Piston Accumulator

Abstract

The invention relates to a piston accumulator with an accumulator housing 10 in which a separating piston 12 is guided longitudinally movably, separating two fluid chambers 14, 16, in particular the fluid chamber 14 containing a working gas from a further fluid chamber 16 containing a working fluid, such as hydraulic oil, and a damping device 18, characterized in that in addition to the damping device 18, an inlet device 20 is provided which cooperates with the damping device for damping the flow of fluid leaving the accumulator housing 10 by forming a throttle in one fluid passage 22, and which opens a further fluid passage 24 by bypassing the throttled fluid passage 22, for the inlet of fluid into the accumulator housing 10.

Description

[Technical field]

[0001] The present invention relates to a piston accumulator having an accumulator housing in which a separating piston is guided longitudinally movably, which separates two fluid chambers, in particular a fluid chamber containing a working gas from a further fluid chamber containing a working fluid, such as a hydraulic oil, and which has a damping device. [Background technology]

[0002] EP 0 286 777 A1 discloses a typical piston-cylinder unit with piston end damping, which has a damping piston protruding from the end face of the piston, which recedes into a damping chamber provided at the opposite cylinder end and can taper conically in the direction of the fluid connection to form a damping gap, and in which a flow passage is provided for initiating the return stroke movement of the piston, which flow passage leads from the fluid connection for pressure oil, bypassing the damping gap, to a pressure chamber in an accumulator housing adjacent to the main piston face of the piston, and which includes a check valve. The flow passage, which can be controlled by the check valve, extends in the piston between an inlet opening at the front end of the damping piston, designed as a hollow sleeve, and an opening in the form of a transverse channel leading from the inside to the outside of the sleeve. The check valve used in this case has a solid valve plate that can be controlled by an energy accumulator in the form of a compression spring, which controls a large opening cross section in the damping piston, which leads to leakage in the closed position and turbulence in the flow passage when the valve is open. Moreover, due to the inertial behavior of the valve plate, rapid opening and closing processes are eliminated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent Application Publication No. 0286777 [Patent Document 2] German Patent No. 10337744 Summary of the Invention [Problem to be solved by the invention]

[0004] Based on this prior art, the present invention is therefore based on the object of further improving the known solution, so that a piston accumulator is created with improved end position damping for the separated piston, as well as improved response behavior when the fluid enters and leaves the hydraulic accumulator. [Means for solving the problem]

[0005] A piston accumulator having the features of claim 1 of the present application solves this problem in its entirety.

[0006] According to the characterizing part of claim 1 of the present application, in addition to the damping device, an inlet device is provided for damping the flow of fluid out of the accumulator housing by forming a throttle along one of the fluid passages, which opens a further fluid passage by bypassing the one of the fluid passages with the throttle for the inflow of fluid into the accumulator housing, which is reliably damped up to its possible stop position on the part of the accumulator housing, and when the accumulator is filled and the working fluid flows into the further fluid chamber, in the opposite direction of the movement of the separation piston, the inlet device opens and bypasses the one of the fluid passages with the throttle, which means that when the accumulator is filled and the working fluid flows into the further fluid chamber, the inlet device opens and bypasses the one of the fluid passages with the throttle, which means that the entire piston cross section responds directly when acted upon by the fluid of a given pressure and moves the separation piston against the preload of the working gas in the other fluid chamber. In this way, a high level of dynamics is achieved for the return movement of the separation piston during the filling process of the accumulator.

[0007] During further return movement of the separation piston in the direction of the fluid chamber with the working gas, when the damping device is completely disengaged from the inflow device, via the thus additionally opened fluid cross section, further inflow of fluid into the further fluid chamber is achieved, which serves to further accelerate the filling process for the accumulator.

[0008] Therefore, with the solution according to the invention, there is not only an improvement in the damping behavior achieved during the discharge of the piston accumulator, but also an improvement in unlimited backflow during the accumulator filling process, during which the separating piston is moved against the preload of the working gas in one fluid chamber.

[0009] In a preferred embodiment of the piston accumulator according to the invention, the damping device comprises a damping piston on the separating piston and the inlet device comprises an inlet piston movably guided in a portion of the accumulator housing. Due to the low mass inertia of the damping piston and the inlet piston, the fluid flow occurring during the charging and discharging of the piston accumulator can be reliably controlled in rapid succession, as a result of which even piston accumulators which have to cope with numerous load changes at very high fluid pressures during the charging and discharging processes are improved compared to prior art solutions.

