Hydraulic circuit

Abstract

The invention relates to a hydraulic circuit 1 comprising a high-pressure port 2, a low-pressure port 3, a feed unit 4, and a pump system 5. The low-pressure port 3 is fluidically connected to the high-pressure port 2 by means of a series connection of the feed unit 4 and the pump system 5. The pump system 5 comprises a pump 6 for pumping a fluid, a shaft 7 for driving the pump, and an unlockable check valve system 8. In a first state, the pump pumps the fluid from a first pump port 6a to a second pump port 6b, through the check valve 8, and on to the high-pressure port. In a second state, the pump pumps the fluid from the second pump port 6b to the first pump port 6a and to a control port 8c of the check valve 8.The check valve 8 prevents fluid flow from the high-pressure port to the first pump port 6a and allows fluid flow from the first pump port 6a to the high-pressure port 2. Fluid flow from the high-pressure port 2 to the first pump port 6a can be enabled via the control port 8c. The feed unit 4 is configured to allow fluid flow from the low-pressure port 3 to the respective suction pump ports 6a and 6b and to prevent fluid flow from the respective discharge pump ports 6a and 6b to the low-pressure port 3. When pumping the fluid, the pump 6 exhibits a leakage flow up to the shaft 7. A pressure equalization line 9 connects the shaft 7 to the low-pressure port 3 to discharge the fluid from the shaft 7.

Description

[0001] The invention relates to a hydraulic circuit. State of the art

[0002] Hydraulic systems for pressure build-up and pressure reduction comprise a high-pressure port, a low-pressure port, a supply unit, a pump, and a pilot-operated check valve. In a first state, fluid is sucked in by the pump via the supply unit and the low-pressure port and conveyed through the check valve to the high-pressure port. This creates pressure build-up at the high-pressure port. In a second state, the fluid is conveyed via the supply unit and the low-pressure port to a control port of the check valve. This allows fluid to flow from the high-pressure port in the blocking direction of the check valve through the check valve. This creates pressure reduction at the high-pressure port.

[0003] In the second state, the fluid is pumped to the control port of the check valve until a predefined pressure is established at the control port. However, little to no fluid flows through the control valve. The pump only reliably maintains pressure as long as the pump is pumping fluid. Therefore, to maintain the pressure at the control valve, fluid must be continuously pumped through the pump. Currently, an additional line is required to drain the excess fluid. This additional line is located between the pump and the control port of the check valve.

[0004] It is an object of the invention to provide a hydraulic circuit which allows a targeted pressure build-up and pressure reduction at a high-pressure connection and minimizes the number of fluid lines of the hydraulic circuit.

[0005] This object is achieved by a hydraulic circuit according to independent claim 1.

[0006] The hydraulic circuit comprises a high-pressure connection, a low-pressure connection, a supply unit, and a pump system. The low-pressure connection is fluidly connected to the high-pressure connection by means of a series connection of the supply unit and the pump system. The pump system has a pump for conveying a fluid, a shaft for driving the pump, and at least one releasable check valve system. The pump is configured, in a first state, to convey the fluid from a first pump connection to a second pump connection, and in a second state, to convey the fluid from the second pump connection to the first pump connection. The check valve system is fluidly connected to the second pump connection at a first valve connection and to the high-pressure connection at a second valve connection.The check valve system is designed to prevent fluid flow from the second valve port to the first valve port and to allow fluid flow from the first valve port to the second valve port. The check valve system has a control port via which fluid flow from the second valve port to the first valve port can be released. The hydraulic circuit is designed to release fluid flow from the second valve port to the first valve port via the control port when the pump is in the second state. The supply unit is designed to allow fluid flow from the low-pressure port to the first pump port in a first state of the pump and to prevent fluid flow from the second pump port to the low-pressure port.The supply unit is configured to allow fluid flow from the low-pressure port to the second pump port in a second state of the pump and to prevent fluid flow from the first pump port to the low-pressure port. When the pump is conveying fluid, the pump exhibits a leakage flow toward the shaft. The shaft is connected to the low-pressure port by means of a pressure equalization line to discharge the fluid from the shaft. Alternatively or additionally, the check valve system exhibits a leakage flow between the control port and the first valve port when the pump is in the second state.

