Fluid circuit

Abstract

The invention relates to a fluid circuit (1) for an electric axle drive (20) of a motor vehicle, wherein the fluid circuit (1) is designed such that, in a first operating mode, it suctions a fluid from a reservoir (4) and conducts said fluid along at least one component (10 to 14) of the electric axle drive (20) in order to absorb heat from the component (10 to 14) or to lubricate the component (10 to 14), and, in a second operating mode, it suctions fluid from the reservoir (4) and conducts said fluid to a hydraulic actuator (15) of the electric axle drive (20) in order to actuate the hydraulic actuator (15), and at the same time to interrupt the conducting of fluid along the at least one component (10 to 14).

Description

[0001] Fluid circuit

[0002] The invention relates to a fluid circuit for an electric axle drive of a motor vehicle.

[0003] It is known to actuate an actuator mechanically or by means of an electric motor. US2023 / 0323942 A1 discloses a drive device for a motor vehicle. The drive device comprises an electric machine with a transmission, wherein the motor vehicle can be electrically driven by the electric machine via the transmission. At least one gear of the transmission can be shifted by actuating a shift element. A medium is conveyed through a circuit that has a first branch through which the medium can be conveyed for cooling and / or lubricating the electric machine and / or the transmission, and a second branch through which the medium can be conveyed for actuating the shift element. A pump conveys the medium through the circuit. A third branch of the circuit allows the medium to flow for actuating the parking lock.

[0004] One object of the invention is to provide an alternative fluid circuit that enables the simple and cost-effective operation of a hydraulic actuator. This object is achieved by the subject matter of the independent claims. Advantageous embodiments are the subject of the dependent claims, the following description, and the figures.

[0005] The present invention proposes using a fluid circuit already present in an electric axle drive to temporarily actuate a hydraulic actuator, while briefly withholding fluid from the cooling and lubrication points. In other words, the actuator is integrated into the cooling circuit, and for the duration of the actuator's actuation, fluid is pumped only to the hydraulic actuator, not to the cooling and lubrication points. This is not a long-term measure, however, but rather, for example, only for a fraction of a second while the hydraulic actuator is used to engage a clutch claw. This ensures, firstly, that the cooling and / or lubrication of components of the electric axle drive is guaranteed. Secondly, the hydraulic actuator can be actuated with minimal additional parts and assembly effort.Therefore, no additional equipment (especially no mechanical or electrical equipment) is required to actuate the actuator. This helps to save costs for the entire device, particularly for the electric axle drive.

[0006] In this context, according to one aspect of the invention, a fluid circuit for an electric axle drive of a motor vehicle is disclosed. The fluid circuit is configured to draw in a fluid from a reservoir in a first operating mode and guide it along at least one component of the electric axle drive in order to absorb heat from the component or to lubricate the component.

[0007] The fluid circuit is further configured to draw fluid from the reservoir in a second operating mode and direct it to a hydraulic actuator in order to actuate the hydraulic actuator, while interrupting the flow of fluid along at least one component of the electric axle drive.

[0008] To promote and direct the fluid flow in the two operating modes, a pump and a main valve, particularly in the form of a directional control valve, can be used in a particularly simple and reliable manner. According to one embodiment, the pump is configured to draw the fluid from the reservoir and deliver it to the main valve and the hydraulic actuator. The main valve can be switched between an open and a closed state. In the first operating mode, the main valve is in the open state, allowing the fluid delivered by the pump to the main valve to flow through the main valve to at least one component, either to absorb heat from the component or to lubricate it.In the second operating mode, the main valve is in the closed state, so that fluid pumped from the pump to the hydraulic actuator actuates the hydraulic actuator, while no fluid pumped from the pump to the main valve passes through the main valve to the at least one component. The main valve can be hydraulically switched from the open to the closed state in an integrated design by means of a pilot valve. In a further embodiment, the fluid circuit includes a pilot valve, the pump being configured to draw fluid from the reservoir and deliver it to the pilot valve, and the pilot valve being capable of being switched between an open and a closed state. In the first operating mode, the pilot valve is in the closed state, as it has no influence on the switching state of the main valve.In the second operating mode, however, the pilot valve is in the open position, so that fluid pumped from the pump to the pilot valve is directed through the pilot valve to the main valve in such a way that the main valve is opened. The pilot valve is specifically an electromagnetically actuated 2 / 2-way valve, whereas the main valve is a hydraulically actuated 2 / 2-way valve.