[0010] In a further preferred embodiment of the piston accumulator according to the invention, it is provided that in the damping process, the damping piston engages in a recess of the inflow piston and forms a throttle gap as a throttle in one fluid passage. In this case, the throttle gap is a cylindrical annular space with a variable volume formed by adjacent wall parts of the damping piston and the inflow piston. In this way, a constant throttle gap width is achieved over the entire engagement length of the damping piston in the inflow piston, which significantly improves the end position piston damping. Since there is no need to take into account a continuously changing gap shape with a conical part, as shown in the above-mentioned prior art, the engagement length for the damping piston can be selected to be very long within predeterminable limits due to the shape to be maintained for the piston accumulator, which, together with a constant gap dimension over the entire engagement length, significantly improves the damping of the end positions of the piston.

[0011] In a further preferred embodiment of the piston accumulator according to the invention, it is provided that the inlet piston is accommodated in the housing cover as part of the accumulator housing and is inserted into a fluid connection which establishes a fluid connection to a further fluid chamber with the working fluid via a respective fluid passage. In this way, both the damping device and the inlet device with the respective fluid passage to be controlled are accommodated in a space-saving manner in the housing cover and, due to the selected design, a corresponding arrangement can be modified in an existing piston accumulator of conventional design, thus improving the damping and inlet behavior.

[0012] In a further preferred embodiment of the invention, the inlet piston is supported axially movably in the housing cover by means of a circlip, such that in the lowered position the further fluid passage is blocked and in the raised position the further fluid passage is open. By means of the circlip fastening, both the damping device and the inlet device can be fixed to the separate piston at its free end face in a very easy-to-assemble manner and can be accommodated together in a fluid connection in the adjacent housing cover at one end position of the separate piston, whereby the fluid connection forms a fluid connection between the further fluid chamber between the separate piston and the housing cover and a conventional hydraulic circuit whose components can be connected to the fluid connection by piping.

[0013] In a further preferred embodiment of the piston accumulator according to the invention, the inlet piston is inserted into the enlarged cross section of the housing cover as a component of a further fluid passage, such that a cylindrical flow chamber is created between the cylindrical outer circumference of the inlet piston and the adjacent, opposing inner circumference of the housing cover. Preferably, the inlet piston is provided with a crowned contact surface at its end face facing away from the separation piston, which can come into contact with a conical contact surface in the housing cover to form a valve seat. Thanks to the partially crowned valve seat, an articulated bearing with clearance for the inlet piston on the separation piston is achieved, even when using circlip guides, for the purpose of tolerance compensation between the separation piston with the seal and guide band and the adjacently arranged wall or casing part of the accumulator housing, in particular with the associated housing cover. For the purpose of improving the valve seat shape, it is also possible to provide the free end face of the inlet piston facing away from the separation piston with a hexagonal design or a "spot face".

[0014] For reliable guidance of the damping piston on the inlet piston, it is preferably provided in any case that in the fully discharged state of the piston accumulator, the damping piston engages completely through the inlet piston and, preferably, in the process, engages at least partially with a conical end as an insertion aid on the inlet piston until the damping piston reaches a protrusion on the edge.

[0015] The present invention further provides a method for operating a piston accumulator as described above, comprising the steps of: The method comprises: a method step of throttling the volume flow when discharging the piston accumulator by forming a hollow cylindrical throttle gap between the damping device and the inlet device; - a method step of bypassing the throttle gap when filling the piston accumulator by opening the inlet device; As a result, the method relates to a method characterized by the method step of applying a fluid pressure across the free cross-section of the separation piston in order to move the separation piston directly in the direction of a fluid chamber containing a working gas.

[0016] In the following, the piston accumulator according to the invention is explained in more detail by means of an embodiment on the basis of the drawings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows in longitudinal section the lower part of another conventional piston accumulator, as shown by way of example in the above-mentioned EP-A-0286777. [Diagram 2] FIG. 2 is a view corresponding to FIG. 1, but in the open piston position and without representation of the piston fastening. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 shows the lower part of a piston accumulator with a hollow cylindrical wall part 8 of an accumulator housing generally designated by the reference number 10, in which a separating piston 12 is guided so as to be movable in the longitudinal direction, which separates two fluid chambers 14, 16 from one another, in particular a fluid chamber 14 with a working gas, such as nitrogen, from a further fluid chamber 16 with a working fluid, such as hydraulic oil. In addition, the separating piston 12 has a damping device 18 integrally connected thereto at its free end face. Furthermore, according to the simplified diagram of FIG. 2, an inlet device 20 is provided which cooperates with the damping device 18 for damping the flow of fluid leaving the accumulator housing 10 by forming a throttle along the fluid passage 22, which inlet device 20 opens a further fluid passage 24 for the inlet of fluid into the accumulator housing 10 by bypassing one fluid passage 22 with a throttle.

