System with low pressure unit and external tank for increasing a pressure level in a hydraulic drive and corresponding system with a hydraulic drive

Abstract

The invention relates to a low-pressure unit (1) for raising a pressure level in a hydraulic drive (8). The low-pressure unit (1) comprises a tank pressure accumulator (2) for storing a hydraulic fluid at a desired pressure, a low-pressure accumulator (3) downstream of the tank pressure accumulator (2) for intermediate storage of the fluid, and a hydraulic pump (4) driven by a motor (5). According to the invention, the tank pressure accumulator (2), the low-pressure accumulator (3), and the pump (4) are hydraulically coupled to one another via a connecting block (6), and the connecting block (6) is designed such that the low-pressure unit (1) can be directly integrated into or connected to a main control block of the hydraulic drive (8) via the connecting block (6), or is already integrated into or connected to it.

Description

[0001] The invention relates to a system comprising a low-pressure unit and an external tank for raising a pressure level in a hydraulic drive according to claim 1 and a corresponding system with a hydraulic drive according to claim 6.

[0002] In conventional hydraulic drives, an additional external or separate unit is connected to raise or adjust the pressure level in a hydraulic drive. This unit supplies a hydraulic fluid, especially oil, to the hydraulic drive at a correspondingly desired pressure level. The use of an external unit requires the use of piping or hoses as a connecting element between the hydraulic drive and the separate unit for supplying the hydraulic fluid. This takes up additional space and thus reduces the compactness of the hydraulic drive. Furthermore, the pipe or hose connection represents an additional maintenance factor, as a continuous, trouble-free supply of the fluid at the desired pressure level to the hydraulic drive must be ensured.

[0003] DE 10 2005 110 880 A1 discloses a system according to the preamble of claim 1. Further relevant prior art can be found in DE 197 11 591 A1 or JP 2000 130 401 A. In contrast, the present invention is based on the object of providing a low-pressure unit for raising a pressure level in a hydraulic drive / servo-hydraulic axle, which eliminates the need for an additional external unit and the associated hoses / piping. Furthermore, a system comprising a hydraulic drive and the low-pressure unit according to the invention is to be created, the pressure level of which is adjusted without an external unit.

[0004] The first object is achieved by a system with a low-pressure unit and an external tank having the features of patent claim 1 and the second by a system having the features of patent claim 6. Advantageous embodiments and further developments of the respective invention are the subject of the subclaims.

[0005] The invention relates to a system with a low-pressure unit for raising a pressure level in a hydraulic drive. The low-pressure unit comprises a tank pressure accumulator for storing a hydraulic fluid at a desired pressure, a low-pressure accumulator downstream of the tank pressure accumulator for temporarily storing the fluid, and a hydraulic pump driven by a motor. The tank pressure accumulator, the low-pressure accumulator, and the pump are hydraulically coupled to one another via a connecting block, and the connecting block is designed such that the low-pressure unit can be directly integrated into or connected to a main control block of the hydraulic drive via the connecting block, or can be integrated into or connected to it.

[0006] In other words, a hydraulic fluid is stored in a tank pressure accumulator, which can be pumped into a low-pressure accumulator using a motor-driven hydraulic pump, where the fluid is then temporarily stored. The low-pressure unit consisting of the tank pressure accumulator, the low-pressure accumulator, and the pump has a further connecting block to which the aforementioned components are connected. Furthermore, the components are hydraulically coupled to one another via this connecting block, i.e. the hydraulic fluid flows between the tank pressure accumulator, low-pressure accumulator, and pump via the connecting block. The connecting block can be connected to a hydraulic drive or integrated directly into it.

[0007] This low-pressure unit, comprising a tank pressure accumulator, a low-pressure accumulator, and a pump, which are hydraulically coupled to one another via a connecting block that can be connected to a hydraulic drive, enables a compact arrangement of the components for raising the pressure level within the hydraulic drive. Direct integration or connection of the entire low-pressure unit to the hydraulic drive eliminates the need for an external unit for pressure level adjustment and additional hoses or pipes for connecting an external unit to the hydraulic drive. Ultimately, this saves installation space, effort, and costs.

