Hydraulic system for a mobile work machine

Abstract

The present invention relates to a hydraulic system (100) for a mobile work machine which comprises a first hydraulic circuit (30) and a second hydraulic circuit (40), wherein: the first hydraulic circuit (30) comprises a first hydraulic machine (31) and a working hydraulics arrangement (32, 33) of the mobile work machine; the first hydraulic machine (31) is configured to supply pressure medium to the working hydraulics arrangement (32, 33); the second hydraulic circuit (40) comprises a second hydraulic machine (41) and a traction hydraulics arrangement (42) of the mobile work machine (42); the second hydraulic machine (41) is configured to supply pressure medium to the traction hydraulics arrangement (42) of the mobile work machine; the supply of pressure medium to the working hydraulics arrangement (32, 33) and to the traction hydraulics arrangement (42) takes place in the open hydraulic circuit; the working hydraulics arrangement (32, 33) is provided with at least one hydraulic consumer (33); and the traction hydraulics arrangement (42) is provided with at least one third hydraulic machine (42), which is used for the advancing movement of the mobile work machine, wherein a valve device (98, 99) is present between the first and the second hydraulic circuit and is configured to enable and prevent a hydraulic connection between the first and the second hydraulic circuit (30, 40).

Description

[0001] R.415636

[0002] Robert Bosch GmbH

[0003] 415636 DE - Tagliabue

[0004] OPEN-CIRCUIT HYDRAULIC SYSTEM

[0005] TECHNICAL AREA

[0006] The invention relates to a hydraulic system for a mobile work machine, comprising drive hydraulic components and working hydraulic components. The invention further relates to a method for controlling the hydraulic system, a control unit, a computer program, and a machine-readable storage medium.

[0007] STATE OF THE ART

[0008] In modern mobile machinery, the optimal utilization of energy from the energy generator (e.g., combustion engine or electric drive) presents a key challenge. Particularly in machines that must perform both driving and working functions, the integration of hydraulic systems is subject to specific technical requirements (see, for example, patent specification 10 2021 208 118 A1). A frequently observed limitation is that in existing systems, the pressure level in the overall machine is determined by either the working hydraulics or the driving hydraulics. This limitation leads to suboptimal operating scenarios that can negatively impact the overall efficiency of the machine.

[0009] A typical example of this problem arises in the configuration of systems with a single hydraulic pump, where its hydraulic pressure level is determined by the maximum required pressure of the working hydraulics and the travel hydraulics. In such cases, the required travel pressure may be higher than the working pressure, necessitating a reduction in pressure at the pressure carriage of the main control valve (MCV). This, in turn, impairs the efficiency of the mobile work machine.

[0010] An example of this can be found in patent application DE 10 2021 208 118 A1.

[0011] In contrast, the invention is based on the objective of producing a device that will overcome the disadvantages listed above.

[0012] Page 1 of 12 R.415636

[0013] SUMMARY

[0014] According to one embodiment of the present invention, a hydraulic system (100) is provided for a mobile working machine, comprising a first (30) and a second (40) hydraulic circuit, wherein the first hydraulic circuit (30) comprises a first hydraulic machine (31) and working hydraulics (32, 33) of the mobile working machine, wherein the first hydraulic machine (31) is configured to supply the working hydraulics (32, 33) with hydraulic fluid, wherein the second hydraulic circuit (40) comprises a second hydraulic machine (41) and driving hydraulics (42) of the mobile working machine, wherein the second hydraulic machine (41) is configured to supply the driving hydraulics (42) of the mobile working machine with hydraulic fluid, wherein the hydraulic fluid supply to the working hydraulics (32, 33) and the driving hydraulics (42) takes place in an open hydraulic circuit, wherein the working hydraulics (32,33) is provided with at least one hydraulic consumer (33) and wherein the drive hydraulics (42) is provided with at least one third hydraulic machine (42) used for propelling the mobile working machine, wherein a valve device (98, 99) is provided between the first and the second hydraulic circuit, which is configured to enable and prevent a hydraulic connection between the first and the second hydraulic circuit (30, 40), so that the first hydraulic circuit (30) and the second hydraulic circuit (40) can operate independently of each other as long as the valve device (98, 99) prevents a connection between the circuits,