[0009] Alternatively, in a modular design, the fluid circuit can comprise a pump and a main valve in the form of an electromagnetically actuated 2 / 2-way valve, wherein the pump is configured to draw fluid from the reservoir and deliver it to the main valve and the hydraulic actuator, and wherein the main valve can be switched between an open and a closed state. In the first operating mode, the main valve is electromagnetically opened, so that fluid delivered by the pump to the main valve passes through the main valve to at least one component to absorb heat from the component or to lubricate the component.In the second operating mode, the main valve is electromagnetically closed, so that fluid pumped from the pump to the hydraulic actuator actuates the hydraulic actuator, and during this time no fluid pumped from the pump to the main valve passes through the main valve to the at least one component. In this embodiment, a pilot valve is not required to open or close the main valve. In a further simplified design, the main valve can be configured as a changeover valve. Again, no pilot valve is required to open or close the main valve. The fluid circuit comprises a pump and a main valve in the form of an electromagnetically actuated 3 / 2-way valve.The pump is designed to draw fluid from the reservoir and deliver it to the main valve, which can be electromagnetically switched between a first and a second switching state. In the first operating mode, the main valve is electromagnetically switched to the first state, so that fluid delivered by the pump to the main valve does not flow to the hydraulic actuator, but instead to at least one component to absorb heat from the component or to lubricate it. In the second operating mode, the main valve is electromagnetically switched to the second state, so that fluid delivered by the pump to the main valve does not flow to the at least one component, but instead to the hydraulic actuator to actuate the hydraulic actuator.

[0010] The hydraulic actuator can include a piston valve which, in the second operating mode, can be moved from a retracted position to an extended position by the fluid supplied to the hydraulic actuator by the pump. The pilot valve, in turn, can have a locking element which can be moved into a locking position and an unlocking position, the locking element being configured to lock the piston valve in either the retracted or extended position. This allows the piston valve to be fixed in a predetermined position, particularly in the first and second operating modes, to prevent unwanted movement of the piston valve.

[0011] The hydraulic actuator can, for example, be configured to actuate a claw. Furthermore, the hydraulic actuator can be configured to actuate a sleeve. Actuating the hydraulic actuator can, in particular, operate a differential lock, a side axle disconnect, a parking lock, or a transmission. Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawing, where identical or similar elements are designated with the same reference numeral. Here, [the following is shown].

[0012] Fig. 1 shows a schematic of a fluid circuit with a hydraulic cylinder for actuating a claw according to a first embodiment of the invention, wherein the fluid circuit is in a first state,

[0013] Fig. 2 shows a schematic of the fluid cycle according to Fig. 1, wherein the fluid cycle is in a second state.

[0014] Fig. 3 shows a schematic of the fluid cycle according to Fig. 1, wherein the fluid cycle is in a third state.

[0015] Fig. 4 shows a schematic of a fluid circuit with a hydraulic cylinder for actuating a claw according to a second embodiment of the invention, wherein the fluid circuit is in a first state,

[0016] Fig. 5 shows a schematic of the fluid cycle according to Fig. 4, wherein the fluid cycle is in a second state,

[0017] Fig. 6 shows a schematic of the fluid cycle according to Fig. 4, wherein the fluid cycle is in a third state,

[0018] Fig. 7 shows a schematic of a fluid circuit with a hydraulic cylinder for actuating a claw according to a third embodiment of the invention, wherein the fluid circuit is in a first state,

[0019] Fig. 8 shows a schematic of the fluid circuit according to Fig. 7, wherein the fluid circuit is in a second state, Fig. 9 shows a schematic of the fluid circuit according to Fig. 7, wherein the fluid circuit is in a third state, and

[0020] Fig. 10 shows part of the scheme of the fluid circuit according to Fig. 3, where the claw is replaced by a sleeve.

[0021] Fig. 1 shows a fluid circuit 1 of an electric axle drive 20 of a motor vehicle (not shown in detail). The fluid circuit 1 comprises a pump 2, which draws a fluid, e.g., oil, from a reservoir 4, e.g., a tank, through a filter 3. The pump 2 delivers the drawn and filtered fluid into a supply line 5, which, in the embodiment shown in Figs. 1 to 3, is connected to a main valve 6, a pilot valve 7, and a hydraulic cylinder 15, which will be described in more detail below.

