Hydraulic Drive System

Abstract

The invention relates to a hydraulic drive system, to a method for adjusting a delivery volume in a hydraulic drive system, and to the use of the hydraulic drive system for controlling a hydraulic cylinder. The hydraulic drive system according to the invention is a hydraulic drive system with a first hydraulic machine and a second hydraulic machine which are connected mechanically to one another. The first hydraulic machine and the second hydraulic machine are operated jointly by a variable-speed drive. The first hydraulic machine and the second hydraulic machine are connected hydraulically to at least one first hydraulic cylinder, comprising a first hydraulic cylinder surface and a second hydraulic cylinder surface. The first hydraulic machine and/or the second hydraulic machine have/has an adjustable delivery volume.

Claims

1. A hydraulic drive system (1) having a first hydraulic machine (2) and a second hydraulic machine (3), which are mechanically connected to one another; wherein the first hydraulic machine (2) and the second hydraulic machine (3) are operated conjointly by a variable-speed drive (4); wherein the first hydraulic machine (2) and the second hydraulic machine (3) are hydraulically connected to at least a first hydraulic cylinder (5), comprising a first hydraulic cylinder surface (5a) and a second hydraulic cylinder surface (5b); and wherein the first hydraulic machine (2) and/or the second hydraulic machine (3) have an adjustable delivery volume.

2. The hydraulic drive system (1) as claimed in claim 1, wherein a ratio of the delivery volumes of the first hydraulic machine (2) and the second hydraulic machine (3) is mechanically adjustable to a surface ratio of the first hydraulic cylinder surface (5a) and the second hydraulic cylinder surface (5b).

3. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein a delivery volume of the hydraulic drive system (1) is controlled by a determined adjustment parameter.

4. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the first hydraulic cylinder surface (5a) and the second hydraulic cylinder surface (5b) are different.

5. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the first hydraulic machine (2) and/or the second hydraulic machine (3) are/is selected from a group of pumps comprising at least a positive displacement pump, in particular an axial piston pump, radial piston pump or vane pump, gear pump, spindle pump and the like, and wherein the manually adjustable pump is a positive displacement pump, in particular an axial piston pump, radial piston pump, or vane pump.

6. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the second hydraulic machine (2) is connected to the second hydraulic cylinder surface (5b) of the hydraulic cylinder (5).

7. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the first hydraulic machine (2) is connected to the first hydraulic cylinder surface (5a) of the hydraulic cylinder (5).

8. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the first hydraulic machine (2) is connected to a reservoir (6) of the hydraulic drive system (1).

9. The hydraulic drive system (1) as claimed in the directly preceding claim, wherein the reservoir (6) is configured as a pre-stressed reservoir (6).

10. The hydraulic drive system (1) as claimed in the directly preceding claim, wherein the pre-stressed reservoir (6) has a pressure in a fluctuation range preferably of 22 bar, more preferably of 14 bar.

11. The hydraulic drive system (1) as claimed in one of the preceding claims, wherein the second hydraulic machine (3) is hydraulically connected to the first hydraulic cylinder surface (5a).

12. The hydraulic drive system (1) as claimed in one of claims 1 to 10, wherein the second hydraulic machine (2) is hydraulically connected to a reservoir of the hydraulic drive system (1).

13. The hydraulic drive system (1) as claimed in one of claims 1 to 12, wherein the first hydraulic machine (2) and/or the second hydraulic machine (3) have/has at least one high-pressure port.

14. A method (10) for adjusting a delivery volume in a hydraulic drive system (1) having a first hydraulic machine (2) and/or a second hydraulic machine (3) as claimed in one of claims 1 to 13, comprising the following method steps: determining (S1) a surface ratio between a first hydraulic cylinder surface (5a) and a second hydraulic cylinder surface (5b) of a hydraulic cylinder (5) of the hydraulic drive system (1); determining (S2) a target delivery volume of the first hydraulic machine and/or the second hydraulic machine (3); determining (S3) a first adjustment parameter of the first hydraulic machine (2) and/or the second hydraulic machine (3), and adjusting the delivery volume of the first hydraulic machine (2) and/or the second hydraulic machine (3) of the hydraulic drive system (1) using the determined first adjustment parameter.