[0019] As further shown in Figures 1 and 2, the damping device 18 comprises a damping piston 26, which is preferably integrally connected to the separation piston 12 and is arranged centrally on a free lower end face 28 of the separation piston 12. Furthermore, the inlet device 20 comprises an inlet piston 30, which is movably guided in a part of the accumulator housing 10, here in the form of a housing cover 32. The aforementioned housing cover 32, as part of the accumulator housing 10, is screwed onto the bottom of the hollow cylindrical wall part 8 of the accumulator housing 10 and is sealed against the remaining part of the accumulator housing 10 by means of a ring seal (not shown in detail). The separation piston 12 itself has two annular grooves 34, 36 on its outer periphery for receiving a sealing ring and a guide band (not shown in detail).

[0020] In the damping process, the damping piston 26 moves from an upper position in the inlet piston 30 into the cylindrical recess 38 (FIG. 2) and forms a throttle gap 40 as a throttle in the first fluid passage 22 thus formed. This top-down movement towards the liquid side of the accumulator ends when the end face 28 of the separation piston 12 at least partially contacts the upper face 42 of the housing cover 32, as shown in FIG. 1. Individual stop elements 44 distributed around the circumference on the end face 28 of the separation piston 12 serve as limit stops for the end face 28. According to the illustration of FIGS. 1 and 2, between the flat end face 28 of the separation piston 12 and the upper face 42 of the housing cover 32, apart from the stop elements 44 as stops, an annular gap 46 is formed, which acts as an additional damping gap and displaces fluid from the further second fluid chamber 16 in the damping function in the direction of the throttle gap 40 formed by the adjacent wall parts of the damping piston 26 and the inlet piston 30. In the discharge position of the accumulator, the working fluid thus displaced from the fluid chamber 16 passes in the direction of a fluid connection 48, via which the accumulator can be connected to a hydraulic working circuit by conventional piping (not shown). In this respect, the accumulator is kept under reduced pressure for the discharge process on the side of the fluid connection 48, and under the pre-pressure of the working gas in the fluid chamber 14, the separation piston 12 moves to its end position shown in the figure.

[0021] The inlet piston 30 is accommodated in the receiving space 50 of the lower housing cover 32 as part of the accumulator housing 10 and, as already explained, is inserted into the fluid connection 48, thereby establishing a fluid connection to the further fluid chamber 16 with the working fluid via the respective fluid passages 22, 24 and via the third fluid passage 52, which occurs in the fluid connection 48 when, due to the return stroke movement of the separation piston 12 under fluid pressure, the damping piston 26 completely disengages from the hollow cylindrical recess 38 of the inlet piston 30 together with the upward movement of the separation piston 12 in the accumulator charging position.

[0022] Before the damping piston 26 is disengaged from the inlet piston 30, the inlet piston is first raised axially upwards via the fluid pressure in the fluid connection 48, as shown in Fig. 2, the outer circumferential side of the damping piston 26 forming a cylindrical part guide for this purpose. Thus, according to the illustration of Fig. 2, the inlet piston 30 is raised by the fluid pressure in the fluid connection 48 and opens the second fluid passage 24 so that more fluid reaches the free end face 28 of the separation piston 12, and the separation piston 12 together with the damping piston 26 is raised under the fluid pressure against the preload of the working gas in the fluid chamber 14. In this way, in any case a fluid connection 54 to the further fluid chamber 16 with the working fluid is established via the second fluid passage 24, as shown in Fig. 2.

[0023] Both the separation piston 12 and the two pistons 26, 30 as well as the fluid connection 48 in the lower housing cover 32 are arranged concentrically with one another and with the longitudinal axis 56 of the accumulator housing 10. To enable the inlet piston 30 to move from its closed position according to FIG. 1 to the open passage position according to FIG. 2 and vice versa, the inlet piston 30 is mounted in the housing cover 32 by means of an elastic circlip 58 (only shown in FIG. 1) so as to be able to move in the axial direction. For this purpose, the circlip 58 engages on its outer circumferential side in an associated internal groove in the housing cover 32 and on its inner circumferential side is pierced by a contact shoulder 60, only shown in FIG. 1, which in the raised position of the inlet piston 30 shown in FIG. 2 comes into contact with the inner circumferential side of the circlip 58 and can otherwise emerge downwards a given distance from the circlip 58, as shown in FIG. 1. In this way, in any case, the circlip 58 allows the further fluid passage 24 to be blocked in the lowered position of the inlet piston 30 (FIG. 1) and to be opened in the opposite, raised position (FIG. 2). For this function, in any case, the inlet piston 30 is inserted into the enlarged cross-section 62 of the housing cover 32 to form the fluid connection 54, such that a cylindrical flow chamber is formed between the cylindrical outer periphery of the inlet piston 30 and the adjacent opposing inner periphery of the housing cover 32 to form the fluid connection 54.

