellows during operation of the accumulator, the folded wall parts of the bellows so folded can be supported on the fluid as a counter-layer, resulting in a demonstrable increase in the life of the known pressure accumulator and thus leads to an increase in its reliability. However, it has been shown that, in particular with rapid pulsations and rapid pressure surges, especially at low temperatures, the known memory, based on the preservation of a long life, leaves nothing to be desired.

Based on the cited prior art, the present invention seeks to further improve the known accumulator solutions while maintaining their advantages that in a very small space a high degree of damping with respect to the pulsations of Hydraulikfluidum including fuel, such as diesel fuel further fluid is achieved in the fluid space of the pressure accumulator, with simultaneous realization of an effective protection for each fold or deflection of the bellows, in order to ensure the functionally reliable operation over a very long cycle times with a variety of changing load cycles. This object is achieved by a pressure accumulator with the features of claim 1 in its entirety.

Characterized in that, according to the characterizing part of claim 1, the fluid with which a working space is filled with the working gas is an alcohol, a fluid is used, which can flow as a highly fluid medium very quickly within the working space with the working gas and in particular the alcohol is suitable, in the range of design temperature for the accumulator, for example, from -10 ° C to + 160 ° C to fulfill its intended task. Furthermore, it is ensured by the fluid filling with the alcohol that little working gas within the fluid gets into solution, so that the effective volume fraction of working gas for the pressure shock absorption is not unnecessarily reduced. Depending on the respectively assumed position of the piston part and the extent connected bellows-like partition member, the alcohol can be displaced into the working space with the other working gas and also retrieved from there back into the spaces between the folds for Abstützvorgänge.

A combination of nitrogen gas as the working gas and ethylene alcohol as the fluid on the gas side of the reservoir has proved to be particularly advantageous as a fluid filling. Preferably, the volume proportions of working gas and fluid are chosen to be the same or, preferably, slightly more fluid than working gas is present in said working space of the pressure accumulator. In other types of embodiments, it is also possible to choose the rooms and / or the capacity of their size different. Advantageously, but then make sure that, shortly before the maximum spring travel is reached, the gas space is filled with fluid substantially.

Fluid fillable cavity can be provided so that on the fluid side of the memory the capacity for Hydraulikfluidum including fuels is increased, so as to improve the efficiency of the pressure accumulator for the pulsation damping, taking such a different way than in the previously known solutions in which an attempt has been made to improve the working capacity of the store to the effect that you put the provided cavity of the piston part on the side of the working space with the working gas (see. WO 01/55602 A1 ). It is surprising for a person of ordinary skill in the art of pressure accumulators that he by reversing this effect principle with reduced gas content with simultaneous filling With a fluid on the gas side of the accumulator to improved damping values for the fluid entering the memory comes, while achieving increased reliability. Since the pertinent storage solution for the movable parts requires no additional seals, a prerequisite for a wear-free, permanent operation is also given in this respect.

Further advantageous embodiments of the pressure accumulator according to the invention are the subject of the other dependent claims.

The invention with reference to an embodiment shown in the drawing, in which a metal bellows is used, explained in detail.

The single FIGURE shows a longitudinal section of said embodiment of the pressure accumulator.

The illustrated embodiment of a pressure accumulator is provided in particular for use in fuel and heavy oil systems, in order to dampen and smooth pressure surges of the pertinent operating medium. In the field of fuels is intended in particular to diesel fuel or the like. Furthermore, a pertinent accumulator could also be used in electro-hydraulic brake systems, for example in vehicle use. The accumulator shown has a designated as a whole with 10 storage enclosure, with a substantially circular cylindrical, pot-shaped body 12. The main part 12 has seen in the direction of the figure above a lid part 14, which connects via a screw 16 with the cup-shaped body 12 is, and a sealant in the form of a sealing ring 18 is the interior the storage enclosure 10 sealingly sealed off from the environment. For reasons of weight saving, the cover member 14 may be provided with a material recess 20, and along the longitudinal axis 22 of the memory, the lid member 14 is penetrated by a closure screw 24, after its removal via a suitable device (not shown) working gas, for example in the form of Nitrogen gas and / or a fluid, for example in the form of ethylene glycol in the one working chamber 26 of the pressure accumulator bring, which is usually referred to in the conventional storage only as a gas space.

An existing within the storage housing 10 piston member 28 is disposed axially longitudinally displaceable along the longitudinal axis 22 of the memory. Further, a bellows-like partition member 30 extends along the outer peripheral side of the piston member 28 and is supported at one end 32 on the piston member 28 and with its other end 34 on a downwardly projecting, annular extension 36 of the cover member 14 from. The separating member 30 is preferably formed in the manner of a metal bellows, with a plurality of annular individual folds 38 or deflections, which engage over the cylindrical piston part 28 on the outer circumference side in a zigzag-shaped manner in the manner of a pleating with a predeterminable distance. Furthermore, the piston part 28 separates the also referred to as the gas chamber a working space 26 of a further second working space 40 from a fluid-tight, which is referred to as a fluid chamber at this pressure accumulators.