[0007] In the first state, the fluid is sucked in via the first pump connection from the low-pressure connection and transported via the second pump connection to the first valve connection. The supply unit prevents backflow of the fluid from the second pump connection to the low-pressure connection. The fluid is then transported through the check valve system to the second valve connection and the high-pressure connection. Thus, in the first state, fluid is transported from the low-pressure connection through the pump and the check valve system to the high-pressure connection, and the pressure of the fluid at the high-pressure connection is increased. Thus, fluid can be actively controlled and supplied to the high-pressure connection by controlling the pump. If the pump delivery is stopped, no more fluid flows from the low-pressure connection through the pump and the check valve system to the high-pressure connection.A backflow of the fluid from the high pressure connection through the pump to the low pressure connection is prevented by the check valve system.

[0008] In the second state, the fluid is sucked in from the low-pressure port via the second pump port and conveyed via the first pump port to the control port of the check valve system. The supply unit prevents backflow of the fluid from the first pump port to the low-pressure port. By building up pressure at the control port, the check valve system allows fluid to flow from the high-pressure port via the second valve port, the check valve system, and the first valve port. Thus, fluid can be actively and controllably discharged from the high-pressure port by controlling the pump, and the fluid pressure at the high-pressure port can be reduced.

[0009] During operation of the pump, a leakage flow of some of the pumped fluid occurs in the pump and / or in the check valve system. The leakage flow in the pump reaches the pump shaft and is discharged via a pressure equalization line to the low pressure connection. The leakage flow in the check valve system reaches the low pressure connection via the first valve connection. The leakage flow allows the pump to operate normally and pressure to be maintained at the control inlet without damaging the pump. Furthermore, no additional line is required to discharge the fluid during pressure build-up and pressure maintenance at the control connection. The pumped fluid for pressure build-up at the control connection is discharged via the leakage flow and / or the pressure equalization line to the low pressure connection. Since leakage flow occurs in every operating state of the pump, a pressure equalization line is required anyway.This eliminates the need for a line between the first pump port and the control port, reducing the complexity of the hydraulic circuit.

[0010] The subclaims preferably show further developments of the invention.

[0011] The check valve system preferably comprises at least a first check valve. The first check valve is connected to the first valve port at a first check valve port and to the second valve port at a second check valve port. The first check valve is designed to prevent fluid flow from the second check valve port to the first check valve port and to allow fluid flow from the first check valve port to the second check valve port. This allows efficient pressure buildup at the high-pressure port in a first state, since no further hydraulic elements representing hydraulic resistance are arranged between the first valve port and the second valve port.

[0012] Particularly preferably, the first check valve is designed to be releasable. The first check valve has a first check valve control port, via which a fluid flow from the second check valve port to the first check valve port can be released. The first check valve control port is fluidly connected to the control port. Thus, the function of the check valve system can be implemented using a single check valve, and the system complexity of the hydraulic circuit can be kept to a minimum.

[0013] Particularly preferably, the check valve has a displacement chamber, a piston, and a check element. The check element is configured to prevent fluid flow from the second check valve port to the first check valve port in a third state of the check element. The check element is configured to allow fluid flow from the second check valve port to the first check valve port in a fourth state of the check element. The piston is configured such that when fluid flows into the displacement chamber via the control port and fluid builds up pressure in the displacement chamber, the piston moves in a first direction and puts the check element into the fourth state. The check valve has a leakage flow between the check valve control port and the first check valve port across the displacement chamber.The above design of the displacement and piston eliminates the need for an additional line to evacuate the leakage flow. This simplifies the manufacture of the hydraulic circuit.

[0014] Advantageously, the check valve system comprises at least one first throttle. The first throttle is directly connected to the second valve port. The first check valve and the first throttle are fluidically connected in series. This allows a slower fluid flow from the high-pressure port through the throttle and the check valve system. The slower fluid flow makes it easier to control the fluid flow and thus pressure reduction at the high-pressure port.