[0024] At its end face facing away from the separation piston 12, the inlet piston 30 has a crowned, in particular convex, contact surface 64 which can come into contact with a corresponding conical contact surface 68 in the housing cover 32 to form a kind of valve seat 66 (FIG. 1). This crowned design achieves a self-adjustment of the inlet piston 30 in the direction of said valve seat 66 on the housing cover 32. This also ensures a centering of the separation piston 12, provided that, together with the widening of the throttle gap 40, it enters into a corresponding hollow cylindrical recess 38 in the inlet piston 30 by the cylindrical damping piston 26.

[0025] In the fully drained state illustrated in FIG. 1, the damping piston 26 penetrates completely through its inlet piston 30 and the damping piston 26 protrudes at least partially with a conical end 70 over the edge of the inlet piston 30, whereby the end slope formed on the damping piston 26 allows unhindered engagement of the inlet piston 30 with the associated downward movement of the separation piston 12 as part of the drainage process on the hydraulic or liquid side of the piston accumulator.

[0026] When this specification refers to orientations such as "top" and "bottom," this refers to the normal mode of operation of the piston accumulator in a vertical orientation.

[0027] The piston accumulator shown in Figures 1 and 2 in any case a method step of throttling the volumetric flow rate when discharging the piston accumulator by forming a hollow-cylinder throttle gap 40 between the damping piston 26 and the inlet piston 30, and displacing fluid from the fluid chamber 16 through the throttle gap 40 in the direction of a fluid connection 48, which is kept under reduced pressure, by the associated downward movement of the separating piston 12; a method step of providing a further throttle through an annular gap 46 as a damping gap between the free end face 28 of the separating piston 12 and the adjacent opposing upper face 42 of the housing cover 32; By lifting the inlet piston 30 from its valve seat 66 from the closed position according to FIG. 1 to the open position according to FIG. 2, the further fluid connection 24 is opened, thereby achieving the method step of bypassing the above-mentioned throttling or damping gaps 40, 46 when filling the piston accumulator. Due to the resulting pressure difference, the fluid under pressure thus enters the piston fluid chamber 72 between the separation piston 12 and the housing cover 32 via the fluid connection 48, whereby the separation piston 12 is then lifted upwards as viewed in the direction of the figure, and due to the further movement against the preload of the working gas in the fluid chamber 14, the liquid volume of the liquid side of the accumulator with the fluid chamber 16 increases significantly. If, during the upward movement of the separation piston 12, the central recess 38 is opened by the damping piston 26 extending outward from the inlet piston 30, a further third fluid passage 52 is opened, so that a fluid at a predefined pressure can flow directly into the piston fluid chamber 72 via the fluid connection 48. This applies a fluid pressure to the entire piston free cross section in order to move the separation piston 12 directly in the direction of the other fluid chamber 14 with the working gas. In this way, the filling process of the accumulator takes place in the usual way, and once having completed the corresponding operating cycle, the piston accumulator is then available again for the described discharge process.

[0028] According to the illustration in Fig. 1, a damping valve, generally designated by the reference number 76, is located in the region of the internal thread 74 of the fluid connection 48 and comprises a longitudinally movable valve plate 78, into which a throttle bore 80 is introduced coaxially with the longitudinal axis 56 of the piston accumulator. Said valve plate 78 is accommodated in a valve housing 82, preferably designed as a tripod, which is screwed flush along the internal thread 74 into the associated fluid connection 48. In the position shown, there is a fluid inlet 84 between the legs of the valve housing 78, so that, when the inlet device 20 is open, fluid can flow from the hydraulic circuit via the fluid connection 48 at a defined pressure in the direction of the fluid chamber 16 via a bottom inlet 86 in the valve housing 78. Conversely, i.e. when discharging the accumulator, the valve plate 78 moves from its upper displacement position shown in Figure 1 to a lower closed position, in which position the valve plate 78 is located inside the valve housing 82 and the passage of fluid is only possible via the throttle bore 80 of the valve plate 78, so that in addition to the already described throttle means 40 and / or 46 a throttling of the fluid flow is also achieved by the damping valve 76. Further details regarding the function and construction of such damping valves are also given in DE 103 37 744 A1.