15. The method as claimed in the directly preceding method claim, the method comprising the further step: testing (S4) the first hydraulic machine (2) and/or the second hydraulic machine (3) on a test bench and/or by way of a test run to determine whether the adjusted delivery volume corresponds to the surface ratio of the hydraulic cylinder (5).

16. The method as claimed in one of the preceding method claims, wherein the adjustment of the delivery volume is carried out by adjusting an adjustment element using the determined first adjustment parameter, and wherein the adjustment element is preferably fixed via a locking element.

17. The method as claimed in the directly preceding method claim, wherein the adjusting element comprises at least one threaded spindle as a threaded bolt or as a threaded screw.

18. The hydraulic drive system (1) as claimed in one of claims 1 to 13, for controlling a hydraulic cylinder (5) with a constant total pressure in the hydraulic drive system (1).

Description

[0098] Showing:

[0099] FIG. 1 a first embodiment of the hydraulic drive system according to the present invention;

[0100] FIG. 2 an exemplary embodiment of the hydraulic drive system according to of the present invention, and

[0101] FIG. 3 a flow chart of an embodiment of a method according to the present invention.

[0102] FIG. 1 shows a hydraulic drive system 1. The hydraulic drive system 1 comprises a first hydraulic machine 2 and a second hydraulic machine 3.

[0103] Hydraulic machine 2 and the second hydraulic machine 3 are driven jointly via a shaft by a variable-speed drive 4. According to the invention, the first hydraulic machine 2 and the second hydraulic machine are mechanically connected to each other. The mechanical connection can be made via a shaft. The first hydraulic machine 2 and the second hydraulic machine 3 are designed as fixed displacement pumps. The first Hydraulic machine 2 is hydraulically connected to a reservoir 6. An after-suction valve (not shown) can be connected between the first hydraulic machine 2 and the reservoir 6. A reservoir 6 (expansion tank) is a container that holds the hydraulic oil or the hydraulic medium of the hydraulic drive system 1. The hydraulic fluid or the hydraulic medium can be a special mineral oil. The reservoir 6 is intended to store the hydraulic fluid, but otherwise keeps it unpressurised. The reservoir is to be understood as a tank without overpressure. This allows the reservoir 6 to be filled and emptied safely. The reservoir 6 is designed as a closed container that is connected to the surrounding air via vent valves.

[0104] is. This connection is necessary so that pressure equalisation can take place.

[0105] Returning hydraulic fluid or the hydraulic medium would otherwise generate excess pressure and outflowing hydraulic fluid would generate negative pressure. The closed system ensures that no cavitation occurs and therefore the quality of the hydraulic medium (e.g. oil) is maintained or this does not age and/or ages less quickly. This means that premature replacement and/or maintenance intervals are reduced.

[0106] In a further preferred embodiment, the reservoir 6 can be pressurised. In particular, the reservoir 6 can be designed as a pressurised reservoir.

[0107] Preferably, an overpressure in a range of 2-25 bar, particularly preferably can be provided in a range of 2-10 bar. A reservoir with overpressure enables increased suction by the first hydraulic motor and the second hydraulic motor. Furthermore, this structure can separate the hydraulic medium from the atmosphere and thus counteract ageing of the hydraulic medium.

[0108] In a further preferred embodiment, the pre-tensioned reservoir 6 is pressurised to a fluctuation range of preferably 22 bar, more preferably 14 bar. In an advantageous manner, the hydraulic pumps can be operated in this fluctuation range without reducing their sealing quality and/or quality. Furthermore, the hydraulic pumps can be operated in a range in which the load limits of the pump housing are complied with in order to prevent to prevent damage.

[0109] The first hydraulic machine 2 and the second hydraulic machine 3 are hydraulically connected to a first hydraulic cylinder side 5a of a hydraulic cylinder 5. The second hydraulic machine 3 is hydraulically connected to the second hydraulic cylinder side 5b of the hydraulic cylinder 5.

[0110] hydraulically connected.

