Hydraulic system with cooling circuit and machine tool

Abstract

The present invention relates to a hydraulic system 10 for supplying at least one hydraulic consumer 110 with at least one supply pump 12, a consumer connection 14, a return connection 16, a cooling circuit 18 and a tank T. The at least one cooling circuit 18 has a cooling pump 20, a circulating cooling line 22 connected to the tank T and a heat exchanger 24. The cooling pump 20 and the heat exchanger 24 are arranged in the circulating cooling line 22. Downstream of the cooling pump 20 and upstream of the heat exchanger 24, a branch line 26 connected to the consumer connection 14 branches off from the circulating cooling line 22 and the cooling circuit 18 has a switching valve 28. The switching valve 28 can be switched between a closed position 28.1 and an open position 28.2, whereby the circulating cooling line 22 is closed in the closed position 28.1, so that the cooling pump 20 is only connected to the branch line 26. In the open position 28.2, the cooling pump 20 is connected to the heat exchanger 24. Furthermore, the invention relates to a machine tool 100 with such a hydraulic system 10.

Description

[0001] The present invention relates to a hydraulic system with at least one cooling circuit and to a machine tool with such a hydraulic system.

[0002] Such hydraulic systems with a cooling circuit are known in the art, for example, from the subsequently published DE 10 2023 101 659 A1. These hydraulic systems typically comprise at least one supply pump, a tank, a consumer connection, and a return connection. A hydraulic consumer is connected to the consumer connection and the return connection and can thus be pressurized via the supply pump.

[0003] Particularly when used in a machine tool, the hydraulic system must fulfill a wide variety of conditions. Firstly, a constant volume flow at a largely constant system pressure is regularly required, for example to maintain the clamping pressure of a hydraulically operated clamping device for securing the workpiece. For example, a volume flow of approximately 2 l / min to 6 l / min must be guaranteed at a constant system pressure of 100 bar. Secondly, a further requirement is that the temperature of the hydraulic fluid is maintained within a specified range, for example, from 20 °C to 40 °C. For this purpose, the hydraulic system usually has a separate cooling circuit as a bypass cooling system with a cooling pump, a recirculating cooling line, and a heat exchanger.

[0004] Furthermore, additional functionalities may require a different peak flow rate during machine tool operation, for example, during a hydraulically controlled tool change. These dynamic additional flow rates must not lead to a critical drop in pressure supply to the other components of the machine tool, especially not to a drop in pressure supply to the clamping device.

[0005] It is known from the prior art to map these dynamic additional volume flows using hydraulic accumulators and a corresponding accumulator charging circuit. The disadvantage of such hydraulic accumulators is that they require regular maintenance, thus increasing the operating costs of the machine tool, especially if the hydraulic accumulators are completely drained during operation. Furthermore, the accumulator charging circuit also increases the complexity and thus the cost of the hydraulic system. An alternative is to drive the supply pump via an asynchronous motor with a frequency converter. However, this also increases the cost of the hydraulic system, and depending on the application, it may still be necessary to use a hydraulic accumulator, albeit a somewhat smaller one.

[0006] It is therefore the object of the present invention to provide a hydraulic system for supplying at least one hydraulic consumer, which meets the requirements in use and is simple in design and cost-effective.

[0007] The object is achieved with a hydraulic system according to claim 1 and a machine tool according to claim 13. Advantageous further developments are described in the dependent claims.

[0008] The hydraulic system according to the invention for supplying at least one hydraulic consumer has at least one supply pump, one consumer connection, a return connection, at least one cooling circuit, and a tank. The at least one supply pump is connected to the tank and the consumer connection, such that the consumer connection or a hydraulic consumer connected to the consumer connection can be pressurized via the at least one supply pump. The return connection is connected to the tank. The at least one cooling circuit has a cooling pump, a circulating cooling line connected to the tank, and a heat exchanger. The hydraulic system according to the invention is distinguished from the hydraulic systems known from the prior art in particular in that a branch line connected to the consumer connection branches off from the circulating cooling line downstream of the cooling pump and upstream of the heat exchanger.Furthermore, according to the invention, the cooling circuit comprises a first switching valve that can be switched between a closed position and an open position. The circulating cooling line is closed when the first switching valve is in the closed position, so that the cooling pump is only connected to the branch line when the first switching valve is in the closed position. When the first switching valve is in the open position, the cooling pump is also connected to the heat exchanger.