[0015] Particularly advantageously, the check valve system comprises at least a second check valve and a third valve connection. The third valve connection is fluidly connected to the second pump connection. The second check valve is fluidly connected to the third valve connection at a third check valve connection and to the second valve connection at a fourth check valve connection. The second check valve is designed to prevent fluid flow from the fourth check valve connection to the third check valve connection and to allow fluid flow from the third check valve connection to the fourth check valve connection.

[0016] Thus, in the check valve system, a first hydraulic path between the first valve connection and the second valve connection, and a second hydraulic path between the third valve connection and the second valve connection can be designed separately from one another. The second hydraulic path only allows fluid to flow through the second check valve to the second valve connection and the high-pressure connection, thus building up pressure at the high-pressure connection. Likewise, fluid can be pumped to the high-pressure connection via the first hydraulic path and the first check valve, thus increasing pressure at the high-pressure connection. The fluidic parallel arrangement of the first check valve and the second check valve reduces fluidic resistance between the second pump connection and the high-pressure connection, and increases the efficiency of the hydraulic circuit.

[0017] The second hydraulic path prevents fluid from being discharged from the high-pressure port, thus reducing pressure. In the second state, the first hydraulic path allows fluid to flow from the high-pressure port via the first pilot-operated check valve to the first valve port, thus reducing pressure at the high-pressure port. This allows for controlled pressure reduction at the high-pressure port.

[0018] By arranging the first throttle between the second valve port and the second check valve port, fluid flow and thus pressure reduction at the high-pressure port via the first hydraulic path can be slowed in the second state. This improves the controllability of the pressure reduction at the high-pressure port during the second state. Furthermore, the efficiency of pressure buildup is increased because the fluid can flow from the first pump port to the high-pressure port, additionally via the second hydraulic path, without having to pass through a throttle.

[0019] Particularly preferably, the check valve system comprises a third check valve. The third check valve is fluidically connected to the second valve port at a fifth check valve port and fluidically connected to the second check valve port at a sixth check valve port. The third check valve is configured to prevent fluid flow from the fifth check valve port to the sixth check valve port and to permit fluid flow from the sixth check valve port to the fifth check valve port. The third check valve is fluidically arranged parallel to the first throttle.

[0020] In the first state, fluid flows through the first valve port, the first check valve, and the second valve port, increasing a pressure at the high pressure port. This fluid flow flows, between the first check valve and the second valve port, partly through the third check valve and partly through the first restrictor. This arrangement presents little fluid resistance to the fluid flow than if all of the fluid flow passed exclusively through the first restrictor. This arrangement improved the efficiency of the check valve system. In the second state, the third check valve prevents fluid flow from the fifth check valve port to the sixth check valve port. All of the fluid flow flows from the high pressure port, through the second valve port, the first restrictor, the first check valve, and the first valve port.Since the entire fluid flow between the second valve port and the first valve port flows through the first throttle, this entire fluid flow is slowed down. This simplifies control of the pressure reduction at the high-pressure port. Thus, this design allows both efficient pressure buildup and better control of the pressure reduction at the high-pressure port.

[0021] Advantageously, the check valve system comprises a second throttle, a fourth check valve, and a fifth check valve. The second throttle, the fourth check valve, and the fifth check valve are fluidically arranged between the first check valve and the first valve port. The fourth check valve is fluidically connected to the first check valve port at a seventh check valve port and to the first valve port at an eighth check valve port. The fourth check valve is configured to prevent fluid flow from the seventh check valve port to the eighth check valve port and to permit fluid flow from the eighth check valve port to the seventh check valve port. The fifth check valve is arranged antiparallel to the fourth check valve.The fifth check valve is fluidly connected to the first check valve port at a ninth check valve port and to the first valve port at a tenth check valve port. The fifth check valve is configured to prevent fluid flow from the tenth check valve port to the ninth check valve port and to allow fluid flow from the ninth check valve port to the tenth check valve port. The second throttle is fluidly arranged between the tenth check valve port and the second valve port and parallel to the fourth check valve.