[0015] The invention presented here offers an innovative solution to the problem described above by dividing the hydraulic machines (or hydraulic pumps) for driving and working functions into two separate circuits. This division allows the pressure levels in the two circuits to be controlled and optimized independently. This means that the driving hydraulics and the working hydraulics can each be operated at their optimal pressure ranges and limits without one system negatively affecting the other.

[0016] Another advantage of this dual-circuit solution is that cost-effective and proven components can be used in the working hydraulics, while the travel hydraulics are operated at higher, efficiency-optimized pressure limits. This not only enables more efficient use of the available energy but also improves the overall performance and lifespan of the machine.

[0017] Page 2 of 12 R.415636

[0018] This invention thus represents a significant advance in the development of hydraulically operated working machines, increasing both operational efficiency and flexibility in the choice of system components.

[0019] BRIEF DESCRIPTION OF THE FIGURES

[0020] The present invention is described with reference to the accompanying figures, where identical reference numerals refer to identical parts and / or to similar parts and / or to corresponding parts of the system. Regarding the figures:

[0021] Figure 1 schematically shows a circuit diagram of a drive system according to an embodiment of the present invention;

[0022] Figure 2 schematically shows a characteristic map of an embodiment of the hydrostatic drive according to an embodiment of the present invention;

[0023] Figure 3 schematically shows a circuit diagram of a drive system according to a further embodiment of the present invention.

[0024] DETAILED DESCRIPTION

[0025] The present invention is described below with reference to certain embodiments as shown in the accompanying figures. However, the present invention is not limited to the specific embodiments described in the following detailed description and shown in the figures; rather, the described embodiments merely illustrate some aspects of the present invention, the scope of which is defined by the claims.

[0026] Further modifications and variations of the present invention are obvious to a person skilled in the art. The present description therefore encompasses all modifications and / or variations of the present invention whose scope of protection is defined by the claims.

[0027] As shown in Figure 1, this invention discloses a hydraulic system 100 for a mobile working machine comprising a first 30 and a second 40 hydraulic circuit.

[0028] Page 3 of 12 R.415636

[0029] The first hydraulic circuit 30 comprises a first hydraulic machine 31, which in the illustrated example is a hydraulic pump (such as an axial piston pump) driven by a drive device 50, and a working hydraulic system 32, 33 of the mobile working machine. In particular, in this embodiment, the working hydraulic system is provided with two hydraulic consumers 33. Both hydraulic consumers 33 are, in this example, hydraulic cylinders responsible for the movement of one or more bodies, e.g., of a working kinematic system of the mobile working machine. However, it should be noted that the present invention can be applied with any type of working hydraulic system. For example, there may be only one hydraulic cylinder, or a hydraulic motor may be provided instead (e.g., for the rotary motion of a winch).

[0030] The first hydraulic machine 31 is configured to supply the working hydraulics 32, 33 with hydraulic fluid, with the hydraulic fluid supply to the working hydraulics 32, 33 taking place in an open hydraulic circuit. A main control valve (MCV) 32 is arranged in the working hydraulics 32, 33 between the hydraulic pump 31 and the consumers 33, and is configured to regulate the hydraulic fluid supply to the hydraulic consumers.

[0031] As also shown in Figure 1, the second hydraulic circuit 40 comprises a second hydraulic machine 41, which in the illustrated example is a hydraulic pump (such as an axial piston pump) driven by the drive device 50, and a drive hydraulic system 42 of the mobile working machine. In the illustrated example, the hydraulic pump 41 is driven together with the hydraulic pump 31 by the same drive device 50 (such as an electric or diesel motor). It should be noted that for this invention it is not necessary that both hydraulic pumps 31, 42 be driven by the same drive device 50. In this embodiment, the drive hydraulic system is equipped with two hydraulic motors 42.