[0111] When the variable-speed drive 4 drives the first hydraulic machine 2 and the second hydraulic machine 3, then, depending on the direction of rotation of the variable-speed drive 4, the first hydraulic machine 2 delivers hydraulic fluid from the reservoir 6 into the first hydraulic cylinder side 5a of the hydraulic cylinder and the second hydraulic machine 3 delivers hydraulic fluid from the reservoir 6 into the second hydraulic cylinder side 5a of the hydraulic cylinder.

[0112] Hydraulic machine 3 delivers hydraulic fluid from the second hydraulic cylinder side 5b of hydraulic cylinder 5 into the first hydraulic cylinder side 5a of hydraulic cylinder 5. The piston of hydraulic cylinder 5 is extended. If the drive 4 drives the first hydraulic machine 2 and the second hydraulic machine 3 in the other direction, the first hydraulic machine 2 delivers hydraulic fluid from the first hydraulic cylinder side 5a of the hydraulic cylinder 5 into the first hydraulic cylinder side 5b of the hydraulic cylinder 5.

[0113] hydraulic cylinder 5 into the reservoir 6 and the second hydraulic machine 3 delivers hydraulic fluid from the first hydraulic cylinder side 5a of the hydraulic cylinder into the second hydraulic cylinder side 5b of hydraulic cylinder 5. The piston of hydraulic cylinder 5 is retracted.

[0114] The delivery volume in the hydraulic drive system 1 can be controlled via the speed of the variable-speed drive 4. The first hydraulic machine 2 must be of this arrangement merely equalise the volume ratio of the first hydraulic cylinder side 5a and the second hydraulic cylinder side 5b. The delivery volume of the first hydraulic machine 2 can therefore be smaller than in other arrangements. The design of the first hydraulic machine 2 can therefore be smaller.

[0115] It is envisaged that the delivery volume of at least one hydraulic machine 2, 3 per pump revolution or to adjust and fix it mechanically. For this purpose, the fixed delivery volume of the first hydraulic motor 2 and/or the second hydraulic motor 3 is changed. In the case of a radial piston pump (RKP), for example, the delivery volume can be adjusted via the eccentricity of the stroke ring. This leads to an adjustment of the stroke of the pistons or vanes and therefore to a

[0116] Change in delivery volume per pump revolution. Via a corresponding

[0117] The eccentricity of the lifting ring can be adjusted using the spindle provided and the delivery volume per pump revolution can be adjusted and fixed. The stroke adjustment can be locked using a mechanical locking device. In the case of stroke adjustment via an adjusting spindle, the locking can be done via a lock nut. In

[0118] advantageously, the inventive structure and the use of exclusively fixed displacement pumps (for example external gear pumps, internal gear pumps, screw pumps) or variable displacement pumps (for example axial piston pumps, radial piston pumps, vane pumps) for the first hydraulic machine 2 and the second hydraulic machine 3 is essentially simpler.

[0119] and more reliable in operation compared to variable displacement pumps, whose delivery volume can be permanently adjusted during operation. The disadvantage of variable displacement pumps is that a considerable amount of additional work is required for the control system. With variable displacement pumps, the adjustment is realised via so-called control pistons, which are actuated with a corresponding pressure or a hydraulic fluid, which requires an additional proportional valve in order to regulates the pressure in the spool. A travel measuring system is also provided to record the position. Furthermore, a control system is required to supply the proportional valve. This represents a considerable additional expense. In this respect, the present invention is easier to realise in its design and is also more reliable due to the smaller number of components to be supplied.

[0120] Furthermore, it is advantageous that the control of the hydraulic drive system more efficient and simple, as the delivery volume only needs to be set or adjusted once. The delivery volume of the second hydraulic machine 3 can be matched to the hydraulic cylinder/area ratio by adjusting the extra force of the lifting ring. The conveyed volume flow in the hydraulic drive system 1 can be adjusted via the speed of the first and second hydraulic cylinders.

[0121] Hydraulic machine 2, 3.

[0122] Preferably, at least one of the hydraulic machines 2, 3 is designed as an axial piston pump, radial piston pump or vane pump and has a manual mechanical stroke adjustment of the delivery volume. The other hydraulic machine 2, 3 can be designed as a fixed displacement pump or as an adjustable fixed displacement pump.

[0123] be trained.