[0009] In other words, the cooling circuit can be deactivated by switching the first switching valve, whereby the cooling pump is no longer connected to the heat exchanger, but only to the branch line branching off from the circulating cooling line and thus to the consumer connection. Any increase in the temperature of the hydraulic fluid caused by deactivating the cooling circuit is negligible, since the cooling circuit is only deactivated via the first switching valve for a short time and solely to cover the dynamic additional volume flows. Thus, the cooling pump can be used briefly to prevent a drop in system pressure due to a requested peak volume flow, without causing an excessive increase in the temperature of the hydraulic fluid. This provides a particularly cost-efficient hydraulic system.

[0010] It is advantageous if a check valve opening in the flow direction toward the consumer connection is installed in the branch line. This prevents hydraulic fluid pumped by the supply pump from entering the circulation cooling line. Alternatively or additionally, it is also conceivable to design the first switching valve as a 3 / 2-way valve and not to provide a check valve in the branch line, so that the cooling pump is connected either to the heat exchanger or to the branch line, depending on the switching position of the first switching valve.

[0011] The first switching valve is expediently preloaded into the blocking position, for example via a spring. The hydraulic system preferably has a first control line connected to the consumer connection, wherein the pressure in the first control line is applied to the first switching valve on the control side. The system pressure present at the consumer connection is therefore reported via the first control line to the first switching valve, so that the valve is switched to the open position when the pressure exceeds the preload force. If there is a drop in system pressure, the first switching valve switches to the blocking position due to the preload, so that the cooling pump is only connected to the consumer connection via the branch line and thus ensures a constant system pressure.

[0012] Alternatively, the hydraulic system can have a controller, wherein the first switching valve is an electromagnetically controlled switching valve. The controller controls the first switching valve based on at least one determined parameter of the hydraulic system. The parameter can be, for example, a pressure determined via a sensor or else a volume flow. For this purpose, the hydraulic system preferably has at least one sensor, in particular a pressure sensor and / or a volume flow sensor, which is connected to the controller. The first switching valve can be preloaded into the blocking position, for example via a spring. Alternatively, the first switching valve can also be a switching valve that can be electromagnetically controlled on both sides and is controlled accordingly via the controller based on the at least one determined parameter of the hydraulic system.

[0013] It is advantageous if at least one supply pump is an adjustable pump. An adjustable pump is advantageous from an energy perspective.

[0014] Conveniently, the at least one supply pump has an adjustment device, wherein an adjustment line connected to the adjustment device branches off from the circulating cooling line between the first switching valve and the heat exchanger, and a bypass line connects the adjustment device to the tank. A hydraulic resistance, for example, an orifice plate or a nozzle, is preferably arranged in the bypass line. The adjustment device is preferably designed as an adjustment cylinder.

[0015] In this context, it is advantageous if a second switching valve is arranged in the adjustment line. The second switching valve can be switched between an open position and a closed position, with the adjustment line being open in the open position of the second switching valve and closed in the closed position of the second switching valve. The second switching valve can be designed as a proportional switching valve or a binary switching valve. Highly dynamic pressure control can be achieved via the second switching valve.

[0016] It can be advantageous here if the second switching valve is preloaded into the blocking position, for example via a spring. The hydraulic system preferably has a second control line connected to the consumer connection, wherein the pressure in the second control line is applied to the second switching valve on the control side. This enables particularly simple but efficient pressure control of the supply pump. If the system pressure drops, the second switching valve is switched to the blocking position and the pressure at the adjustment device is reduced via the bypass line so that the supply pump is regulated to maximum performance. At the same time, the cooling pump is only connected to the branch line via the first switching valve so that a stable system pressure is restored.

[0017] Alternatively, the second switching valve can be an electromagnetically controlled switching valve, which is controlled by the hydraulic system controller based on at least one determined parameter of the hydraulic system. As already explained above, the at least one parameter of the hydraulic system can be, for example, a pressure or a volume flow, and is reported to the controller via at least one sensor of the hydraulic system. It is conceivable that the second switching valve is preloaded into the blocking position, for example, via a spring, or is a switching valve that can be electromagnetically controlled from both sides.

[0018] In an alternative embodiment, the at least one supply pump can be designed as a directly electrically adjustable pump. This has the advantage that the second switching valve and the adjustment device can be omitted. It is advantageous if the directly electrically adjustable pump is controlled via the hydraulic system control system based on a determined parameter of the hydraulic system. As already explained above, it is expedient in this context if the hydraulic system has at least one corresponding sensor, for example, a pressure sensor, a volume flow sensor, or a combined pressure and volume flow sensor.