[0032] The two hydraulic motors 42 are designed as adjustable and pivotable axial piston units, which serve as drive motors in ferry operation. For this purpose, the left motor 42 is rotationally fixed to the two left wheels or the sprocket of the mobile working machine, while the right motor 42 is rotationally fixed to the two right wheels or the sprocket of the mobile working machine. The four wheels or the two tracks are preferably not pivotable. Instead, for steering the mobile working machine, the two wheels or the track on one side are driven faster than the two wheels or the track on the other side. It is also possible that the two

[0033] The wheels or chain on one side are driven forward, while the hydraulic motor 42 on the other side pivots, driving the two wheels or chain on the other side in reverse. This allows the mobile work machine to navigate tighter turning radii or even rotate around its vertical axis. The first hydraulic machine 41 is configured to supply the drive hydraulics 42 with hydraulic fluid, with the hydraulic fluid supply to the drive hydraulics taking place in an open hydraulic circuit.

[0034] A valve device 98 is arranged between the first and second hydraulic circuits 30, 40. This valve device is configured to allow and prevent a hydraulic connection between the two circuits. Specifically, it is configured to allow a hydraulic connection between the first and second hydraulic circuits 30, 40 if the pressure in the first hydraulic circuit 30 is higher than the pressure in the second hydraulic circuit 40. In the illustrated example, the valve device 98 is configured to prevent the flow of hydraulic fluid from the second hydraulic circuit 40 into the first hydraulic circuit 30 under all circumstances. In this first embodiment, the valve device 98 is, in effect, a check valve. However, it should be noted that for this invention, it is not necessary for the valve device to be a check valve.Alternatively, the check valve 98 could be replaced by an orifice plate configured to perform the comparable functions of the check valve 98.

[0035] The connection of both hydraulic circuits 30 and 40 via the check valve 98 creates a one-way coupling that regulates the oil flow between the circuits. This one-way coupling allows a quantity of oil to be transferred from one circuit 30 to the other 40, but only in one direction. Since low pressures typically prevail in the working hydraulics, it is preferred that the direction of this one-way coupling is from the working hydraulics to the travel hydraulics. The check valve 98 then ensures that the circuits can operate independently of each other as long as the connection is not active. When necessary, the two circuits can be coupled by opening the check valve due to pressure in the working hydraulics. In situations where an additional oil quantity is required, the auxiliary pump 31 of the working hydraulics can be activated to supply the other circuit 40 as well.Since the pump 41 can be supported by the connection of both circuits with regard to the supplied oil quantity, it can be dimensioned smaller. A smaller pump not only reduces the...

[0036] Page 5 of 12 R.415636

[0037] This solution optimizes the use of hydraulic energy and improves machine efficiency, considering not only space requirements but also the cost and weight of the overall system.

[0038] According to a further embodiment of the present invention, the check valve 98 (or, for example, the described orifice) can be a lockable check valve (or a lockable orifice) via a predefinable signal. The lockable check valve 98 is configured, based on a control signal for the lockable check valve 98, to enable or prevent a hydraulic connection for the pressure medium from the first 30 to the second 40 hydraulic circuit (provided that the pressure in the first hydraulic circuit is higher than the pressure in the second hydraulic circuit, since otherwise the valve 98 would not open). The lockability of the valve allows the circuits to be connected or disconnected as needed, which greatly increases the flexibility of the system to adapt to driving and working conditions.

[0039] The input signal can be an electrical signal, and the input can come from an electronic control unit. The criteria for locking or unlocking the valve can be the flow rate requirement and / or the pressure levels or pressure level differences of the two hydraulic circuits 30 and 40, respectively, or prioritizations regarding the flow rate supply for the driving and working functions.

[0040] To better explain the logic of these embodiments, reference is made to Figure 2. Figure 2 shows a typical PQ curve, which illustrates the dependence of the maximum pressure on the volume flow rate based on the available power of the energy generator in a hydraulic system.

