Hydraulic Accumulator

Abstract

The invention relates to a hydraulic accumulator, in particular a hydraulic accumulator in the form of a piston accumulator, having a separation element 10 arranged in an accumulator housing 14, which fluid-tightly separates two fluid chambers 16, 18 from one another, in particular a closed accumulator chamber 20 with a working gas, from a liquid chamber 22 with a working fluid, such as a hydraulic oil, and a fluid connection 24 is fluidly connected to one of the two fluid chambers. The hydraulic accumulator is characterized in that the fluid connection 24 has a magnetic field generating device 42 received in a fixed position therein, which separates magnetizable particles from the fluid passing through the fluid connection 24 in order to purify said fluid.

Description

[Technical field]

[0001] The invention particularly relates to a hydraulic accumulator in the form of a piston accumulator having a separation element arranged in an accumulator housing, which fluid-tightly separates two fluid chambers from one another, in particular a closed accumulator chamber with a working gas, from a liquid chamber with a working fluid, such as a hydraulic oil, and a fluid connection fluidically connected to one of the two fluid chambers. [Background technology]

[0002] Hydraulic accumulators, for example (hydropneumatic) piston accumulators, are used in hydraulic systems to hold a certain volume of pressurized fluid, for example hydraulic oil, and return it to the system when required. In commonly used hydropneumatic piston accumulators, where a piston separates an oil-side fluid chamber from an accumulator chamber enclosed in an accumulator housing that holds a working gas, such as nitrogen gas, the position of the piston changes during the operation of the hydraulic accumulator, and the hydraulic accumulator takes in hydraulic oil, such that when the pressure of the hydraulic accumulator increases, during this process the other fluid or working gas in the accumulator chamber is compressed at the same time. When the pressure decreases, the compressed gas expands again, returning the stored hydraulic oil to the hydraulic circuit during this process. The resulting change in the volume of the working chamber during operation each time leads to a corresponding axial movement of the piston in the accumulator housing.

[0003] During the operation of a hydraulic device such as a working cylinder, a corresponding hydraulic accumulator is connected to the hydraulic working circuit, which generally has a filter device with a filter element for cleaning particulate contamination from the working fluid, such as hydraulic oil, which filter device can be replaced with a new element if necessary. Despite these filter devices, it cannot be excluded that contaminant particles reach the clean side of the fluid and cause damage to the accumulator and its components if they reach the hydraulic accumulator. The filter elements are also limited in terms of their flow capacity, and therefore they cannot always be used at very high volumetric flows and associated high fluid pressures. In particular, when using piston accumulators, particulate contamination can unintentionally get into the sealing system of the separating piston, which can lead to failure of the accumulator and the associated hydraulic device. Since the particulate contaminations that occur are often caused by wear of the hydraulic device, they are usually metallic in nature, and the particles that occur, especially in the case of mechanical failure, can be of such a size that the sealing device on the separating piston leaks or even breaks down together with its elastomeric material.

[0004] DE 10 2016 007 798 A1 discloses a hydraulic piston accumulator with an accumulator housing having a cylindrical tube defining a longitudinal axis, which is sealed at both ends by housing covers and guided so that a piston can move longitudinally as a separating element, which separates a fluid chamber for a compressible fluid, such as a working gas, from another fluid chamber for an incompressible fluid, such as a hydraulic oil, in the housing, and a displacement measuring device for contactlessly determining the position of the piston in the housing, which has a non-magnetic measuring tube that runs through a passage formed in the piston along the longitudinal axis from one housing cover to the other and is sealed against the inside of the housing. A position sensor is slidably guided in the tube itself and follows the movement of the piston by means of a magnetic force acting between it and the piston in the measuring tube. A permanent magnet is provided on the piston for generating a magnetic force that forces a following movement of the position sensor in the measuring tube. A permanent magnet, which moves continuously with a separate piston during operation of the accumulator, is received in the fluid chamber along with a compressible working gas.

[0005] DE 41 16 482 A1 discloses a method and a device for measuring the pressure of the working gas in a gas accumulator, which can be connected to a hydraulic actuation circuit, in which the working gas is separated from the working fluid via a separation element in the form of an elastomer accumulator bladder. When the accumulator bladder is in a defined position, the gas pressure that can be assigned to the bladder due to this position is measured by a pressure sensor arranged on the fluid side, and for this purpose the position of the disk valve of the accumulator is monitored by a monitoring device. For this purpose, the disk valve has a switching element with a permanent magnet in the fluid connection of the accumulator, the associated sensor consisting of a switch that can be actuated by a magnet or using the so-called Hall effect, as soon as depending on the actuation position of the disk valve, the switching element is guided past the associated sensor and triggers it.