[0019] It is advantageous if the cooling pump is a gear pump. A gear pump is cost-effective, easy to maintain, and robust. Furthermore, it is advantageous if at least one supply pump is a radial piston pump. In particular, it is expedient if the radial piston pump is constructed from a plurality of pump elements, so that individual pump elements can be switched on and off to adjust the pump.

[0020] Furthermore, it is advantageous if the hydraulic system has a plurality of supply pumps, with each supply pump connected to the tank and the respective consumer connection. Depending on the design of the respective supply pump, corresponding adjustment lines with switching valves, bypass lines, or adjustment devices are provided. It can be advantageous to have a supply pump for each hydraulic consumer to be controlled.

[0021] Furthermore, the hydraulic system can also have a plurality of cooling circuits, with each cooling circuit preferably being assigned to a supply pump. Thus, for each supply pump circuit, an additional dynamic volume flow can be provided by the respective cooling pump by deactivating the respective cooling circuit.

[0022] Furthermore, the problem can be solved with a machine tool that has at least one hydraulic consumer and a hydraulic system as described above. The hydraulic consumer is connected to the consumer connection and the return connection of the hydraulic system. The machine tool can be, for example, a lathe, a milling machine, a machining center, a honing machine, or even a drilling machine.

[0023] The invention is explained in more detail below using exemplary embodiments shown in the figures. The figures schematically show: Fig. 1 shows a hydraulic circuit diagram of a machine tool with a hydraulic system according to a first embodiment; Fig. 2 shows a hydraulic circuit diagram of a machine tool with a hydraulic system according to a second embodiment; and Fig. 3 a hydraulic circuit diagram of a machine tool with a hydraulic system according to a third embodiment.

[0024] Fig. 1 shows a hydraulic circuit diagram of a machine tool 100 with a Fig. 1 shows the hydraulic consumer 110, which is only schematically indicated. The machine tool 100 can be, for example, a lathe. The hydraulic consumer 110 can be, for example, a hydraulically operated clamping device for a workpiece. The machine tool 100 further comprises a hydraulic system 10.

[0025] As shown, the hydraulic system 10 comprises a supply pump 12, a tank T, a consumer connection 14, a return connection 16, and a cooling circuit 18. The hydraulic consumer 110 is connected to the consumer connection 14 and the return connection 16. The supply pump 12 is connected to the tank T and the consumer connection 14, so that the hydraulic consumer 110 can be supplied with pressurized hydraulic fluid via the supply pump 12.

[0026] In order to keep the hydraulic fluid in a predetermined temperature range of, for example, 20 °C to 40 °C, the cooling circuit 18 has a cooling pump 20, a circulating cooling line 22 and a heat exchanger 24. As in Fig. As shown in Figure 1, the cooling pump 20 and the heat exchanger 24 are arranged in the circulating cooling line 22. Furthermore, the circulating cooling line 22 is connected to the tank T, so that the cooling pump 20 pumps heated hydraulic fluid through the heat exchanger 24, where it is cooled and then returned to the tank T. The cooling pump 20 is designed as a gear pump in this embodiment.

[0027] Between the cooling pump 20 and the heat exchanger 24, a branch line 26 branches off from the circulating cooling line 22. In other words, the branch line 26 branches off from the circulating cooling line 22 upstream of the cooling pump 20 and downstream of the heat exchanger 24. As Fig. As shown in Figure 1, the branch line 26 opens upstream of the supply pump 12 and is thus connected to the consumer connection 14. A check valve 30 is arranged in the branch line 26, opening in the flow direction toward the consumer connection 14 and preventing unwanted backflow via the branch line 26 to the heat exchanger 24.

[0028] A first switching valve 28 is arranged between the cooling pump 20 and the heat exchanger 24 in the circulating cooling line 22. In this exemplary embodiment, the first switching valve 28 is designed as a 2 / 2-way valve. In a blocking position 28.1 of the first switching valve 28, the circulating cooling line 22 is blocked, so that the cooling pump 20 is no longer connected to the heat exchanger 24, but only to the branch line 26. In an open position 28.2 of the first switching valve 28, the circulating cooling line 22 is open, and the cooling circuit 18 is thus activated, in that hydraulic fluid can be supplied to the heat exchanger 24 via the cooling pump 20.