[0008] In a further aspect of the invention, the connecting block of the low-pressure unit has a flange surface with hydraulic interfaces for connecting the low-pressure unit to the hydraulic drive, in particular to the main control block of the hydraulic drive.

[0009] In other words, a surface of the connecting block, via which the components tank pressure accumulator, low-pressure accumulator and pump are connected to one another, is designed as a flange surface / connecting surface / coupling surface. This flange surface has hydraulic interfaces / connections that represent the outputs and inputs of the hydraulic circuit of the low-pressure unit. The low-pressure unit is connected to the hydraulic drive, in particular to the main control block of the hydraulic drive, via the interfaces of the flange surface, whereby the hydraulic (pressure) circuit / low-pressure circuit of the low-pressure unit is connected to the hydraulic (pressure) circuit of the hydraulic drive. Due to the direct / immediate connection via the interfaces on the flange surface of the low-pressure unit, additional hose or pipe connections are no longer necessary.

[0010] According to the invention, the low-pressure unit has a plurality of (switching) valves, preferably in the form of solenoid valves, via whose positions the low-pressure unit can be switched between operation as a closed system, in which the pump conveys fluid / pressure medium at a desired pressure level from the tank pressure accumulator into the low-pressure accumulator, and operation as an open system, in which the pump conveys fluid from an externally connected tank into the low-pressure accumulator.

[0011] In other words, the low-pressure unit can be operated as a closed system or as an open system. When operated as a closed system, the respective switching valves in the low-pressure unit are switched in such a way that the pressure medium is or can be transported from the tank pressure accumulator via the motor-driven pump into the low-pressure accumulator. When the low-pressure unit is alternatively operated as an open system, the pressure medium is pumped from an externally connected tank into the low-pressure accumulator of the low-pressure unit via the pump. Thus, the externally connected tank of the open system replaces the tank pressure accumulator of the closed system.

[0012] For example, the tank accumulator can be disconnected from the circuit (during operation) for any maintenance / service work and replaced by the external tank for a specific period of time. Once the service work has been completed, the tank accumulator can be reconnected, thereby decoupling the external tank. This advantageously ensures easier servicing compared to permanently closed systems. Switching between the closed and open system can be implemented using a variety of valves. This switching is preferably possible while the low-pressure unit is in operation, i.e. the switching processes between closed and open system operation or the coupling (or decoupling) of the tank accumulator or the external tank are possible without shutting down the system (the pump).Furthermore, the predominantly closed operation of the low-pressure unit makes it difficult for the fluid / oil used as a pressure medium to oxidize and also makes it difficult for dirt (particles) to enter.

[0013] In a further preferred aspect of the invention, the low-pressure unit has a check valve which prevents the fluid from flowing back from the low-pressure accumulator to the pump.

[0014] In other words, a check valve, which is preferably located directly upstream of the low-pressure accumulator, ensures that the pressure medium conveyed by the pump does not flow back to it, thus ensuring efficient transport of the fluid to the low-pressure accumulator.

[0015] In a further preferred aspect of the invention, the low-pressure unit has a regulator, preferably designed as a two-point regulator, which switches off the pump after the desired pressure level in the hydraulic drive is reached and / or switches the pump on when the pressure falls below a predetermined level.

[0016] In other words, the low-pressure unit's pump is preferably switched on and driven by the motor if the pressure level in the hydraulic drive drops below or falls below a certain value. The pump remains switched off until the pressure level drops below the predetermined value again. This ensures that the low-pressure unit is only operated as long as an adjustment of the pressure level is necessary, thus saving energy. Furthermore, a more efficient and precise adjustment of the pressure level in the hydraulic drive is enabled.

[0017] According to the invention, depending on the position of the plurality of valves, the tank pressure accumulator and the low-pressure accumulator can be filled with fluid from the externally connected tank, or the tank pressure accumulator and the low-pressure accumulator release fluid to the external tank or fluid from the tank pressure accumulator and the low-pressure accumulator can be absorbed by the externally connected tank.

