Method and device for reducing pressure pulsations in a hydraulic system

Abstract

The invention relates to a method and a device (1) for reducing pressure pulsations in a hydraulic system (2). In order to effect this reduction close to the source of the volume flow pulsation, it is proposed that a natural frequency of an oscillatory system formed from the resilient intermediate element (9) or the resilient intermediate elements (9) and from the moments of inertia of drive or output (3), displacement unit (5) and rotationally elastic coupling device (4) about the particular, in particular common, axis of rotation (A) and a pulsation frequency of the volume flow pulsation are substantially equal, and that the coupling halves (8a, 8b) are force-transmittingly interconnected, optionally using at least one rigid intermediate element (13), exclusively via the resilient intermediate element (9) or the resilient intermediate elements (9).

Description

[0001] Method and device for reducing pressure pulsations in a hydraulic system

[0002] Technical area

[0003] The invention relates to a method and a device for reducing pressure pulsations in a hydraulic system.

[0004] State of the art

[0005] Hydraulic displacement units in the form of gear, piston, or vane pumps, or corresponding motors, generate flow pulsations that lead to pressure pulsations in the connected hydraulic systems. These pressure pulsations cause vibrations in the surrounding structures, noise, and unwanted movements of the connected actuators. Devices for reducing these pressure pulsations in a hydraulic system are known from the prior art.

[0006] For this purpose, EP1384025B1 proposes the use of a vibrating body that can be actuated by the hydraulic system and supported by a spring element. The disadvantages of this design are, on the one hand, the required installation space and, on the other hand, the spatial distance from the source of the volume flow pulsation, which can be located, for example, in the pressure chamber of a piston pump.

[0007] Furthermore, it is known from the prior art to use a torsionally flexible coupling device in the drive train of a displacement unit. To this end, EP2317097A2 proposes providing a torsionally flexible coupling in the drive train between a drive motor and a hydraulic pump. This coupling device serves to reduce the transmission of torsional vibrations from the drive motor to the downstream parts of the drive train. Together with the mass moment of inertia of the drive motor, such a coupling serves to filter the excitation frequencies of the drive motor and, due to the resonance during acceleration, must contain both spring and damping elements. The disadvantage of such a coupling device is that it cannot significantly suppress any harmonic of the pressure pulsations for a given speed in the drive train.

[0008] Description of the invention

[0009] The object of the invention is therefore to design a device for reducing pressure pulsations in a hydraulic system in such a way that one or more harmonics of the pressure pulsations can be effectively suppressed at a specific speed in the drive train. Furthermore, the device should be structurally simple.

[0010] The invention solves the problem by the features of claim 1.

[0011] By ensuring that a natural frequency of a vibration system resulting from the resilient intermediate member or members and from the mass moments of inertia of the input or output, displacement unit and torsionally flexible coupling device related to the respective rotational axis and a pulsation frequency of the volume flow pulsation are substantially equal, and by ensuring that the coupling halves are connected to one another in a force-conducting manner, optionally using at least one rigid intermediate member, exclusively via the resilient intermediate member or members, a steady-state solution can be obtained for a constant speed without taking fluid friction into account in the displacement unit, in which the corresponding equal harmonic of all pressure pulsations in the hydraulic system is suppressed.The corresponding harmonic of the volume flow pulsation is then compensated by the rotational angle deflections of the displacer unit, which arise from the natural oscillations of the oscillating system. Furthermore, taking fluid friction into account, the corresponding harmonic of the pressure pulsations remains small.

[0012] For example, if the spring intermediate element consists of a single spring or several springs acting in parallel, the vibration system has a non-zero natural frequency, so that one harmonic of the pressure pulsations can be effectively suppressed for an operating speed. If the spring intermediate element consists of n springs and n-1 intermediate rigid intermediate elements, the vibration system has n non-zero natural frequencies, so that n harmonics of the pressure pulsations can be effectively suppressed for an operating speed.

[0013] Preferably, the input or output, displacement unit and torsionally flexible coupling device have a common rotation axis A, which can further simplify the design.

[0014] In addition to reducing vibrations and noise, the rotational angle deflections of the displacement unit can also improve pre-compression in the displacement chambers of the displacement unit. Other measures to improve pre-compression can thus be dispensed with according to the invention, which can, for example, increase the efficiency of the displacement unit. Furthermore, the solution according to the invention is comparatively simple in design and, by providing a space between the input or output drive and the displacement unit, avoids a spatial distance from the source of the volume flow pulsation. The volume flow pulsation is thus eliminated almost directly at its source.