[0124] In the embodiment shown in FIG. 1, the volume of the first hydraulic machine 2 can be smaller than in comparison to the first hydraulic machine 2 used in the exemplary embodiment shown in FIG. 2. This means that the first hydraulic machine 2 in FIG. 1 can be designed to be correspondingly smaller, and the volume of the first hydraulic machine 2 in FIG. 2 can be smaller.

[0125] is reflected in a more cost-effective application. The second hydraulic machine shown in FIG. 1 has two connections, both of which can be pressurised to full working pressure.

[0126] In FIG. 1, the second hydraulic machine 3 has the adjustment 7. The adjustment 7 is designed to adjust the first hydraulic machine 2 and/or the second hydraulic machine 3 for the first hydraulic machine 2 and/or the second hydraulic machine 3.

[0127] to adjust an adjustable delivery volume. In particular, the delivery volume can be mechanically adjusted via the adjustment 7. In FIGS. 1 and 2, the second hydraulic machine 3 has the adjustment 7. This is only an exemplary and not a limiting illustration. If necessary, the first hydraulic machine 2 can also have the adjustment 7. Adjustment 7 can be used, for example, to

[0128] Piston pumps and vane pumps by adjusting the adjustment 7 of the

[0129] The stroke of the pistons or vanes can be adjusted manually. This stroke adjustment leads to a change in the conveying volume per revolution. The adjustment 7 can be changed with regard to the adjustment in accordance with the determined first adjustment parameter by turning it in or out. The adjustment 7 can be locked by means of a mechanical fixing device. This mechanical fixing device can be designed as a lock nut screwed onto the adjustment 7.

[0130] FIG. 2 shows a hydraulic drive system 1 according to an exemplary embodiment. The hydraulic drive system 1 according to FIG. 2 comprises a first hydraulic machine 2 and a second hydraulic machine 3. The first hydraulic machine 2 and the second hydraulic machine 3 are operated together, for example as shown, is driven by a variable-speed drive 4 via a shaft. The first hydraulic machine 2 is hydraulically connected to a first hydraulic cylinder side 5a of a hydraulic cylinder 5. The second hydraulic machine 3 is hydraulically connected to a second hydraulic cylinder side 5b of a hydraulic cylinder 5. The first hydraulic machine 2 and the second hydraulic machine 3 are each hydraulically connected to a reservoir 6 connected. A post-suction valve can be provided between the first hydraulic machine 2 and the reservoir 6 and between the second hydraulic machine 3 and the reservoir 6. In a further embodiment, the first hydraulic machine 2 and the second hydraulic machine 3 are jointly connected to the reservoir 6 via an after-suction valve.

[0131] If the variable-speed drive 4 drives the first hydraulic machine 2 and the second hydraulic machine 3, then, depending on the direction of rotation of the variable-speed drive 4, the first hydraulic machine 2 delivers hydraulic fluid from the reservoir 6 to the first hydraulic cylinder side 5a of the hydraulic cylinder 5 and the second hydraulic machine 3 delivers hydraulic fluid from the second hydraulic cylinder side 5a to the second hydraulic cylinder side 5a.

[0132] 5b of the hydraulic cylinder 5 into the reservoir 6. The piston is moved to an end position for example, the piston of the hydraulic cylinder 5 is extended. If the drive 4 drives the first hydraulic machine 2 and the second hydraulic machine 3 in the direction other than that described above, the first hydraulic machine 2 delivers hydraulic fluid from the first hydraulic cylinder side 5a of the hydraulic cylinder 5 into the first hydraulic cylinder side 5a.

[0133] reservoir 6 and the second hydraulic machine 3 delivers hydraulic fluid from the second Hydraulic cylinder side 5b of the hydraulic cylinder 5 into the reservoir 6. The piston of the hydraulic cylinder 5 is retracted. The delivery volume (volume) in the hydraulic drive system 1 is controlled by the adjustment parameter in accordance with the invention.

[0134] The interconnection of the first hydraulic machine 2 and the second hydraulic machine 3, as shown in FIGS. 1 and 2, results in the following when using a

[0135] This means that the first hydraulic machine 2 and the second hydraulic machine 3 have the same delivery volume and therefore at least one hydraulic machine can be designed smaller compared to the state of the art mentioned at the beginning, which leads to a smaller space requirement and lower economic expenditure. The can be adjusted by changing the speed of the primary drive.