[0018] Accordingly, by actuating / switching the valves accordingly, it is not only possible to switch between open and closed operation of the low-pressure unit, but also to empty the low-pressure accumulator and the tank pressure accumulator into the externally connected tank or to charge / store / feed the tank pressure accumulator with fluid from the external tank, depending on which function is desired. Recharging the tank pressure accumulator is particularly necessary if the pressure of the pressure medium / fluid in the closed hydraulic (pressure) circuit has dropped (over time) or is too low. This advantageous embodiment of the low-pressure unit enables emptying / charging orReplacing the pressure medium using the externally connected tank without the additional effort of stopping operation or performing corresponding maintenance steps, since these steps can be easily initiated, preferably even during operation, simply by switching the corresponding valves.

[0019] In a further advantageous aspect of the invention, the low-pressure unit has an additional cooling unit and / or a filter unit and, depending on the position of the valves, can be switched between operation as the closed system, in which the pump conveys fluid at a desired pressure level from the tank pressure accumulator into the low-pressure accumulator, and operation with a closed cooling circuit and / or a closed filter circuit comprising the low-pressure accumulator, the pump and the cooling unit and / or the filter unit.

[0020] In other words, the advantageous embodiment of the low-pressure unit has a cooling unit / plate heat exchanger / cooler and / or filter unit that is connected to the (pressure) circuit of the low-pressure unit. By appropriately switching the plurality of valves, it is possible to create a closed cooling circuit and / or filter circuit via the (low-pressure) pump, with the help of which the fluid of the low-pressure circuit is cooled and / or filtered. If the low pressure in the system is too low, the cooling circuit and / or filter circuit is interrupted or decoupled and the low-pressure accumulator is refilled to its corresponding pressure level. Preferably, the activation or deactivation of the cooling circuit and / or filter circuit is possible during operation of the low-pressure unit. Accordingly, no additional step of shutting down or converting the corresponding components is necessary.

[0021] Since the low-pressure unit, and thus also the cooling circuit or filter circuit integrated therein, is directly integrated into or connected to the hydraulic drive or servo-hydraulic axle, the fluid in the closed low-pressure circuit also cools the main control block of the hydraulic drive during operation of the cooling circuit. The cooled or filtered fluid can also be distributed throughout the axle by drawing in fluid from the low-pressure circuit.

[0022] The invention further relates to a system having the features explained above, in which the low-pressure unit is additionally directly connected to / integrated into a main control block of a hydraulic drive.

[0023] The invention will now be explained in more detail using advantageous embodiments and with reference to the accompanying figures. The figures are merely schematic in nature and serve solely to facilitate understanding of the invention. It should be noted that the features of the individual embodiments can be interchanged and used in any combination. They show: Fig. 1 an exemplary isometric front view of a low-pressure unit, according to an advantageous embodiment, Fig. 2 an exemplary isometric rear view of the low-pressure unit, according to the advantageous embodiment of Fig. 1 , Fig. 3 a hydraulic circuit diagram of the low-pressure unit connected to a hydraulic drive according to an advantageous embodiment and the pressure medium flow when operated as a closed system, Fig. 4 a hydraulic circuit diagram of the Fig. 3 shown embodiment of the low-pressure unit and the pressure medium flow when operated as an open system, Fig. 5 a hydraulic circuit diagram of the Fig. 3 and 4 shown embodiment of the low-pressure unit, and the pressure medium flow when filling the tank pressure accumulator with fluid from an external tank, Fig. 6 a hydraulic circuit diagram of the Figures 3 to 5 shown embodiment of the low-pressure unit and the pressure medium flow when emptying the tank pressure accumulator and the low-pressure accumulator into the external tank, Fig. 7 a hydraulic circuit diagram of the Figures 3 to 6 shown embodiment of the low-pressure unit with an additionally connected cooling unit and the pressure medium flow during operation of an integrated cooling circuit.

[0024] The present invention and the advantageous embodiment are described below with reference to the figures.