[0041] As shown, when there is a high flow rate requirement in hydraulic circuit 40, corresponding to a "high-speed" operation of the machine, the maximum possible pressure (P) of the second hydraulic machine 41 is reduced for performance reasons, because otherwise the required flow rate (Q) could not be achieved. During high-speed operation, precise work functions are generally not required or are minimally necessary. For this reason, the inventor conceived the idea that, in such a case, a feed from the first hydraulic circuit 30 into the second hydraulic circuit 30 could be permitted in order to increase the operating oil volume, thus enabling high-speed operation. This can be implemented in both embodiments. In the case of the check valve, the pump 31 can be controlled to a pressure above the pressure of the pump 41, resulting in an additional oil flow through the check valve.

[0042] Page 6 of 12 R.415636

[0043] Advantageously, the check valve allows the two hydraulic circuits 30 and 40 to be designed for different maximum pressure levels. This has a beneficial impact on the cost of the hydraulic components, the degree of freedom for the optimal design with regard to forces and flow requirements for the machine functions, and also on the continued reusability of already proven components when implementing the invention in the machine. If the working hydraulic circuit has a lower pressure level than the drive circuit 40, the high pressure level of the drive circuit cannot reach or impair the components of the working circuit 30.

[0044] The selectable locking of the check valve via a control unit can be advantageously used when driving and working functions are active simultaneously and no cross-influence is desired, regardless of the ratio of the two pressure levels in hydraulic circuits 30 and 40. This enforced circuit separation keeps the pressure levels different, allows them to be optimally selected for the respective function, and enables maximum energy utilization of the energy generator with minimal throttling losses in hydraulic circuits 30 and 40. This machine operating situation is particularly relevant during slower driving, where oil flow support for the driving circuit is not required.

[0045] It should be noted that the locking mechanism allows the advantages of the first embodiment to be retained while simultaneously preventing a hydraulic connection from occurring in certain undesired situations. The advantage of being able to select different pressure levels for the drive and working components is thus preserved.

[0046] Another possible embodiment is the use of this controllable one-sided circuit separation for two working circuits. Here, too, the advantages of summation and the separability of quantities and pressure levels can be beneficial for energy efficiency and for selecting the respective components with regard to nominal size and pressure resistance.

[0047] With reference to Figure 3, a further embodiment of the present invention will now be described. To avoid repetition, the differences from the other embodiments shown in Figure 1 will now be described. In this embodiment, the check valve 98 is replaced by a 4 / 3-way valve 98 with a closed default position. This valve is configured, based on a control signal, which can be hydraulic or electrical, to allow either (in the upper position) a flow of

[0048] Page 7 of 12 R.415636

[0049] to allow pressure medium from the first hydraulic circuit 30 to flow to the second hydraulic circuit 40 (and simultaneously prevent a flow of pressure medium from the second hydraulic circuit 40 to the first hydraulic circuit 30) or, in the lower position, to allow a flow of pressure medium from the second hydraulic circuit 40 to the first hydraulic circuit 30 (and simultaneously prevent a flow of pressure medium from the first hydraulic circuit 30 to the second hydraulic circuit 40) or, in the middle position, to prevent a flow of pressure medium between the first hydraulic circuit 30 and the second hydraulic circuit 40, thus separating the hydraulic circuits.

[0050] The advantage of this embodiment is that not only can the travel speed be increased at low pressure, but also the working functions benefit from the freedom of increasing the flow rate. This is because, in this embodiment, the flow of hydraulic fluid can occur in both directions. The two hydraulic machines 31 and 41 can therefore be designed to be smaller.

[0051] Furthermore, the proportionally adjustable valve 99 enables flexible summation even during simultaneous driving and working operations. In addition, the valve 99 allows the braking energy of the second hydraulic circuit 40 to be directly recuperated hydraulically in the first hydraulic circuit 30.

[0052] The described procedure for controlling the pumps 41, 31 and the valve 98, 99 is stored in the storage unit and is executed by the control unit.