[0015] Preferably, the coupling halves are connected to each other in a force-transmitting manner via several resilient intermediate links, for example, to facilitate a symmetrical design of the torsionally flexible coupling device. For example, four or six resilient intermediate links may be sufficient for this purpose. For example, the coupling halves are connected to each other in a force-transmitting manner via parallel-acting intermediate links, which can improve the mechanical load-bearing capacity of the coupling device. Furthermore, the coupling device can function as a torsion spring.

[0016] If the frequency deviation from the natural frequency to the pulsation frequency is at most 10 percent, preferably at most 5 percent, particularly preferably at most 2 percent, the harmonics of all pressure pulsations in the hydraulic system can be suppressed particularly effectively.

[0017] Preferably, the resilient intermediate member is designed as a helical spring, which can further simplify the design of the device. A helical spring enables high vibration amplitudes.

[0018] This is especially true if the helical spring, designed as a compression spring, runs in the circumferential direction of the input and / or output shaft.

[0019] Preferably, the coil spring is arranged circumferentially along the input and / or output shaft. This allows for easy replacement of individual springs.

[0020] As an alternative to the helical spring, it is conceivable that the spring-loaded intermediate member is designed as a bending beam, which can lead to a particularly compact device.

[0021] This is especially true if one end of the bending beam is clamped to one coupling half with radial alignment to the input and / or output shaft.

[0022] Symmetry in the torsionally flexible coupling device can be achieved relatively easily by, for example, arranging several bending beams next to each other in a star configuration. Such a coupling device can be arranged either outside or inside the housing of the displacement unit.

[0023] If at least one rigid intermediate member is arranged between several resilient intermediate members, this can, for example, make it possible to effectively suppress several harmonics of the pressure pulsations for an operating speed.

[0024] Preferably, the at least one intermediate member is arranged between several resilient intermediate members. This allows n non-zero natural frequencies to be generated in the vibration system, so that n harmonics of the pressure pulsations can be effectively suppressed for an operating speed.

[0025] This is particularly the case if the moment of inertia of the at least one rigid intermediate member relative to a rotation axis is in the range of 0.1 to 10 times the moment of inertia of the displacement unit relative to the rotation axis.

[0026] Simpler design conditions can be achieved if several parallel spring-loaded intermediate links are arranged before and after the rigid intermediate link. The spring-loaded intermediate links can be coil springs, for example. This arrangement is particularly suitable for force flow.

[0027] The device according to the invention can be particularly suitable for a device with a hydraulic system.

[0028] The invention also aims to create a method that can reduce pressure pulsations in a hydraulic system in a simple and reproducible manner. The invention achieves this objective by the features of claim 14.

[0029] By matching the natural frequency of the device's vibration system to the pulsation frequency of the volume flow pulsation generated by the device's displacement unit in the hydraulic system, pressure pulsations in the hydraulic system can be reduced consistently and reliably. This is also comparatively easy to implement.

[0030] Brief description of the drawings

[0031] The figures show, for example, the subject matter of the invention in more detail using three embodiments.

[0032] Fig. 1 is a schematic view of a device with a device according to the invention and with a hydraulic system,

[0033] Fig. 2a is a detailed view of Fig. 1 of a torsionally flexible coupling device according to a first embodiment,

[0034] Fig. 2b is a sectional view along BB of Fig. 2a,

[0035] Fig. 3a is a detailed view of Fig. 1 of a torsionally flexible coupling device according to a second embodiment,

[0036] Fig. 3b is a sectional view along CC of Fig. 3a and

[0037] Fig. 4 is a detailed view of Fig. 1 of a torsionally flexible coupling device according to a third embodiment.

[0038] Ways to implement the invention

[0039] According to Fig. 1, for example, a device 1 for reducing pressure pulsations in a hydraulic system 2 is shown. The device 1 has a drive 3, a torsionally flexible coupling device 4, and a displacement unit 5, which generates a volume flow pulsation in the hydraulic system 2.