[0022] In the first state, fluid flows from the first pump port, through the fourth check valve and the first check valve, to the high pressure port, and pressure at the high pressure port increases. The orientation of the fifth check valve prevents fluid flow via the fifth check valve and thus via the second restrictor in the first state. This allows for high efficiency in the first state, as no losses occur through the second restrictor. In the second state, fluid flows from the high pressure port to the first valve port, through the fifth check valve and the second restrictor. The fourth restrictor blocks fluid flow in the second state, and all fluid flows through the fifth check valve and the second restrictor. The second restrictor slows down fluid flow, making fluid flow easier to control in the second state.Thus, this embodiment allows, in the first state, an efficient pressure increase at the high-pressure port, and, in the second state, an easily controlled pressure reduction at the high-pressure port.

[0023] Particularly advantageously, the check valve system has a fourth valve connection, a pilot-operated sixth check valve, and a third throttle. The fourth valve connection is fluidly connected to the low-pressure connection. The sixth check valve is fluidly connected to the fourth valve connection at an eleventh check valve connection and to the second valve connection at a twelfth check valve connection. The sixth check valve is designed to prevent fluid flow from the twelfth check valve connection to the eleventh check valve connection and to allow fluid flow from the eleventh check valve connection to the twelfth check valve connection. The sixth check valve has a second check valve control connection, via which fluid flow from the twelfth check valve connection to the eleventh check valve connection can be released.The second check valve control port is fluidly connected to the control port.

[0024] In the first state, the fluid flows, at least via the first valve port and the second valve port, to the high-pressure port and increases a pressure at the high-pressure port. In this case, no fluid flows via the third throttle. In the second state, fluid flows from the first pump outlet via the control port to the second check valve control port. As a result, the sixth check valve allows fluid to flow from the high-pressure port via the second valve port and the fourth valve port to the low-pressure port and enables pressure reduction. In this case, the fluid also flows through the third throttle and is slowed down. This improves the controllability of the pressure reduction at the high-pressure port without impairing the efficiency of pressure build-up at the high-pressure port.

[0025] The hydraulic circuit preferably has a pressure relief valve. The pressure relief valve is connected to the high-pressure port at a first pressure relief valve port and to the low-pressure port at a second pressure relief valve port. The pressure relief valve is connected to the high-pressure port and the low-pressure port in parallel with the pump system and the supply unit. The pressure relief valve opens when there is excess pressure at the high-pressure port and allows fluid to flow directly from the high-pressure port to the low-pressure port until the excess pressure at the high-pressure port is relieved.

[0026] Particularly preferably, the supply unit comprises a seventh check valve and an eighth check valve. The seventh check valve is connected to a low-pressure port at a thirteenth check valve port and to the first pump port at a fourteenth check valve port. The seventh check valve is designed to prevent fluid flow from the fourteenth check valve port to the thirteenth check valve port and to allow fluid flow from the thirteenth check valve port to the fourteenth check valve port. The eighth check valve is connected to a low-pressure port at a fifteenth check valve port and to the second pump port at a sixteenth check valve port.The eighth check valve is configured to prevent fluid flow from the sixteenth check valve port to the fifteenth check valve port and to allow fluid flow from the fifteenth check valve port to the sixteenth check valve port. Thus, the functionality of the supply unit can be implemented reliably and using simple hydraulic elements. This reduces the complexity and manufacturing costs of the hydraulic circuit.

[0027] Advantageously, the supply unit is designed as a dual-pressure valve. This reduces the number of required components in the hydraulic circuit and allows for a more compact design.

[0028] Further details, advantages, and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawings. It shows: Fig. 1 is a schematic representation of a hydraulic circuit according to a first embodiment of the invention, Fig. 2 is a schematic representation of a hydraulic circuit according to a second embodiment of the invention, Fig. 3 is a schematic representation of a hydraulic circuit according to a third embodiment of the invention, Fig. 4 is a schematic representation of a hydraulic circuit according to a fourth embodiment of the invention, Fig. 5 is a schematic representation of a hydraulic circuit according to a fifth embodiment of the invention, Fig. 6 is a schematic representation of a hydraulic circuit according to a sixth embodiment of the invention, Fig. 7 is a schematic representation of a hydraulic circuit according to a seventh embodiment of the invention, Fig. 8 is a schematic representation of a hydraulic circuit according to an eighth embodiment of the invention, and Fig.9A schematic representation of a hydraulic circuit according to a ninth embodiment of the invention. Embodiments of the invention

[0029] Fig. 1 shows a schematic representation of a hydraulic circuit according to a first embodiment of the invention.

