US-12618419-B2 - Hydraulic drive system

US12618419B2US 12618419 B2US12618419 B2US 12618419B2US-12618419-B2

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.

Inventors

Achim Helbig
Mattias ROEGNER
Dirk Becher
Tino Kentschke

Assignees

HMS—Hybrid Motion Solutions GmbH

Dates

Publication Date: 20260505
Application Date: 20220428
Priority Date: 20210527

Claims (12)

1 . A hydraulic drive system having a first hydraulic machine and a second hydraulic machine, which are mechanically connected to one another; wherein the first hydraulic machine and the second hydraulic machine are operated conjointly by a variable-speed drive; wherein the first hydraulic machine and the second hydraulic machine are hydraulically connected to at least a first hydraulic cylinder, comprising a first hydraulic cylinder side with a first hydraulic cylinder surface and a second hydraulic cylinder side with a second hydraulic cylinder surface; wherein the first hydraulic machine or the second hydraulic machine has an adjustable delivery volume, and wherein the first hydraulic machine and the second hydraulic machine are configured as fixed displacement pumps; wherein the first hydraulic machine is connected to a reservoir of the hydraulic drive system, and the reservoir is configured as a pre-stressed reservoir; wherein the second hydraulic machine is hydraulically connected to the first hydraulic cylinder surface and to the second hydraulic cylinder surface; and wherein, when the second hydraulic machine conveys a hydraulic fluid with a volume flow from the second hydraulic cylinder side to the first hydraulic cylinder side, then the second hydraulic machine conveys a full volume flow from the second hydraulic cylinder side to the first hydraulic cylinder side.
2 . The hydraulic drive system as claimed in claim 1 , wherein a ratio of the delivery volumes of the first hydraulic machine and the second hydraulic machine is mechanically adjustable to a surface ratio of the first hydraulic cylinder surface and the second hydraulic cylinder surface.
3 . The hydraulic drive system as claimed in claim 1 , wherein a delivery volume of the hydraulic drive system is controlled by a determined adjustment parameter.
4 . The hydraulic drive system as claimed in claim 1 , wherein the first hydraulic cylinder surface and the second hydraulic cylinder surface are different.
5 . The hydraulic drive system as claimed in claim 1 , wherein the first hydraulic machine and/or the second hydraulic machine 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, or spindle pump.
6 . The hydraulic drive system as claimed in claim 1 , wherein the first hydraulic machine is connected to the first hydraulic cylinder surface of the hydraulic cylinder.
7 . The hydraulic drive system as claimed in claim 1 , wherein the pre-stressed reservoir has a pressure in a fluctuation range preferably of 22 bar, more preferably of 14 bar.
8 . The hydraulic drive system as claimed in claim 1 , wherein the first hydraulic machine and/or the second hydraulic machine have/has at least one high-pressure port.
9 . The hydraulic drive system as claimed in claim 1 , configured to control the hydraulic cylinder with a constant total pressure in the hydraulic drive system.
10 . The hydraulic drive system as claimed in claim 1 , wherein, depending on a direction of rotation, hydraulic fluid is transferred between the first and second hydraulic cylinder surfaces through the second hydraulic machine.
11 . The hydraulic drive system as claimed in claim 1 , wherein the second hydraulic machine is configured as a 4-quadrant stage.
12 . The hydraulic system as claimed in claim 1 , wherein the second hydraulic machine has a first pressure port and a second pressure port, each rated for full working pressure, the first pressure port being directly hydraulically connected to the first hydraulic cylinder side and the second pressure port being directly hydraulically connected to the second hydraulic cylinder side.

Description

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. Hydraulic drive systems are used in many types of industrial applications. Generic hydraulic drive systems can be found in forming technology systems such as presses, rolling mills and generally in the construction of hydraulic units. A drive system with two mechanically coupled hydraulic machines is known from publication DE 10 2010 020 690 A1. These hydraulic machines are driven by a primary drive. In the hydraulic drive system shown, two hydraulic machines are driven conjointly at variable speeds by one motor via a drive shaft. The motor is configured as an electric motor. Said electric motor can be operated at a variable speed and with a variable direction of rotation. The two hydraulic machines of said hydraulic drive system are each fluidically connected via a hydraulic port to a respective side of the hydraulic cylinder and thus to the corresponding hydraulic cylinder surface, as well as to a reservoir. The two hydraulic machines can be arranged on the drive shaft in such a way that one of the two hydraulic machines functions as a pump and the other hydraulic machine functions as a motor. For example, the first hydraulic machine can provide the functionality of a pump for a clockwise direction of rotation, and the second hydraulic machine functions as a motor. By changing the direction of rotation of the hydraulic machine so that it is driven counterclockwise, the first hydraulic machine assumes the functionality of a motor, and the second hydraulic machine functions as a pump. The problem with the solution described in DE 10 2010 020 690 A1 is that the conveyed or displaced volume of the two mechanically coupled hydraulic machines must be precisely adapted to the cylinder surface ratio. This leads to a very limited possibility of use, since neither the hydraulic machines having a defined conveyed or displaced volume nor the cylinder rod or piston rod diameter can be varied in an arbitrary manner. The cylinder surface ratio is usually determined by the drive task and its general parameters. Hydraulic machines are available with a fixed, graduated conveyed or displaced volume, respectively. If the delivery volume of the two hydraulic machines is not precisely adapted to the cylinder surface ratio, there will be a total pressure increase over the cylinder stroke. This increase in pressure leads to a lower useful power of the cylinder, since the cylinder chamber pressure level must not be arbitrarily high. Furthermore, the fixed connection between in each case one hydraulic machine and a cylinder chamber means that, when using a differential cylinder with an exemplary surface ratio of 2:1, one hydraulic machine has a delivery volume that is twice as large as the other and must be of a correspondingly large configuration. This has an impact on the space required and the costs of the drive system shown. Furthermore, a hydraulic drive system with a hydraulic machine in a radial piston design with control pins is known from publication EP 292 1700 A1. The hydraulic machine is driven by a variable-speed motor. The hydraulic machine has at least three hydraulic ports, whereby the delivery volume of the hydraulic ports is determined by the control pin. The delivery volume is the volume of hydraulic fluid that flows through the cross section of a component per revolution of the motor. A solution to the differential cylinder adjustment is solved in this publication via the mentioned control pin of the hydraulic machine. The solution presented in the publication EP 292 1700 A1 also results in the problem that the control pin must be precisely adapted to the cylinder surface ratio. This consequently means that the total pressure varies depending on the cylinder stroke. Furthermore, variable-displacement pumps are known in the prior art. In hydraulic drive systems, a hydraulic cylinder is operated by at least two hydraulic machines, whereby at least one hydraulic machine is a variable-displacement pump. In a variable-displacement pump, the adjustment of the stroke ring and thus the vane of the variable-displacement pump is moved via a hydraulic cylinder. This cylinder must be pressurized and impinged with hydraulic fluid, resulting in the need for a proportional valve to control the cylinder. This results in a high level of structural and design-related complexity. Furthermore, a control system is necessary for this cylinder, which leads to an increased energetic problem since a constant pressure system which supplies this proportional valve is required. Therefore, a variable-displacement pump is inefficient and correspondingly complicated in terms of its structure and supply and, due to the other components, is maintenance-prone and less reliable and is expensive to procure, maintain and repair. When operating