[0040] For example, the displacement unit 5 connected to the hydraulic system 2 is a hydraulic pump. However, the displacement unit 5 can also be a hydraulic motor that generates a volume flow pulsation in the hydraulic system 2, which has not been shown in detail. The hydraulic pump can be, for example, a gear pump, piston pump, or vane pump.

[0041] In the hydraulic system 2, for example, a switching valve 14 and a hydraulic actuator 15, namely a hydraulic cylinder, are provided.

[0042] The torsionally flexible coupling device 4 has an input and an output shaft 6, 7, and two mutually rotatable coupling halves 8a, 8b between the input and output shafts 6, 7. Furthermore, the torsionally flexible coupling device 4 includes a resilient intermediate member 9 that connects the coupling halves 8a, 8b to one another in a force-transmitting manner.

[0043] As can also be seen in Fig. 1, the input shaft 6 is directly connected to the drive 3 and the output shaft 7 is directly connected to the displacement unit 5.

[0044] According to the invention, a natural frequency of a vibration system resulting from the resilient intermediate member 9 or the resilient intermediate members 9 and from the mass moments of inertia of the drive 3, the displacement unit 5, and the torsionally flexible coupling device 4 relative to their rotational axis A is adjusted to a pulsation frequency of the volume flow pulsation. This is done in such a way that a natural frequency and a pulsation frequency are substantially equal, in particular equal, in order to reduce pressure pulsations in the hydraulic system.

[0045] Preferably, the axis of rotation A for the drive 3, for the displacement unit 5 and for the torsionally flexible coupling device 4 is identical - as shown in Fig. 1. However, it is also conceivable that, for example, a gearbox not shown in detail is provided in the drive train. The respective axes of rotation can therefore also run parallel to one another (which can also be identical), inclined to one another, etc. If, for example, the vibration system has a single natural frequency, this is preferably adjusted to the fundamental frequency of the volume flow pulsation. If, for example, the vibration system has several natural frequencies, these are preferably adjusted to the dominant harmonics of the volume flow pulsation. In addition, the forces exerted on the input shaft 6 are transmitted to the output shaft 7 essentially undamped.This is achieved by connecting the coupling halves 8a, 8b to one another in a force-conducting manner, optionally using at least one rigid intermediate member 13, exclusively via the resilient intermediate member 9 or the resilient intermediate members 9.

[0046] Without considering fluid friction in the displacement unit, a steady-state solution results for constant speed, in which the corresponding harmonics of the pressure pulsations disappear at all points in the hydraulic system. The corresponding harmonics of the volume flow pulsations are then compensated by the rotational angle deflections of the displacement unit, which arise from the natural oscillations of the oscillating system.

[0047] Taking fluid friction into account, the corresponding harmonics of the pressure pulsations remain small.

[0048] As can also be seen in Figures 2b and 3b, the coupling halves 8a, 8b are connected to one another in a force-conducting manner via several resilient intermediate members 9.

[0049] According to Figures 2a and 2b, the resilient intermediate member 9 is designed as a helical spring 10a, 10b, 10c, 10d, namely as a compression spring. The four helical springs 10a, 10b, 10c, 10d extend in the circumferential direction of the input or output shaft 6, 7—as can be seen in Figure 2b. Furthermore, the helical springs 10a, 10b, 10c, 10d are arranged symmetrically in the torsionally flexible coupling device 4, and their longitudinal directions are perpendicular to one another. According to Figures 3a and 3b, the resilient intermediate member 9 is designed as a bending beam 11a, 11b, 11c, 11d, 11e, 11f. One end of each of the six bending beams 11 a, 11 b, 11 c, 11 d, 11 e or 11f is clamped to a coupling half 8a, 8b in radial alignment with the input or output shaft 6, 7 - which can be seen in Fig. 3b.The longitudinal directions of the bending beams converge towards a common intersection point, whereby these bending beams 11 a, 11 b, 11 c, 11 d, 11 e, 11 f are arranged next to each other in a star shape.

[0050] According to Figure 4, a rigid intermediate member 13 is arranged between several resilient intermediate members 9. The moment of inertia of the rigid intermediate member 13 relative to the rotational axis A is in the range of 0.1 to 10 times the moment of inertia of the displacement unit 5 relative to the rotational axis A. Preferably, the rotational axis A is identical for the rigid intermediate member 13, for the drive 3, for the displacement unit 5, and for the torsionally flexible coupling device 4.