[0025] Figure 1 shows an exemplary isometric front view of the system according to the invention with the low-pressure unit 1, according to an advantageous embodiment. The low-pressure unit 1 has a tank pressure accumulator 2 and a low-pressure accumulator 3. The pressure medium stored in the tank pressure accumulator 2 is conveyed from the tank pressure accumulator by a pump 4 driven by a motor 5 and guided into the pressure circuit connected to it, in particular into the low-pressure accumulator 3, and temporarily stored therein. The components tank pressure accumulator 2, low-pressure accumulator 3, and pump 4 are hydraulically coupled or firmly connected to one another via a connecting block 6, which is preferably cuboid-shaped here, thereby forming the hydraulic low-pressure circuit.

[0026] Figure 2 shows the isometric back view of the Figure 1illustrated low-pressure unit 1. In this view, a flange surface 7 is essentially visible as a direct connection surface / contact surface with a hydraulic drive, preferably with a main control block of the hydraulic drive 8. A plurality of interfaces are arranged on / at the flange surface 7, which are designed to directly connect the low-pressure circuit of the low-pressure unit 1 with the pressure circuit of the hydraulic drive 8.

[0027] Figure 3shows a hydraulic circuit diagram of the low-pressure unit 1, which is directly connected to the hydraulic drive 8, according to an advantageous embodiment, and the pressure medium flow when the low-pressure unit 1 is operated as a closed system. The low-pressure unit 1 has a tank pressure accumulator 2 for storing a fluid at a desired pressure. The pump 4, driven by the motor 5, pumps fluid from the tank pressure accumulator via open switching valves 9, 10 into the downstream low-pressure accumulator 3. When operated as a closed system, the other switching valves 11 and 12 are in the closed state, so that an externally connected tank 13 is decoupled from the low-pressure circuit and the fluid flows in the closed system. A (spring-loaded) check valve 14 prevents backflow of the fluid from the low-pressure accumulator 3 towards the pump 4 when operated as a closed system.Furthermore, the low-pressure unit 1 has further (spring-loaded) check valves 15, 16 and the check valve 17, via which any leakage flow from the pump 4 is discharged, preferably adjustable pressure relief valves 18, 19 and a pressure gauge 20.

[0028] Fig. 4 shows the hydraulic circuit diagram of the Figure 3 shown embodiment of the low-pressure unit 1 and the pressure medium flow when the low-pressure unit 1 is operated as an open system. All Figure 3The components of the low-pressure unit 1 shown are also shown in this figure. In this open system operation, the switching valves 9, 10 remain in the open position and the switching valve 12 remains in the closed state. However, the switching valve 11 is now in the open position, whereby the pump 4 draws fluid from the external tank 13 and pumps it into the low-pressure tank 3. During this open operation of the low-pressure unit 1, service work on the tank pressure accumulator 2 is possible without interrupting operation, since the tank pressure accumulator 2 is decoupled or uncoupled from the low-pressure circuit in the open system. A leakage flow flowing from a pump (not shown) of the hydraulic drive 8 can flow to the pump 4 via the open switching valves 9 and 10.

[0029] Figure 5 shows a hydraulic circuit diagram of the Figures 3 and 4shown embodiment of the low-pressure unit 1, and the pressure medium flow when the tank pressure accumulator 2 is filled with fluid from the external tank 13. The low-pressure unit 1 can be switched during operation such that the tank pressure accumulator 2 can be filled with new fluid / pressure medium from the externally connected tank 13 if the pressure of the fluid in the tank pressure accumulator 2 is too low. In this case, the switching valves 9, 11 and 12 are in an open state, whereas the switching valve 10 is blocked. The open position of the switching valve 12 opens the hydraulic flow path between the external tank 13 and the tank pressure accumulator 2, whereby the pump 4 can pump fluid from the external tank 13 into the tank pressure accumulator 2.

[0030] Figure 6 shows a hydraulic circuit diagram of the Figures 3 to 5shown embodiment of the low-pressure unit 1 and the pressure medium flow when emptying the tank pressure accumulator 2 and the low-pressure accumulator 3 into the external tank 13. In order to drain / empty fluid with a possibly too low pressure from the low-pressure unit 1, in particular from the tank pressure accumulator 2 and from the low-pressure accumulator 3, all switching valves 9, 10, 11 and 12 are open in open operation of the low-pressure unit 1, i.e. operation with the externally coupled tank 13. In this case, fluid can be drained simultaneously from the tank pressure accumulator 2 and the low-pressure accumulator 3 into the external tank 13.