[0136] and thus the travelling speed of the hydraulic cylinder 5 can be changed. Furthermore, the second hydraulic machine 3 can be designed as a 4-quadrant stage. The 4-quadrant stage can be designed as a 4-quadrant stage. Quadrant operation with positive torque and positive direction of rotation, with positive torque and negative direction of rotation, with negative torque and positive direction of rotation and with negative torque and negative direction of rotation.

[0137] In the exemplary embodiment shown in FIG. 2, the volume of the first hydraulic machine 2 is larger compared to the first hydraulic machine in FIG. 1. The second hydraulic machine 3 has two connections, whereby only one is pressurised with full working pressure.

[0138] In the setup shown in FIG. 2, the second connection of the second hydraulic machine 3 is preferably always in fluid connection with the reservoir 6. The

[0139] The second hydraulic motor 3 can therefore be designed with only one pressure connection. This simplifies the internal design of the second hydraulic motor 3. The first hydraulic motor 2, on the other hand, now provides the entire volume flow requirement of the first cylinder chamber and is therefore larger compared to the embodiment shown in FIG. 1.

[0140] The reservoir 6 can be designed as a tank without overpressure. The reservoir 6 can also be designed as a reservoir that is pressurised. Preferably, an overpressure is provided in a range of 2-25 bar, particularly preferably in a range of 2-25 bar. This enables improved suction of the first hydraulic motor 2 and second hydraulic motor 3 on one side and on the other.

[0141] On the other hand, such an appropriate design makes it possible to separate the hydraulic medium from the atmosphere and thus counteract the ageing of the hydraulic medium.

[0142] FIG. 3 shows a flow diagram of a process 10 for adjusting a delivery volume in a hydraulic drive system 1.

[0143] Drive system 1 has a first hydraulic machine 2 and a second hydraulic machine 3. The method shown in FIG. 3 can comprise the following method steps S1-S3. In a first step S1, an area ratio between a first hydraulic cylinder area 5a and a second hydraulic cylinder area 5b of a hydraulic cylinder 5 of the hydraulic drive system 1 is determined.

[0144] In a further

[0145] In step S2, a target delivery volume of the first hydraulic machine or the second hydraulic machine of the hydraulic drive system 1 is determined. In a further step S3, a first adjustment parameter of the first hydraulic machine 2 or the second hydraulic machine 3 is determined. Using the determined first adjustment parameter, the delivery volume of the first hydraulic machine 2 or the second hydraulic machine 3 is determined.

[0146] second hydraulic machine 3 of the hydraulic drive system 1. It can be used in a

[0147] In a further embodiment, it may be provided that further adjustment parameters are determined in order to adjust the delivery volume. In particular, it is envisaged that the delivery volume of the hydraulic drive system 1 can be adjusted by adjusting the delivery volumes of the first hydraulic machine 2 and the second hydraulic machine 3.

[0148] adjust.

[0149] Furthermore, it may be provided that the method comprises a further step. The further step comprises testing the first hydraulic machine 2 and/or the second hydraulic machine 3 on a test bench. Furthermore, the first hydraulic machine 2 and/or the second hydraulic machine 3 can be tested by means of a test run.

[0150] can be provided. Testing can be used to determine whether the adjusted delivery volume corresponds to the area ratio of the hydraulic cylinder.

[0151] Furthermore, it may be provided that the delivery volume is adjusted by setting an adjustment element, preferably a threaded spindle, threaded bolt or threaded screw with the determined first adjustment parameter.

[0152] Preferably, the adjustment element is provided via a counter element, preferably a contour nut.

LIST OF REFERENCE SYMBOLS

[0153] 1 Hydraulic drive system [0154] 2 First hydraulic machine [0155] 3 second hydraulic machine [0156] 4 Variable speed drive [0157] 5 Hydraulic cylinder [0158] 5a First hydraulic cylinder surface [0159] 5b Second hydraulic cylinder surface [0160] 6 Reservoir [0161] 7 Adjustment [0162] S1-S3 Process steps