[0029] In this exemplary embodiment, the first switching valve 28 is preloaded into the blocking position 28.1 by a spring 50. Furthermore, the first switching valve 28 can be pressurized on the control side via a first control line 32 and thus counter to the force of the spring 50. The first control line 32 is connected to the consumer connection 14, whereby the system pressure present at the consumer connection 14 is reported to the first switching valve 28 via the first control line 32. As shown, a pressure gauge 54 can also be provided to display the system pressure present at the consumer connection 14. It is conceivable that the first switching valve 28 and the check valve 30 are formed by a combined valve, for example by a 3 / 2-way valve.

[0030] In this exemplary embodiment, the supply pump 12 is designed as an adjustable radial piston pump. The supply pump 12 preferably comprises a plurality of pump elements that can be switched on and off as required. To adjust the delivery rate of the supply pump 12, the supply pump 12 has an adjusting device 38 and a bypass line 42 connecting the adjusting device 38 to the tank T. In this exemplary embodiment, the adjusting device 38 is designed as an adjusting cylinder. An orifice 44 is arranged in the bypass line 42, via which the adjusting device 38 is relieved to the tank T.

[0031] An adjustment line 40 branches off between the first switching valve 28 and the heat exchanger 24. The adjustment line 40 is connected to the adjustment device 38. A second switching valve 46 is arranged in the adjustment line 40 and can be switched between a blocking position 46.1 and an open position 46.2. The second switching valve 46 is preloaded into the blocking position 46.1 by a spring 52. On the control side, the system pressure present at the supply connection 14 is reported to the second switching valve 46 via a second control line 48. In this exemplary embodiment, the second switching valve 46 is designed as a 2 / 2-way valve. The second switching valve 46 can also be provided as a proportional valve. The second switching valve 46 is thus designed to dynamically regulate the adjustment device 38 depending on the system pressure present at the consumer connection 14.

[0032] The following describes the function of the device according to the invention and Fig. 1 illustrated hydraulic system 10 is explained.

[0033] During normal operation of the hydraulic system 10, a constant system pressure of, for example, 100 bar at a volume flow of, for example, 2 l / min to 6 l / min is present at the consumer connection 14 in order to maintain the necessary pressure at the hydraulic consumer 110 (e.g., a clamping pressure). The system pressure is reported to the first switching valve 28 via the first control line 32 on the control side, so that the valve is switched to the open position 28.2 against the force of the spring 50. The cooling circuit 18 is activated because the cooling pump 20 pumps hydraulic fluid to the heat exchanger 24 via the first switching valve 28, which is switched to the open position 28.2. The second switching valve 46 is subjected to the system pressure via the second control line 48 on the control side and against the force of the spring 52, whereby the pressure present in the adjustment line 40 and thus the delivery rate of the supply pump 12 is regulated via the adjustment device 38.

[0034] If an additional dynamic flow rate occurs, for example, due to a hydraulically operated tool change, this can lead to a drop in system pressure. However, the system pressure must not drop to a critical level where the required clamping pressure at hydraulic consumer 110 can no longer be maintained. Pressure drops of less than 10 bar, for example, may be tolerable.

[0035] If the system pressure drops significantly, this increased pressure drop is reported to the first switching valve 28 via the first control line 32, and the spring force of the spring 50 exceeds the pressure reported via the first control line 32. The first switching valve 28 thus switches from the open position 28.2 to the closed position 28.1, whereby the cooling pump 20 is only connected to the branch line 26. The check valve 30 opens, and the entire volume flow of the cooling pump 20 is applied to the consumer connection 14.

[0036] Furthermore, the pressure drop in the system pressure is reported to the second switching valve 46 via the second control line 48. The spring force of the spring 52 exceeds the pressure reported via the second control line 48, and the second switching valve 46 switches from the open position 46.2 to the closed position 46.1. The adjusting device 38 is relieved via the bypass line 42, and the supply pump 12 is thus regulated to its maximum output. The maximum volume flow of both pumps, namely the cooling pump 20 and the supply pump 12, is thus available at the supply connection 14.

[0037] As soon as the additional dynamic flow rate no longer occurs, the first switching valve 28 is switched back to the open position 28.2, thus reactivating the cooling circuit 18. Accordingly, the flow rate of the supply pump 12 is also controlled via the second switching valve 46 and the adjustment device 38.