[0022] The main valve 6 is a hydraulically actuated switching valve (a 2 / 2-way valve according to Fig. 1). The pilot valve 7 can be electromagnetically switched to an open or closed state by energizing it (electrohydraulic actuator with linear piston actuation; a 2 / 2-way valve according to Fig. 1) in order to selectively switch the main valve 6 to an open or closed state. This can be described as an integrated design with piloted switching valve control. A first spring 27 biases the main valve 6 in the open switching state. A second spring 28 biases the pilot valve 7 in the closed switching state.

[0023] Fig. 1 shows the main valve 6 in the open switching state and the pilot valve 7 in the closed switching state. In this case, the pump 2 delivers the fluid via the open main valve 6, a heat exchanger 8, and a pressure filter 9 to various elements 10 to 14, i.e., cooling and lubrication points of the electric axle drive 20, in particular to wheelsets 10 of a 2-speed transmission 21 of the electric axle drive 20, as well as to a rotor 11, a first winding head 12, a second winding head 13, and a stator 14 of an electric drive machine 22 (in particular, an electric motor) of the electric axle drive 20. After the fluid has passed the aforementioned cooling and lubrication points 10 to 14, it is collected in the reservoir 4 and drawn back in by the pump 2, thus creating a closed fluid circuit 1.

[0024] Supply line 5 is also connected to hydraulic cylinder 15. Inside hydraulic cylinder 15, a piston slide 16 is mounted, which can be moved between an extended and a retracted position. A piston 17 is attached to one end face of the piston slide 16. The fluid delivered by pump 2 into supply line 5 can act on a hydraulically active surface of the piston 17 to move the piston slide 16 from the retracted position to the extended position. A third spring 29 pre-tensions the piston slide in the retracted position.

[0025] The piston valve 16 is mechanically connected to a claw 18. When the piston valve 16 is moved into the extended position, it moves the claw 18 into a closed position. When the claw 18 is in the closed position, as shown in Fig. 3, it can be used, for example, to engage a differential lock 30 or a side axle disconnect 31, to disengage a parking lock 32, or to engage a second gear of the transmission 21. Alternatively, it can also be used, for example, to actuate a dual-clutch transmission 33. When the piston valve 16 is moved into the retracted position, it moves the claw 18 into an open position, as shown in Fig. 1. In the open position of the claw 18, the following are possible: B. the differential lock 30 or the side axle separation 31 is opened, the parking lock 32 is engaged or the first gear of the transmission 21 is engaged.

[0026] The piston valve 16 can alternatively be mechanically connected to a sleeve 26 as shown in Fig. 10. When the piston valve 16 is moved into the extended position, it moves the sleeve 26 into a closed position. When the sleeve 26 is in the closed position, as shown in Fig. 10, it can be used, for example, to engage the differential lock 30 or the side axle disconnect 31, to disengage the parking lock 32, or to engage second gear in the transmission 21. Alternatively, it can also be used, for example, to actuate the dual-clutch transmission 33. When the piston valve 16 is moved into the retracted position, it moves the sleeve 26 into an open position. In the open position of the sleeve 26, the following are possible: B. the differential lock 30 or the side axle separation 31 is opened, the parking lock 32 is engaged or the first gear of the transmission 21 is engaged.

[0027] The pilot valve 7 includes a locking element 19, which can be moved into a locked position and an unlocked position depending on the switching state of the pilot valve 7. In the closed switching state of the pilot valve 7, the locking element 19 is in the locked position, so that the piston spool 16 is locked in either the extended or the retracted position. If, as shown in Fig. 1, the main valve 6 is in the open state and the pilot valve 7 is in the closed state, then no pressure builds up in the supply line 5 sufficient to move the piston spool 16 from the retracted to the extended position. Furthermore, the locking element 19 is in the locked position and blocks the movement of the piston spool 16 from the retracted to the extended position.

[0028] However, if – as shown in Fig. 2 – the pilot valve 7 is electromagnetically opened, in particular by energizing an electromagnet of the pilot valve 7, the locking element 19 is in the unlocked position and no longer blocks the movement of the piston spool 16 from the retracted to the extended position. Furthermore, the fluid pumped by the pump 2 into the supply line 5 can pass through the open pilot valve 7 to the main valve 6 and hydraulically close it. In this case, the fluid pumped by the pump 2 into the supply line 5 is not directed through the main valve 6 to the cooling and lubrication points 10 to 14. The supply of fluid to the cooling and lubrication points 10 to 14 is briefly interrupted.Instead, pressure can build up in the supply line 5, which acts on the hydraulically effective surface of the piston 17 to move the piston slide 16 from the retracted to the extended position. In the illustration according to Fig. 2, the pressure builds up still within the hydraulic cylinder 15, without the piston slide 16 having moved yet.