[0029] Such piston accumulators usually have a high preload, which generates large forces on the separated piston 12 and its sealing system, especially during rapid discharge below the gas preload. When the piston end position shown in Figures 1 and 2 is reached, a shock-like load acts on the separated piston 12 and the associated piston seal. This means that the seal is constantly and suddenly pressed by the gas pressure against the groove side of the annular groove 34 of the separated piston 12 facing the hydraulic oil. These dynamics in the sealing system and the associated settling effect of the seal in the annular groove 34 lead to an increase in gas losses from the piston accumulator. In addition, the impact of hard metal between the separated piston 12 and the housing cover 32 can cause acoustic disturbances and, in extreme cases, associated mechanical damage in this area.

[0030] The hydraulic end position damping according to the invention presented ensures that the separation piston 12 moves at a reduced speed to its end position shown in Figure 1. However, this also reduces the sudden load on the sealing system, effectively reducing gas losses and overall wear in the accumulator, which is not comparable to the prior art.

Claims

1. A piston accumulator comprising an accumulator housing (10) in which a separation piston (12) is guided longitudinally movably, said separation piston (12) separating two fluid chambers (14, 16), in particular said separation piston (12) separating a fluid chamber (14) containing a working gas from a further fluid chamber (16) containing a working fluid, such as hydraulic oil, said separation piston (12) comprising a damping device (18), 1. A piston accumulator comprising: a piston accumulator housing having a piston accommodating a piston for accommodating a piston in said piston housing; a piston accommodating a piston in said piston for accommodating a piston in said piston; a piston accommodating a piston in said piston for accommodating a piston in said piston;

2. 2. The piston accumulator according to claim 1, characterized in that the damping device (18) comprises a damping piston (26) on the separation piston (12) and the inlet device (20) comprises an inlet piston (30) movably guided in a portion (32) of the accumulator housing (10).

3. 3. The piston accumulator according to claim 1 or 2, characterized in that during the damping process, the damping piston (26) engages in a recess (38) of the inlet piston (30) to form a throttling gap (40) as the throttling portion of the one fluid passage (22).

4. 4. The piston accumulator according to claim 1, wherein the throttle gap (40) is a cylindrical annular space having a variable volume formed by adjacent wall portions of the damping piston (26) and the inlet piston (30).

5. 5. The piston accumulator according to claim 1, wherein the inlet piston (30) is accommodated in a housing cover (32) as part of the accumulator housing (10) and is inserted into a fluid connection (48) which establishes a fluid connection (54) to the further fluid chamber (16) comprising the working fluid via the respective fluid passages (22, 24).

6. 6. A piston accumulator according to claim 1, characterized in that the inlet piston (30) is supported in the housing cover (32) by a circlip (58) such that the further fluid passage (24) is blocked in a lowered position and the further fluid passage (24) is open in a raised position.

7. 7. The piston accumulator according to any one of claims 1 to 6, characterized in that the inlet piston (30) is inserted into the enlarged cross-sectional portion (62) of the housing cover (32) such that a cylindrical flow chamber is formed between a cylindrical outer periphery of the inlet piston (30) and an adjacent opposing inner periphery of the housing cover (32).

8. 8. The piston accumulator according to claim 1, wherein the inlet piston (30) is provided, at its end face opposite the separation piston (12), with a crowned contact surface (64) capable of coming into contact with a conical contact surface (68) in the housing cover (32) to form a valve seat (66).

9. A piston accumulator according to any one of the preceding claims, characterized in that in a fully discharged state, the damping piston (26) engages fully through the inlet piston (30), preferably protruding at least partially with a conical end (70) beyond the edge of the inlet piston (30).

10. A method for operating a piston accumulator according to any one of claims 1 to 9, comprising: The method comprises: a method step of throttling the volume flow rate when discharging the piston accumulator by forming a hollow cylindrical throttle gap (40) between the damping device (18) and the inlet device (20); - a method step of bypassing the throttle gap (40) when filling the piston accumulator by opening the inlet device (20); and consequently the method step of applying a fluid pressure across the entire free cross-section of the separation piston (12) in order to move said separation piston (12) directly in the direction of a fluid chamber (14) containing a working gas.

Images