[0038] In Fig. 2 shows a hydraulic circuit diagram of a second embodiment of a machine tool 100 with a hydraulic system 10 according to the invention. Only the differences to the Fig. 1 shown embodiment is explained.

[0039] The Fig. The embodiment shown in Figure 2 differs from that shown in Fig. 1 in the design of the first switching valve 28, the second switching valve 46, and the control of these two valves. In this embodiment, no control lines are provided to report the pressure at the supply connection 14 on the control side to the first switching valve 28 or the second switching valve 46. The first switching valve 28 in this embodiment is designed as an electromagnetic 2 / 2-way valve, wherein the first switching valve 28 is preloaded into the blocking position 28.1 by the spring 50. The second switching valve 46 in this embodiment is also designed as an electromagnetic 2 / 2-way valve, which is preloaded into the blocking position 46.1 by the spring 52.

[0040] The hydraulic system 10 has a controller 34 for energizing the electromagnets of the first switching valve 28 and the second switching valve 46, thus switching the first switching valve 28 to the open position 28.2 and the second switching valve 46 to the open position 46.2. Furthermore, the hydraulic system 10 has a sensor 36 that measures at least one parameter of the hydraulic system 10 and reports it to the controller 34 for controlling the first switching valve 28 and the second switching valve 46. The sensor 36 can be, for example, a pressure sensor, a volume flow sensor, or a combined pressure and volume flow sensor.

[0041] If the control system 34 receives a signal from sensor 36 indicating an additional dynamic volume flow, the first switching valve 28 is switched to the blocking position 28.1 by de-energizing the electromagnet. The cooling circuit 18 is deactivated, and the cooling pump 20 is only connected to the branch line 26. Accordingly, the second switching valve 46 is switched to the blocking position 46.1 by de-energizing the electromagnet, so that the adjusting device 38 is relieved via the bypass line 42 and the supply pump 12 is adjusted to its maximum flow rate.

[0042] As soon as the additional dynamic volume flow no longer occurs, the first switching valve 28 is switched back to the open position 28.2 by energizing the electromagnet, thus reactivating the cooling circuit 18. Accordingly, the volume flow of the supply pump 12 is also controlled by appropriately energizing the second switching valve 46 and the adjustment device 38.

[0043] in Fig. 3 shows a hydraulic circuit diagram of a third embodiment of a machine tool 100 with a hydraulic system 10 according to the invention. The following describes only the differences to the Fig. 2 shown embodiment is explained.

[0044] The supply pump 12 of the Fig.The embodiment shown in Figure 3 is designed as a directly electrically adjustable pump. Therefore, no second switching valve, no adjustment line, and no adjustment device are provided in this exemplary embodiment. The supply pump is directly connected to the controller 34 and is controlled based on the parameters measured by the sensor 36 such that the delivery rate is regulated conventionally during normal operation and to maximum delivery rate when an additional dynamic volume flow occurs. At the same time, when an additional dynamic volume flow occurs, the first switching valve 28 is switched to the blocking position 28.1 via the controller, so that the cooling pump 20 supplies pressure to the hydraulic consumer 110 exclusively via the branch line 26.

[0045] As soon as the additional dynamic volume flow no longer occurs, the first switching valve 28 is switched back to the open position 28.2 by energizing the electromagnet, thus reactivating the cooling circuit 18. Accordingly, the volume flow of the supply pump 12 is also controlled via a corresponding direct electrical adjustment.

[0046] Furthermore, it is in principle possible to combine the embodiments described above, for example, by pressurizing the first switching valve 28 via the respective control line on the control side, and by the second switching valve 46 being an electromagnetic switching valve controlled by the controller 34. It should therefore also be noted that the terms used herein, such as "first," "second," or "third," do not specify a specific order, but serve solely to distinguish the corresponding features. List of reference symbols 10 Hydraulic system 12 Supply pump 14 Consumer connection 16 Return connection 18 Cooling circuit 20 Cooling pump 22 Circulation cooling line 24 heat exchangers 26 branch line 28 first switching valve 28.1 Blocking position of the first switching valve 28.2 Open position of the first switching valve 30 Check valve 32 first control line 34 Control 36 sensors 38 Adjustment device 40 adjustment line 42 Bypass line 44 aperture 46 second switching valve 46.1 Blocking position of the second switching valve 46.2 Open position of the second switching valve 48 second control line 50 Spring of the first switching valve 52 Spring of the second switching valve 54 pressure gauges 100 machine tools 110 hydraulic consumers 112 hydraulic consumers T Tank