[0029] In the illustration according to Fig. 3, the pressure in the hydraulic cylinder 15 has already reached such a high value that the piston spool 16 has moved into the extended position and the claw 18 into the closed position. In this case, the claw 18 can be used, for example, to engage the parking lock 32. The energizing of the pilot valve 7 has ceased, so that the pilot valve 7 is again in the closed state, pre-tensioned by the second spring 28. This brings the locking element 19 into the locking position, such that the piston rod 17 is locked in the extended position and, for example, the parking lock 32 remains extended. Furthermore, no more fluid pumped by the pump 2 into the supply line 5 flows through the pilot valve 7 to the main valve 6, which is returned to the open switching state by means of the first spring 27.This allows the fluid pumped by pump 2 into supply line 5 to be directed back to the cooling and lubrication points 10 to 14 via the main valve 6.

[0030] The movement of the valve spool 16 from the retracted position to the extended position described above (and the associated movement of the claw 18 or the sleeve from the open to the closed position, which in turn leads to actuation of the switching elements 30 to 33 described above) can occur very quickly, e.g., in the millisecond range. The main valve 6 only needs to be closed for this short duration. Therefore, the flow of fluid to the cooling and lubrication points 10 to 14 only needs to be interrupted for this short duration, which does not lead to an interruption of the fluid flow and does not adversely affect the cooling and / or lubrication of the cooling and lubrication points 10 to 14.

[0031] Figures 4 to 6 show a modification of the fluid circuit 1 according to Figures 1 to 3 with an alternative main valve 6' and pilot valve 7'. In the embodiment according to Figure 4, the pilot valve 7' is not hydraulically connected to either the supply line 5 or the main valve; that is, no fluid pumped by the pump 2 into the supply line 5 can pass through the pilot valve 7' to the main valve 6' to switch it. The pilot valve 7' merely fulfills the interlocking function explained in connection with Figures 1 to 3. Instead, the main valve 6' can be directly actuated electromagnetically by a energized current (without the need for a pilot valve) to be switched either to the closed or the open state. This corresponds to a simplified design of the main valve 6' and pilot valve 7'.

[0032] When the main valve 6' is in the open switching state according to Fig. 4, the pump 2 delivers the fluid via the open main valve 6, the heat exchanger 8, and the pressure filter 9 to the various cooling and lubrication points 10 to 14 of the electric axle drive 20, as explained in conjunction with Figs. 1 to 3. The pilot valve 7' is not energized and locks the piston spool 16 in the retracted position.

[0033] In the switching state shown in Fig. 5, the electromagnets of the main valve 6' and the pilot valve 7' are energized, causing the main valve 6' to close and the locking element 19 of the pilot valve to move to the unlocked position. In this case, the fluid pumped by the pump 2 into the supply line 5 is not routed via the main valve 6 to the cooling and lubrication points 10 to 14. The flow of fluid to the cooling and lubrication points 10 to 14 is briefly interrupted. Instead, pressure can build up in the supply line 5, which acts on the hydraulically effective surface of the piston 17 to move the piston spool 16 from the retracted to the extended position. In the illustration in Fig. 5, the pressure builds up in the hydraulic cylinder 15 before the piston spool 16 has moved.

[0034] In the illustration according to Fig. 6, the pressure in the hydraulic cylinder 15 has already reached such a high value that the piston spool 16 has moved into the extended position and the claw 18 into the closed position. In this case, the claw 18 can be used, for example, to engage the parking lock 32. The energizing of the pilot valve 7' and the main valve 6' has ceased, so that the pilot valve 7' is again in the closed switching state and the main valve 6' is again in the open switching state. This brings the locking element 19 into the locking position, so that the piston spool 17 is locked in the extended position and, for example, the parking lock 32 remains deployed. Furthermore, the fluid pumped by the pump 2 into the supply line 5 can be routed again via the main valve 6' to the cooling and lubrication points 10 to 14.

[0035] Figures 7 to 9 show a modification of the fluid circuit 1 according to Figures 4 to 6 with yet another alternative main valve 6". As in Figures 4 to 6, in the embodiment according to Figure 7 the pilot valve 7' is not hydraulically connected to either the supply line 5 or the main valve; that is, no fluid pumped by the pump 2 into the supply line 5 can pass through the pilot valve 7' to the main valve 6' to switch it. The pilot valve 7' merely fulfills the locking function explained in connection with Figures 1 to 3.