[0006] A cube shaped magnet that moves continuously back and forth during operation of the accumulator is inadequate, as is a ring magnet on the gas side of the accumulator housing, to effectively counteract particulate contamination occurring on the liquid side of the accumulator. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE 102016007798 A1 [Patent Document 2] DE 4116482 A1 Summary of the Invention [Problem to be solved by the invention]

[0008] Based on this state of the art, the present invention is therefore based on the object of further improving known hydraulic accumulator solutions in such a way that failures can be excluded even in the event of metal particle contamination. [Means for solving the problem]

[0009] This object is achieved by a hydraulic accumulator having the features of claim 1.

[0010] According to the characterizing part of claim 1, the fluid connection is received in a fixed position in the fluid connection and has a magnetic field generating device which serves to separate magnetizable particles in order to purify the fluid passing through the fluid connection, thereby providing the opportunity to generate a sufficiently strong fixed magnetic field fixed in position in the fluid connection area of ​​the accumulator housing, so that magnetizable particles, in particular metallic particles, cannot reach the liquid side of the accumulator and therefore do not damage, in particular the separating element such as the separating piston. In particular, the particle contaminants cannot reach the sealing side of the separating piston with the sealing ring and guide band of the hydro-pneumatic piston accumulator, otherwise the particle contaminants may lead to the separating piston being "caught" inside the accumulator housing due to friction as well as sealing problems, so that the separating piston can no longer move and the hydro-pneumatic accumulator becomes totally unusable. In particular, when the filter device controls the fluid flow reaching its limit, a reliable cleaning of the metallic magnetizable particle part from the fluid flow is achieved by the magnetic separation of the hydro-pneumatic accumulator.

[0011] In a preferred embodiment of the hydraulic accumulator according to the invention, it is provided that the magnetic field generating device consists of a permanent magnet, which is installed in the housing cover of the accumulator housing and at least partially surrounds or passes through the associated fluid connection. In this way, the entire fluid supply into the accumulator housing is controlled and purified of particle contamination before entering the liquid side. The fluid flow is guided through the permanent magnet or past the permanent magnet along a predetermined relatively long path, so that cleaning is performed very efficiently.

[0012] Preferably, the magnetic field generating device is mainly arranged in the part of the fluid connection adjacent to the fluid chamber in the accumulator housing to which the fluid connection leads. This configuration ensures that any particles that may accidentally pass between the separating element and the housing cover are expelled from the gap, which narrows corresponding to the direction of the magnet. Furthermore, there is still enough space in the other free areas of the fluid connection to be able to attach piping for the hydraulic circuit, especially by screwing.

[0013] In special cases, in order to increase the efficiency of the permanent magnets, it is also conceivable to replace them with magnets which can be energized, which requires an energy supply to the accumulator housing.

[0014] In a further preferred embodiment of the hydraulic accumulator according to the invention, it is provided that the magnetic field generating device comprises a ring which is received in an associated wall receptacle in the fluid connection and held in place by a fixing sleeve. By means of a closed ring guide, a very strong fixed magnetic field is generated for particle washing, alternatively it is also possible to use individual ring segments instead of a closed ring. Preferably, the fixing sleeve is designed as a threaded part with an external thread which engages in a correspondingly designed internal thread of the fluid connection and supports and fixes the ring against a contact shoulder of the fluid connection. In this way, a reliable positioning of the magnet ring in the fluid connection of the accumulator is achieved.

[0015] Preferably, in a variant embodiment, it is additionally or alternatively provided that the magnetic field generating device is formed from a rod which is part of a fixed plate with passages for the fluid guide and is inserted, in particular by screwing, into the fluid connection. In this way, the fluid flow is guided on all sides through the centrally located rod, so that also a good cleaning of the fluid from the magnetizable particles is achieved. If necessary, it is also possible to combine rings with rods in a common device.

[0016] Particularly good cleaning results were also obtained when the free end of the rod adjacent one of the multiple fluid chambers of the accumulator housing was arranged concentrically with the longitudinal axis of the accumulator housing and flush with the upper surface of the associated housing cover facing this fluid chamber.

[0017] In order to save space, preferably the fluid connections for the fluid supply and discharge pass through the centre of the housing cover and are arranged concentrically with the longitudinal axis of the accumulator housing.

[0018] Due to the use of filter elements in the hydraulic operating circuit, occurrence of magnetizable particle contamination is likely to be quite rare, therefore manual cleaning of the magnetic field generator due to excessive dirt accumulation is not absolutely necessary. However, in any case it is preferable to be able to remove the magnetic field generator from the fluid connection for the purpose of cleaning and / or replacement and, after cleaning or carrying out maintenance work, to reinsert it in the fluid connection for a new operation. For this replacement, the hydraulic accumulator must be stopped.