The annular extension 36 of the cover part 14, which is to be regarded in this respect as part of the storage housing 10, has on its inside a cylindrical guide surface 42 within which the upper end of the piston member 28 longitudinally movable while maintaining a radial distance in the kind of an annular gap 44 is guided. Furthermore, the storage housing 10 seen in the direction of the figure on its underside a cylindrical connecting piece 46, with two fluid ports 48, 50 which open into a common antechamber 52 within the connecting piece 46. In this case, the two fluid ports 48, 50 at a right angle to the longitudinal axis 22 of the pressure accumulator in the connecting piece 46 in and out of this and it has proven to be favorable in terms of optimized flow guidance, if by perpendicular thereto extending deflection points 54 perpendicular to the respective orientation of the fluid port 48, 50, the fluid guide is made in such a way. For the function of the memory, it is sufficient if fluid is present in the further working space 40 via the antechamber 52, and a fluid flow is not absolutely necessary and even with a stationary fluid column occurring pulsations and pressure surges can be smoothed or attenuated accordingly. Furthermore, it is advantageous if at the same height, the fluid ports 48, 50 in the connecting piece 46 on and exit and open the same distance, due to the same-acting deflection 54, together in the vestibule 52.

To increase the volume of the fluid space on the side of the further working chamber 40 of the pressure accumulator, the piston part 28 has a cylindrical cavity 56 which essentially fills it up to a reduced wall thickness for the piston part 28. In the region of the connection between bellows-type separating member 30 with the piston member 28 at its one end 32, the piston member 28 an annular widening stop 58, for abutment with the associated, adjacent inner wall 60 of the storage housing 10, in which the antechamber 52 of the connecting piece 46 opens , The piston member 28 is further at its end opposite the stop 58 with a stop surface 62nd extending transversely to the longitudinal axis 22 of the memory extending, which serves to abut against a further opposite inner wall 64 of the storage housing 10, preferably formed by the cover part 14. With the stop surfaces thus formed a kind of overload protection is ensured, which helps prevent the metal bellows damaging upsetting or overshooting by pulling apart.

About the already shown annular gap 44, it is possible that the partial fluid filling occurs in the working space 26 between the cavities formed between the individual wrinkles 38 and the outer periphery of the piston member 28 so as to support them in the movements of the individual wrinkles 38, wherein in a compression process, in which two adjacent walls of a single fold 38 to move towards each other, that such absorbed fluid is forced back in the direction of the working space 26, which is the case, for example, when viewed in the direction of the figure of the pertinent initial state of the piston member 28 this upward in direction the inner wall 64 moves, and in an opposite movement of the piston member 28 and pulling the folds 38 corresponding fluid volume from the working space 46 via the annular gap 44 in the spaces between the folds 38 flow, as far as the pertinent gaps with the annular gap 44th and in fluid communication with the working space 26.

In essence, the pertinent working space 26 is filled with a working gas, for example nitrogen gas, which absorbs the pressure surges in the sense of smoothing or damping, which are introduced into the latter on the fluid side 40 of the reservoir. Any heating occurring in the region of the metal bellows as a bellows-type separating member 30 can likewise be achieved well with the fluid introduced into the working space 26, in particular dominate in the form of ethylene glycol, which in the rest as a low-viscosity medium has a good inflow and outflow behavior and further dissolves little working gas, which is necessary for the damping behavior of the memory. Likewise, an insert for a rubber bellows is intended as a bellows-type separating member 30.

Claims (10)

1. Pressure store, in particular a pulsation damper with a store housing (10) and a piston (28) located within the same, whereby a bellows-like separating member (30) is supported with its one end (32) on the piston (28), and with its other end (34) on the store housing (10), whereby the separating member (30) separates two working chambers (26, 40), in particular a gas chamber (26) from a fluid chamber (40), within the store housing (10) in a fluid tight way, and particular in a gas tight way, from each other, and whereby one working chamber (26) is filled with a fluid in addition to a pre-determinable volume proportion of a working gas, characterised in that the fluid with which the working chamber (26) containing the working gas is filled, is an alcohol.
2. Pressure store according to Claim 1, characterised in that the alcohol is ethylene glycol.
3. Pressure store according to Claim 2, characterised in that the other working chamber (40) is equipped with fluid connections (48, 50), via which a further fluid, in particular in the form of Diesel fuel or crude oil, can be displaced back into the interior of the store housing (10).
4. Pressure store according to Claim 3, characterised in that the piston (28) comprises a hollow space (56) on its side facing the other working chamber (40), which is envisaged for receiving the additional fluid.
5. Pressure store according to one of the Claims 1 to 4, characterised in that the piston (28) is moveably held across at least a part of its possible displacement path by means of sections (42) of the store housing (10), preferably in the cover (14) of the same, at a pre-determinable radial distance.
6. Pressure store according to one of the Claims 3 to 5, characterised in that the piston (28) is equipped with a shoulder (58) for abutting against an inner wall (60) of the store housing (10) on its side facing the fluid connection (48, 50).
7. Pressure store according to Claim 6, characterised in that the piston (28) is equipped with an abutment surface (62) for abutting a further inner wall (64) of the store housing (10), preferably formed by the cover (14) of the same, at its end located opposite the shoulder (58).
8. Pressure store according to one of the Claims 1 to 7, characterised in that the bellows-like separating member (30) consists of metal bellows with a multitude of individual folds (38) positioned one above the other.
9. Pressure store according to the Claims 3 to 8, characterised in that the fluid connections (48, 50) extend within a connector (46) of the store housing (10) and open into a common pre-chamber (52) of the same within this connector (46).
10. Pressure store according to one of the Claims 5 to 9, characterised in that the piston (28) delimits an annular gap (44) forming the radial distance, at least along a part of its possible displacement path, via which the working gas with the fluid reaches the inside of the bellow-like separating member (30).

Images