[0036] The main valve according to Figures 7 to 9 can be directly actuated electromagnetically by energizing the main valve 6' (without the need for a pilot valve). The main valve 6' according to Figures 4 to 6 is a 2 / 2-way valve that can be switched to either the closed or the open position. The main valve 6" according to Figures 7 to 9 is a 3 / 2-way valve (3 ports, 2 switching positions or states) that can be switched to either a first switching state or a second switching state. An inlet port 23 of the main valve 6" is connected to the supply line 5. A first outlet port 24 is connected to the cooling and lubrication points 10 to 14. A second outlet port 25 is connected to the hydraulic cylinder 15.Depending on the switching state of the main valve 6", the supply line 5 is connected either to the cooling and lubrication points 10 to 14 or to the hydraulic cylinder 15. This corresponds to a modular design with a main valve 6" acting as a changeover valve. When the main valve 6" is in the first switching position, shown in Figures 7 and 9, the pump 2 delivers the fluid via the open main valve 6", the heat exchanger 8, and the pressure filter 9 to the various cooling and lubrication points 10 to 14 of the electric axle drive 20, as explained in conjunction with Figures 1 to 3. The pilot valve 7' is not energized and locks the piston spool 16 in the retracted position (Figure 7) or in the extended position (Figure 9).

[0037] In the switching state shown in Fig. 8, the electromagnets of the main valve 6" and the pilot valve 7' are energized, so that the main valve 6" is switched to the second switching state and the locking element 19 of the pilot valve 7' is moved to the unlocked position. In this case, the fluid pumped by the pump 2 into the supply line 5 is not directed via the main valve 6" to the cooling and lubrication points 10 to 14. The flow of fluid to the cooling and lubrication points 10 to 14 is briefly interrupted. Instead, the fluid pumped by the pump 2 into the supply line 5 is directed via the main valve 6" to the hydraulic cylinder 15. Pressure builds up in the supply line 5, which acts on the hydraulically effective surface of the piston 17 to move the piston spool 16 from the retracted to the extended position. In the illustration shown in Fig.8 The pressure builds up in the hydraulic cylinder 15 without the piston valve 16 having moved yet.

[0038] In the illustration according to Fig. 9, the pressure in the hydraulic cylinder 15 has already reached such a high value that the piston spool 16 has moved into the extended position and the claw 18 into the closed position. In this case, the claw 18 can be used, for example, to engage the parking lock 32. The energizing of the pilot valve 7' and the main valve 6" is discontinued, so that the pilot valve 7' is again in the closed switching state and the main valve 6" is again in its first switching state. This brings the locking element 19 into the locking position, so that the piston spool 17 is locked in the extended position and, for example, the parking lock 32 remains extended. Furthermore, the fluid pumped by the pump 2 into the supply line 5 can be routed again via the main valve 6" to the cooling and lubrication points 10 to 14.

[0039] Reference sign

[0040] Fluid circuit

[0041] pump

[0042] filter

[0043] reservoir

[0044] Supply line

[0045] Main valve ' Main valve “ Main valve

[0046] Pilot valve ' Pilot valve

[0047] Heat exchanger

[0048] Pressure filter 0 Gearbox 1 Rotor 2 First winding head 3 Second winding head 4 Stator 5 Hydraulic cylinder 6 Piston slide 7 Piston 8 Claw 9 Locking element 0 Electric axle drive 1 Gearbox 2 Electric drive motor 3 Input connection 4 First output connection 5 Second output connection 6 Sleeve 7 First spring 8 Second spring Third spring Differential lock Side axle separation Parking lock Dual clutch transmission

Claims

Patent claims 1. Fluid circuit (1) for an electric axle drive (20) of a motor vehicle, wherein the fluid circuit (1) is configured to - in a first operating mode, to draw in a fluid from a reservoir (4) and guide it along at least one component (10 to 14) of the electric axle drive (20) in order to absorb heat from the component (10 to 14) or to lubricate the component (10 to 14), and - in a second operating mode, to draw fluid from the reservoir (4) and direct it to a hydraulic actuator (15) of the electric axle drive (20) in order to actuate the hydraulic actuator (15), and during this time to interrupt the flow of fluid along the at least one component (10 to (14).