Claims

[1] Hydraulic system (10) for supplying at least one hydraulic consumer (110) with at least one supply pump (12), one consumer connection (14), one return connection (16), at least one cooling circuit (18) and one tank (T), wherein the supply pump (12) is connected to the tank (T) and the consumer connection (14), wherein the return connection (16) is connected to the tank (T), wherein at least one cooling circuit (18) comprises a cooling pump (20), a circulating cooling line (22) connected to the tank (T) and a heat exchanger (24), and wherein the cooling pump (20) and the heat exchanger (24) are arranged in the circulating cooling line (22), characterized by , that Downstream of the cooling pump (20) and upstream of the heat exchanger (24) a branch line (26) connected to the consumer connection (14) branches off from the circulating cooling line (22), wherein the cooling circuit (18) has a first switching valve (28), wherein the first switching valve (28) can be switched between a closed position (28.1) and an open position (28.2), wherein the circulating cooling line (22) is blocked in the closed position (28.1) of the first switching valve (28), so that the cooling pump (20) is only connected to the branch line (26) in the closed position (28.1) of the first switching valve (28), and wherein the cooling pump (20) is connected to the heat exchanger (24) in the open position (28.2) of the first switching valve (28). [2] Hydraulic system (10) according to claim 1, characterized by , that a check valve (30) opening in the direction of flow towards the consumer connection (14) is arranged in the branch line (26). [3] Hydraulic system (10) according to one of claims 1 or 2, characterized by, that the first switching valve (28) is biased into the closed position (28.1), and the hydraulic system (10) has a first control line (32) connected to the consumer port (14), wherein the pressure in the first control line (32) is applied on the control side to the first switching valve (28). [4] Hydraulic system (10) according to one of claims 1 or 2, characterized by , that the hydraulic system (10) has a control unit (34) and the first switching valve (28) is an electromagnetically controlled switching valve, wherein the control unit (34) controls the first switching valve based on at least one determined parameter of the hydraulic system (10), wherein the first switching valve (28) is preferably biased into the closed position. [5] Hydraulic system (10) according to any one of the preceding claims, characterized by , that at least one supply pump (12) is an adjustable pump. [6] Hydraulic system (10) according to claim 5, characterized by, that the at least one supply pump (12) has an adjusting device (38), and an adjusting line (40) connected to the adjusting device (38) branches off from the circulating cooling line (22) between the first switching valve (28) and the heat exchanger (24), and a bypass line (42) connects the adjusting device (38) to the tank (T). [7] Hydraulic system (10) according to claim 6, characterized by , that a second switching valve (46) is arranged in the adjustment line (40), wherein the second switching valve (46) is switchable between an open position (46.2) and a closed position (46.1), wherein the adjustment line (40) is open in the open position (46.2) of the second switching valve (46) and wherein the adjustment line (40) is closed in the closed position (46.1) of the second switching valve (46). [8] Hydraulic system (10) according to claim 7, characterized by, that the second switching valve (46) is biased into the closed position (46.1), and the hydraulic system (10) has a second control line (48) connected to the consumer port (14), with the pressure in the second control line (48) being applied to the control side of the second switching valve (46). [9] Hydraulic system (10) according to claim 7, characterized by , that the hydraulic system (10) has a control unit (34) and the second switching valve (46) is an electromagnetically controlled switching valve, wherein the control unit (34) controls the second switching valve (46) based on at least one determined parameter of the hydraulic system (10), wherein the second switching valve (46) is preferably biased into the closed position. [10] Hydraulic system (10) according to any one of the preceding claims 1 to 4, characterized by , that at least one supply pump (12) is a directly electrically adjustable pump. [11] Hydraulic system (10) according to any one of the preceding claims, characterized by that the cooling pump (24) is a gear pump and / or that at least one supply pump (12) is a radial piston pump. [12] Hydraulic system (10) according to any one of the preceding claims, characterized by , that the hydraulic system (10) has a plurality of supply pumps (12), each supply pump (12) being connected to the tank (T) and the consumer connection (14). [13] Machine tool (100) with at least one hydraulic consumer (110) and a hydraulic system (10) according to one of the preceding claims, wherein the hydraulic consumer (110) is connected to the consumer port (14) and the return port (16).

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