[0053] The described method can be used in various types of machinery. Essentially, it can be used in all machinery with an electric or internal combustion engine. Examples of applications include excavators, telehandlers, forage harvesters, combine harvesters, snow blowers, and road milling machines.

[0054] While the present invention has been described with reference to the embodiments described above, it is clear to the person skilled in the art that it is possible to implement various modifications, variations and improvements of the present invention in light of the teaching described above and within the scope of the attached claims without deviating from the scope of protection of the invention.

[0055] Page 8 of 12 R.415636

[0056] Furthermore, the areas in which experts are likely to be knowledgeable have not been described here in order to avoid unnecessarily obscuring the described invention.

[0057] Accordingly, the invention should not be limited by the specific illustrative embodiments, but only by the scope of protection of the attached claims.

[0058] Page 9 of 12

Claims

R.415636 1. Hydraulic system (100) for a mobile working machine, comprising a first (30) and a second (40) hydraulic circuit, wherein the first hydraulic circuit (30) comprises a first hydraulic machine (31) and working hydraulics (32, 33) of the mobile working machine, wherein the first hydraulic machine (31) is configured to supply hydraulic fluid to the working hydraulics (32, 33), wherein the second hydraulic circuit (40) comprises a second hydraulic machine (41) and driving hydraulics (42) of the mobile working machine, wherein the second hydraulic machine (41) is configured to supply hydraulic fluid to the driving hydraulics (42) of the mobile working machine, wherein the hydraulic fluid supply to the working hydraulics (32, 33) and the driving hydraulics (42) is in an open hydraulic circuit, wherein the working hydraulics (32, 33) is provided with at least one hydraulic consumer (33) and wherein the driving hydraulics (42) is provided with at least one third hydraulic machine (42) is provided,which is used for the movement of the mobile working machine, wherein a valve device (98, 99) is provided between the first and the second hydraulic circuit, which is configured to enable and prevent a hydraulic connection between the first and the second hydraulic circuit (30, 40).

2. Hydraulic system (100) according to claim 1, wherein the valve device (98) is configured to allow a hydraulic connection between the first and second hydraulic circuits (30, 40) in the event that the pressure in the first hydraulic circuit (30) is higher than the pressure in the second hydraulic circuit (40).

3. Hydraulic system (100) according to claim 1 or 2, wherein the valve device (98) is configured to prevent a flow of pressure medium from the second hydraulic circuit (40) into the first hydraulic circuit (30) in any situation.

4. Hydraulic system (100) according to claim 3, wherein the valve device (98) is a lockable check valve, wherein the lockable check valve (98) is configured to enable or prevent a hydraulic connection for the pressure medium from the first (30) to the second (40) hydraulic circuit based on a control signal for the lockable check valve (98). Page 10 of 12 R.415636 5. Hydraulic system (100) according to claim 1 or 2, wherein the valve device (98, 99) is configured to enable or prevent a hydraulic connection between the first and the second hydraulic circuit (30, 40) based on a control signal.

6. Hydraulic system (100) according to claim 5, wherein the valve device (99) is configured, based on the control signal, either to allow a flow of pressure medium from the first hydraulic circuit (30) to the second hydraulic circuit (40), or to allow a flow of pressure medium from the second hydraulic circuit (40) to the first hydraulic circuit (30), or to prevent a flow of pressure medium between the first hydraulic circuit (30) and the second hydraulic circuit (40).

7. Method for controlling a hydraulic system (100) according to claim 4 or one of claims 5 to 6, wherein the method comprises the following step: a. Determining a pressure and / or volume flow requirement for the first hydraulic circuit (30) and for the second hydraulic circuit (40); b. Determining the control signal for the valve device (98, 99) based on the requirements determined in step a.

8. Control unit configured to execute a method according to claim 7.

9. Computer program configured to perform the method according to claim 5.

10. Machine-readable storage medium with a computer program stored thereon according to claim 9. Page 11 of 12

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