2. Fluid circuit (1) according to claim 1, the fluid circuit (1) comprising - a pump (2) and - a main valve (6), wherein - the pump (2) is designed to draw fluid from the reservoir (4) and deliver it to the main valve (6) and to the hydraulic actuator (15), - the main valve (6) can be switched to an open and a closed switching state, - in the first operating mode the main valve (6) is in the open state, so that fluid pumped from the pump (2) to the main valve (6) passes through the main valve (6) to at least one component (10 to 14) to absorb heat from the component (10 to 14) or to lubricate the component (10 to 14), and - in the second operating mode the main valve (6) is in the closed state, so that fluid pumped from the pump (2) to the hydraulic actuator (15) actuates the hydraulic actuator (15), and during this time no fluid pumped from the pump (2) to the main valve (6) passes through the main valve (6) to the at least one component (10 to 14).

3. Fluid circuit (1) according to claim 2, the fluid circuit (1) further comprising a pilot valve (7), wherein - the pump (2) is designed to draw the fluid from the reservoir (4) and deliver it to the pilot valve (7), - the pilot valve (7) can be switched to an open and a closed switching state, - in the first operating mode the pilot valve (7) is in the closed state and - in the second operating mode the pilot valve (7) is in the open state, so that fluid pumped from the pump (2) to the pilot valve (7) is directed via the pilot valve (7) to the main valve (6) in such a way that the main valve (6) is opened.

4. Fluid circuit (1) according to claim 3, wherein - the pilot valve (7) is an electromagnetically actuated 2 / 2-way valve, and - the main valve (6) is a hydraulically actuated 2 / 2-way valve.

5. Fluid circuit (1) according to claim 1, the fluid circuit (1) comprising - a pump (2) and - a main valve (6') in the form of an electromagnetically actuated 2 / 2-way valve, wherein - the pump (2) is designed to draw fluid from the reservoir (4) and deliver it to the main valve (6') and to the hydraulic actuator (15), - the main valve (6') can be switched to an open and a closed switching state, - in the first operating mode the main valve (6') has been electromagnetically opened, so that fluid pumped from the pump (2) to the main valve (6') passes through the main valve (6') to at least one component (10 to 14) to absorb heat from the component (10 to 14) or to lubricate the component (10 to 14), and - in the second operating mode the main valve (6') has been electromagnetically closed, so that fluid pumped from the pump (2) to the hydraulic actuator (15) actuates the hydraulic actuator (15), and during this time no fluid pumped from the pump (2) to the main valve (6') passes through the main valve (6') to at least one component (10 to 14).

6. Fluid circuit (1) according to claim 1, the fluid circuit (1) comprising - a pump (2) and - a main valve (6") in the form of an electromagnetically actuated 3 / 2-way valve, wherein - the pump (2) is designed to draw the fluid from the reservoir (4) and deliver it to the main valve (6"), - the main valve (6") can be electromagnetically switched to a first switching state and to a second switching state, - in the first operating mode the main valve (6") has been electromagnetically set to the first state, so that fluid pumped from the pump (2) to the main valve (6") does not reach the hydraulic actuator (15) via the main valve (6"), but rather at least one component (10 to 14) in order to absorb heat from the component (10 to 14) or to lubricate the component (10 to 14), and - in the second operating mode the main valve (6") has been electromagnetically switched to the second state, so that fluid pumped from the pump (2) to the main valve (6") does not pass through the main valve (6") to the at least one component (10 to 14), but to the hydraulic actuator (15) in order to actuate the hydraulic actuator (15).

7. Fluid circuit (1) according to one of the preceding claims, wherein - the hydraulic actuator (15) comprises a piston valve (16) which, in the second operating mode, can be moved from a retracted position to an extended position by the fluid supplied by the pump (2) to the hydraulic actuator (15), - the pilot valve (7; 7') has a locking element (19) which can be moved into a locking position and into an unlocking position, and - the locking element (19) is designed to lock the piston slide (16) in the retracted or extended position.

8. Fluid circuit (1) according to one of the preceding claims, wherein the hydraulic actuator (15) is configured to actuate a claw (18).

9. Fluid circuit (1) according to one of the preceding claims, wherein the hydraulic actuator (15) is configured to actuate a sleeve (26).

10. Fluid circuit according to one of the preceding claims, wherein a differential lock (30), a side axle separation (31), a parking lock (32) or a transmission (21; 33) can be actuated by actuating the hydraulic actuator (15).

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