[0051] The resilient intermediate members 9 before and after the rigid intermediate member 13 are formed by several parallel acting bending beams 11a to 11f and 12a to 12f respectively - as this structure is shown for the bending beams 11a to 11f in Figs. 3a and 3b.

[0052] This allows two natural frequencies different from zero to be generated in the vibration system, so that two harmonics of the pressure pulsations can be effectively suppressed for an operating speed.

[0053] In general, it is noted that "in particular" can be translated into English as "more particularly." A feature preceded by "in particular" is to be considered an optional feature that can be omitted and thus does not constitute a limitation, for example, of the claims. The same applies to "vorzugsweise," translated into English as "preferably."

Claims

P a t e n t a n s p r ü c h e:

1. Device for reducing pressure pulsations in a hydraulic system (2), with an input or output (3), with a torsionally flexible coupling device (4) which has an input and an output shaft (6, 7) and, between the input and output shafts (6, 7), two mutually rotatable coupling halves (8a, 8b) which are connected to one another in a force-transmitting manner via at least one resilient intermediate member (9), and with a displacement unit (5) which generates a volume flow pulsation in the hydraulic system (2), wherein the input shaft (6) is connected to the input or output (3) and the output shaft (7) is connected to the displacement unit (5), characterized in that a natural frequency of a mass moment of inertia of the input or output (3) resulting from the resilient intermediate member (9) or the resilient intermediate members (9) and from the mass moments of inertia of the input or output (3) related to the respective, in particular common, axis of rotation (A),displacement unit (5) and torsionally flexible coupling device (4) resulting vibration system and a pulsation frequency of the volume flow pulsation are substantially the same, and that the coupling halves (8a, 8b) are connected to one another in a force-conducting manner, optionally using at least one rigid intermediate member (13), exclusively via the resilient intermediate member (9) or the resilient intermediate members (9).

2. Device according to claim 1, characterized in that the coupling halves (8a, 8b) are connected to one another in a force-conducting manner via several, in particular four or six, resilient intermediate members (9).

3. Device according to claim 2, characterized in that the coupling halves (8a, 8b) are connected to one another in a force-conducting manner via parallel-acting intermediate members (9).

4. Device according to claim 1, 2 or 3, characterized in that the frequency deviation from the natural frequency to the pulsation frequency is at most 10 percent, preferably at most 5 percent, particularly preferably at most 2 percent.

5. Device according to one of claims 1 to 4, characterized in that the resilient intermediate member (9) is designed as a helical spring (10a, 10b, 10c, 10d), in particular as a compression spring.

6. Device according to claim 5, characterized in that the helical spring (10a, 10b, 10c, 10d) is arranged to run in the circumferential direction of the input and / or output shaft (6, 7).

7. Device according to one of claims 1 to 4, characterized in that the resilient intermediate member (9) is designed as a bending beam (11a, 11b, 11c, 11d, 11e, 11f).

8. Device according to claim 7, characterized in that one end of the bending beam (11a, 11b, 11c, 11d, 11e, 11f) is clamped to a coupling half (8a, 8b) with radial alignment to the input and / or output shaft (6, 7).

9. Device according to claim 7 or 8, characterized in that several bending beams (11a, 11b, 11c, 11d, 11e, 11f) are arranged next to one another in a star shape.

10. Device according to one of claims 1 to 9, characterized in that the at least one rigid intermediate member (13) is arranged between several resilient intermediate members (9).

11. Device according to claim 10, characterized in that the moment of inertia of the at least one rigid intermediate member (13) related to a rotation axis (A) is in the range of 0.1 times to 10 times the moment of inertia of the displacement unit (5) related to the rotation axis (A).

12. Device according to claim 10 or 11, characterized in that, in particular in the force flow, a plurality of parallel-acting resilient intermediate members (9), in particular bending beams (11a to 11f, 12a to 12f), are arranged before and after the rigid intermediate member (13).

13. Device with a hydraulic system (2) and with a device (1) according to one of claims 1 to 12.

14. Method for reducing pressure pulsations in a hydraulic system (2), with a device (1) according to one of claims 1 to 12 or with a device according to claim 13, in which a natural frequency of the oscillation system of the device is adjusted to a pulsation frequency of the volume flow pulsation generated by the displacement unit (5) of the device in the hydraulic system (2).

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