[0031] Figure 7 shows a hydraulic circuit diagram of the Figures 3 to 6shown embodiment of the low-pressure unit 1 with an additional cooling unit 21, which is connected to the low-pressure circuit, here downstream of the pump 4, as well as the pressure medium flow during operation of the integrated cooling circuit. The cooling circuit shown is integrated in the low-pressure unit 1 and also runs through the connected hydraulic drive 8. The cooling circuit in the closed system can be switched on or off via the positions of the switching valves 9 to 12, ie the external tank 13 is decoupled during cooling. Compared to the operation of the low-pressure unit 1 as a closed system (see illustration in Figure 3), the switching valve 9 is open in a second position, which releases a fluid flow between the pump 4 and the integrated cooling circuit of the low-pressure unit 1. The positions of the remaining switching valves 10 to 12 do not differ from their respective positions in normal closed operation. Figure 3 . List of reference symbols

[0032] 1Low-pressure unit 2Tank pressure accumulator 3Low-pressure accumulator 4Pump 5Motor 6Connecting block 7Flange surface 8Hydraulic drive 9, 10, 11, 12(Switching) valve 13External tank 14, 15, 16, 17Check valve 18, 19Pressure relief valve 20Pressure gauge 21Cooling unit

Claims

1. System consisting of a low-pressure unit (1) for raising a pressure level in a hydraulic drive (8), having a pressurized accumulator tank (2) for storing a hydraulic fluid at a desired pressure, a low-pressure accumulator (3) downstream of the pressurized accumulator tank (2) for temporarily storing the fluid, and having a hydraulic pump (2) driven by a motor (5), wherein the pressurized accumulator tank (2), the low-pressure accumulator (3) and the pump (4) are hydraulically coupled to one another by way of a connecting block (6), wherein the connecting block (6) is designed in such a way that the low-pressure unit (1) is able to be integrated directly into / or connected to a main control block of the hydraulic drive (8) by way of the connecting block (6); and a tank (13) connected externally to the low-pressure unit (1), wherein the low-pressure unit (1) has a multiplicity of valves (9, 10, 11, 12) by way of the positions of which the low-pressure unit (1) is switchable between operation as a closed system in which the pump (4) conveys fluid at a desired pressure level from the pressurized accumulator tank (2) to the low-pressure accumulator (3), and an operation as an open system in which the pump (4) conveys fluid from the externally connected tank (13) to the low-pressure accumulator (3); wherein depending on the position of the valves (9, 10, 11, 12), the pressurized accumulator tank (2) and the low-pressure accumulator (3) are able to be filled with fluid from the external tank (13), or the pressurized accumulator tank (2) and the low-pressure accumulator (3) dispense fluid to the external tank (13).

2. System according to Claim 1, characterized in that the connecting block (6) has a flange surface (7) with hydraulic interfaces for connecting the low-pressure unit (1) to the hydraulic drive (8).

3. System according to Claim 1 or 2, characterized by a check valve (14) which prevents a return flow of the fluid from the low-pressure accumulator (3) to the pump (4).

4. System according to one of Claims 1 to 3, characterized by a two-point controller which switches off the pump (4) after reaching the desired pressure level in the hydraulic drive (8) and / or switches on the pump (4) when falling below a predetermined pressure level.

5. System according to one of Claims 1 to 4, characterized in that the low-pressure unit (1) has a cooling unit (21) and / or a filter unit and, depending on the position of the valves (9, 10, 11, 12), is switchable between the operation as the closed system in which the pump (4) conveys fluid at a desired pressure level from the pressurized accumulator tank (2) to the low-pressure accumulator (3), and an operation with a closed cooling circuit and / or a closed filter circuit from the low-pressure accumulator (3) of the pump (4) and the cooling unit (21) and / or the filter unit.

6. System according to one of the preceding claims, additionally comprising a hydraulic drive (8), wherein the low-pressure unit (1) is directly connected to / integrated in a main control block of the hydraulic drive (8).

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