[0019] To ensure an energy-efficient use at full operating capacity, the hydraulic accumulator is preferably designed such that the separating element is formed from a separating piston that can move longitudinally in the accumulator housing and in one of its possible stop positions is flush with the fluid connection in contact with the housing cover and covers it without a step when the fluid chamber is completely emptied. During the operation of the separating piston, especially when the hydraulic fluid is returned from the fluid chamber in the direction of the hydraulic operating circuit, high fluid flow velocities arise, which in some cases allow the magnetic field generating device to be cleaned by this fluid flow and whose collected and released particulate contaminants can be cleaned from the fluid flow by the filter element during normal filtering operation.

[0020] In the following, the hydraulic accumulator according to the invention is explained in more detail by means of two exemplary embodiments. The figures below are shown in principle and are not to scale. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 shows the main structure of the hydraulic accumulator as a whole in the form of a longitudinal section. [Diagram 2] FIG. 2 is an enlarged view of the portion marked X in FIG. [Diagram 3] FIG. 3 shows a further embodiment of a hydraulic accumulator in the form of a longitudinal section. [Figure 4] FIG. 4 again shows an enlarged view of the cross section marked X in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The hydraulic accumulator according to the invention shown in Fig. 1 is in the form of a so-called piston accumulator and has a separating piston 12 as separating element 10 arranged in an accumulator housing 14, which separates two fluid chambers 16, 18 from one another. The upper fluid chamber 16, as viewed in the direction of Fig. 1, forms a closed accumulator chamber 20 for receiving a working gas, for example nitrogen gas. The lower fluid chamber 18 forms a fluid chamber 22 for receiving a working fluid, such as hydraulic oil. The fluid chamber 18 or the liquid chamber 22, respectively, is provided with a fluid connection 24, via which the accumulator can be connected to a hydraulic working circuit of conventional type, not shown in more detail.

[0023] The accumulator housing 14 is designed as a kind of cylinder or tube, between whose two free ends the separating piston 12 is guided so as to be freely movable along the housing longitudinal axis 30, sealed respectively by threaded housing covers 26, 28.

[0024] The upper housing cover 26 has a continuous fluid duct 32, which is sealed by a screw plug 34, as shown in FIG. 1. Via the corresponding arrangement 32, 34, the accumulator can be emptied of working gas in the chamber 16 if necessary, for example for maintenance work purposes, but can also fill the chamber 16 in the absence of working gas. The separation piston 12 itself is designed as a so-called hollow piston, with the aim of increasing the effective gas volume on the side of the fluid chamber 16. On its outer periphery, the separation piston 12 is guided along the inside 40 of the cylindrical accumulator housing 14 via at least one sealing ring 36 and at least one guide band 38. When manufacturing a practical embodiment, several of the above-mentioned sealing rings and guide bands can also be mounted in combination with one another on the outer periphery of the separation piston 12.

[0025] Previous designs of hydraulic accumulators, here in the form of piston accumulators, are general and therefore will no longer be described in detail, but only to the extent necessary for understanding the invention. Thus, according to the invention, the fluid connection 24, which is particularly evident from the view in Fig. 2, has a magnetic field generator 42 in the lower housing cover 28, which is received in a fixed position in the fluid connection 24 in order to separate magnetizable particles in order to purify the fluid passing through the fluid connection 24. In this case, the magnetic field generator 42 consists of a permanent magnet 44 in the form of a closed ring 46. The associated magnet ring 46 at least partially surrounds the fluid connection 24 and is mainly arranged in the part of the fluid connection 24 adjacent to the fluid chamber 18 or liquid chamber 22 through which the fluid connection 24 leads, as shown in Figs. 1 and 2.

[0026] As further shown in FIG. 2, the magnetic field generator 42 in the form of a magnet ring 46 is received in an associated wall receptacle 48 in the fluid connection 24 and held in place by a fixing sleeve 50. In this process, the ring 48 rests with its upper side, as viewed in the direction of FIGS. 1 and 2, on an annular projection 52 of the wall receptacle 48, which is achieved by a reduction in the diameter of the lower housing cover 28 in this area. The fixing sleeve 50 comprises a cylindrical support wall 54, on the inner circumference of which the ring 46 is guided and supported. The cylindrical support wall 54 terminates on an upper side 56 of the lower housing cover 28. Furthermore, starting from the cylindrical support wall 54, the fixing sleeve 50 comprises at its base an annular projection 58 which extends outwards and projects beyond the ring 46 from below and holds it in place. External threads 60 are provided on the outer periphery of the annular projection 58 and are adapted to thread into internal threads 62 in the lower housing cover 28, thereby defining the fluid connection 24. The locking sleeve 50 can be threaded onto or off of the housing cover 28 via corresponding threads formed by the external threads 60 and the internal threads 62.

[0027] Magnetizable particles in the fluid flow passing through the fluid connection 24 in the direction of the liquid chamber 22 are thus retained by the magnet ring 46 and deposited on the inner circumferential side of the fixed sleeve 50, in particular in the region of the cylindrical support wall 54. When the separating piston 12 moves to its lowest position with the liquid chamber 22 completely emptied, as viewed from the orientation of FIG. 1, it is ensured that no particulate contamination remains on the upper side 56 of the lower housing cover 28 and possibly also does not unintentionally get into the side of the sealing ring 36 between this sealing ring 36 and the inside 40 of the accumulator housing. This prevents magnetizable particulate contamination from acting in the sealing ring 36, which would result in leakage points between the accumulator chamber 20 with the working gas and the liquid chamber 22, which would render the hydraulic accumulator unusable, in particular if the working gas from the accumulator chamber 20 evaporates in the direction of the liquid chamber 22. In any case, the defined preload on the gas side of the accumulator is no longer provided. Furthermore, it cannot be excluded that the particles, especially if they have a corresponding particle size, cause the separation piston 12 to "catch" on the inside 40 of the accumulator housing 14, so that the separation piston 12 can no longer move longitudinally, thereby rendering the hydraulic accumulator unusable. This is avoided in any case of the magnetic field generating device 42.

[0028] In particular, in construction machinery, failure or wear of active elements such as valves, working cylinders or actuators can generate metallic wear particles that are "flushed" through the circuit to the hydraulic accumulator, which is also commonly used in braking systems of working machines such as construction or agricultural machines, and whose function is limited or completely stopped by destruction of the seal of the separating piston 12 by metal particles.

[0029] In this case, by using a magnetic element such as a ring magnet 46, the magnetizable metal particles can be extracted from the working fluid, thereby extending the service life of the components. In a closed hydraulic circuit, by "fishing out" said particles using a magnetic field generator 42 in the inlet area of ​​the hydraulic accumulator, the metal particles are prevented from leaving the hydraulic accumulator and causing damage to sensitive components such as valves, piston accumulator seals, etc., so that all components of the hydraulic circuit are protected from adverse effects. This is not comparable to the prior art.

[0030] The further embodiment according to Figures 3 and 4 will be described only where it differs significantly from the previous embodiment, in which the same reference numbers are used for the same components and the previous description applies analogously to the design according to Figures 3 and 4.

[0031] In a related embodiment, the magnetic field generating device consists of a magnetic rod 64, which forms part of a fixed plate 66 with a passage 68 and is inserted into the fluid connection 24 for fluid guidance, screwed in via a threaded section, in particular having an external thread 60 and an associated internal thread 62. The lower end of the rod 64 is inserted flush into a central recess 70 of the fixed plate 66 and is for example screwed or glued in. The free upper end 72 of the rod 64 is spherical and designed to adjacently face one of the fluid chambers 18 or liquid chambers 22. Furthermore, the rod 64 is guided in a concentric arrangement with the longitudinal axis 30 of the accumulator housing 14 and its upper side ends flush with the upper side 56 of the associated housing cover 28 facing this fluid chamber 18.

[0032] A number of passages 68 are arranged adjacent to the rods 64 of the fixed plate 66, two of which are shown in Figures 3 and 4, and can be grouped in several diametric arrangements relative to one another around the longitudinal axis 30. In each case, the fluid connections 24 are arranged concentrically with the longitudinal axis 30 of the accumulator housing 14 and pass through the center of the associated housing cover 28 for the supply and discharge of fluid to the fluid chamber 18, and in the process are arranged concentrically with the longitudinal axis 30 of the accumulator housing 14. The passages 68 each individually and collectively have a smaller free cross-section than the free cross-section of the fluid connections 24, so that the flow of fluid has the effect of restricting through the fixed plate 66 with the individual passages 68 in the form of holes.

[0033] 1 and 2, the fluid flow passes through the ring magnet 46, whereas in the embodiment according to Figures 3 and 4, a division of the fluid flow is caused via a passage 68, the thus divided fluid flow passing around the outer circumference of a centrally located magnetic rod 64. Magnetizable particles adhere externally to the cylindrical magnetic rod 64 and are thus prevented from entering the liquid chamber 22 with the separating piston 12 and its seal and guide systems 36, 38. In this respect too, a reliable retention of any possible magnetizable particles is achieved by the magnetic field generating device 42.

[0034] The separating piston 12 can be formed as a hollow piston in the direction of the gas side 16 in order to increase the volume of the gas chamber 20, but a corresponding hollow piston design is also possible in an additional or alternatively reverse arrangement on the fluid side 18, so that in high pressure conditions the piston 12 does not strike the housing cover 28 over its entire surface towards the liquid side 22. Moreover, it is also possible to design the separating piston 12 as a solid structure in the form of a cylindrical plate in order to ensure that the separating piston 12 does not strike the housing cover 26 of the gas side 16 even at high operating pressures.

[0035] All housing parts surrounding the permanent magnets 44 are preferably made from a non-magnetic material such as stainless steel, so that particles retained, in particular when the screws 52 are loosened, cannot become stuck in the respective openings or can be more easily removed when the inserts 56 are loosened.

[0036] The separation device for magnetizable particles according to the invention does not have to be limited to piston accumulator solutions but can also be used with other accumulator solutions having separation elements such as bladder accumulators, diaphragm accumulators and bellows accumulators. Furthermore, if necessary, a valve such as a disk valve typically used for bladder accumulators can also be inserted in the fluid connection 24 without compromising the effect of the magnetic field generating device 42.

Claims

1. A hydraulic accumulator, in particular in the form of a piston accumulator, having a separation element (10) arranged in an accumulator housing (14), said separation element (10) fluid-tightly separating two fluid chambers (16, 18) from one another, in particular separating a closed accumulator chamber (20) containing a working gas from a liquid chamber (22) containing a working fluid, such as hydraulic oil, in a hydraulic accumulator, a fluid connection (24) fluidly connected to one of the two fluid chambers (18), 1. A hydraulic accumulator, comprising: a fluid connection (24) having a magnetic field generator (42) received in a fixed position within the fluid connection (24), the magnetic field generator (42) separating magnetizable particles from the fluid passing through the fluid connection (24) in order to purify the fluid.

2. 2. A hydraulic accumulator according to claim 1, characterized in that the magnetic field generating device (42) consists of a permanent magnet (44) installed in a housing cover (28) of the accumulator housing (14) and at least partially surrounding or passing through the associated fluid connection (24).

3. 2. The hydraulic accumulator according to claim 1, wherein the magnetic field generating device (42) is disposed primarily in a portion of the accumulator housing (14) through which the fluid connection (24) communicates and adjacent to the fluid chamber (18).

4. 2. A hydraulic accumulator according to claim 1, characterized in that the magnetic field generating device (42) comprises a ring (46) received in an associated wall receptacle (48) in the fluid connection (24) and held in place by a fixing sleeve (50).

5. 5. The hydraulic accumulator according to claim 4, characterized in that the fixing sleeve (50) is designed as a threaded part having an external thread (60) which engages in a correspondingly designed internal thread (62) in the fluid connection (24), the fixing sleeve (50) supporting and fixing the ring (46) against a contact shoulder (52) of the fluid connection (24).

6. 2. A hydraulic accumulator according to claim 1, characterized in that the magnetic field generating device (42) is formed from a rod (64) which is part of a fixed plate (66) having a passage (68) for guiding a fluid and which is inserted, in particular screwed, into the fluid connection (24).

7. The magnetic field generating device (42) is formed from a rod (64), which is part of a fixed plate (66) having a passage (68) for guiding a fluid and which is inserted, in particular screwed, into the fluid connection (24); 3. A hydraulic accumulator according to claim 2, characterized in that a free end (72) of the rod (64) facing adjacent to the fluid chamber (18) of the accumulator housing (14) is flush with an upper side (56) of the associated housing cover (28) facing the fluid chamber (18), in a concentric arrangement with the longitudinal axis (30) of the accumulator housing (14).

8. 3. A hydraulic accumulator according to claim 2, characterized in that the fluid connections (24) for the supply and discharge of fluid pass through the center of the housing cover (28) and are arranged concentrically with the longitudinal axis (30) of the accumulator housing (14).

9. 2. A hydraulic accumulator according to claim 1, characterized in that the magnetic field generating device (42) can be removed from the fluid connection (24) and reinserted for cleaning and / or replacement purposes.

10. 3. The hydraulic accumulator according to claim 2, characterized in that the separating element (10) is formed by a separating piston (12) longitudinally movable inside the accumulator housing (14), which separating piston, in one of its possible rest positions, is flush with the fluid connection (24) which contacts the housing cover (28) and covers the housing cover without a step when the fluid chamber (18) is completely emptied.

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