[0030] The hydraulic circuit 1 comprises a high-pressure connection 2, a low-pressure connection 3, a supply unit 4, and a pump system 5. The low-pressure connection 3 is fluidly connected to the high-pressure connection 2 by means of a series connection of the supply unit 4 and the pump system 5. The pump system 5 has a pump 6 for conveying a fluid, a shaft 7 for driving the pump 6, and a releasable check valve system 8. The pump 6 is configured, in a first state, to convey the fluid from a first pump connection 6a to a second pump connection 6b, and, in a second state, to convey the fluid from the second pump connection 6b to the first pump connection 6a. The check valve system 8 is fluidly connected to the second pump connection 6b at a first valve connection 8a and to the high-pressure connection 2 at a second valve connection 8b.The check valve system 8 is designed to prevent fluid flow from the second valve port 8b to the first valve port 8a and to allow fluid flow from the first valve port 8a to the second valve port 8b. The check valve system 8 has a control port 8c, via which fluid flow from the second valve port 8b to the first valve port 8a can be released. The hydraulic circuit 1 is designed to release fluid flow from the second valve port 8b to the first valve port 8a via the control port 8c when the pump 6 is in the second state. The supply unit 4 is designed to allow fluid flow from the low-pressure port 3 to the first pump port 6a in a first state of the pump 6 and to prevent fluid flow from the second pump port 6b to the low-pressure port 3.The supply unit 4 is configured to allow a fluid flow from the low-pressure port 3 to the second pump port 6b in a second state of the pump 6 and to prevent a fluid flow from the first pump port 6a to the low-pressure port 3. When pumping the fluid, the pump 6 experiences a leakage flow toward the shaft 7. The shaft 7 is connected to the low-pressure port 3 by means of a pressure equalization line 9 in order to discharge the fluid from the shaft 7.

[0031] In the first state, the fluid is sucked in via the first pump port 6a from the low-pressure port 3 and conveyed via the second pump port 6b to the first valve port 8a. The supply unit 4 prevents backflow of the fluid from the second pump port 6b to the low-pressure port 3. The fluid is then conveyed through the check valve system 8 to the second valve port 8b and the high-pressure port 2. Thus, in the first state, fluid is conveyed from the low-pressure port 3 through the pump 6 and the check valve system 8 to the high-pressure port 2, and the pressure of the fluid at the high-pressure port 2 is increased. Thus, fluid can be actively controlled and supplied to the high-pressure port 2 by controlling the pump 6. If the delivery of the pump 6 is stopped, no more fluid flows from the low-pressure port 3 through the pump 6 and the check valve system 8 to the high-pressure port 2.A backflow of the fluid from the high pressure connection 2, through the pump 6, to the low pressure connection 3 is prevented by the check valve system 8.

[0032] In the second state, the fluid is sucked in via the second pump port 6b from the low-pressure port 3 and conveyed via the first pump port 6a to the control port 8c of the check valve system 8. The supply unit 4 prevents a backflow of the fluid from the first pump port 6a to the low-pressure port 3. By building up pressure at the first control port 8c, the check valve system 8 allows a flow of fluid from the high-pressure port 2 via the second valve port 8b, through the check valve system 8 and the first valve port 8a. Thus, a fluid can be actively and controllably discharged from the high-pressure port 2 by controlling the pump 6, and a pressure of the fluid at the high-pressure port 2 can be reduced.

[0033] During operation of the pump 6, a leakage flow of a portion of the pumped fluid occurs in the pump 6 and / or in the check valve system 8. The leakage flow reaches the shaft 7 of the pump 6 and is discharged via a pressure equalization line 9 to the low-pressure port 3. The leakage flow in the check valve system 8 reaches the low-pressure port 3 via the first valve port 8a. The leakage flow allows the pump 6 to operate normally, and a pressure can be maintained at the control port 8c without damaging the pump 6. Thus, no line is required between the first pump port 6a and the control port 8c. This reduces the complexity of the hydraulic circuit 1.

[0034] The hydraulic circuit 1 has a pressure relief valve 19. The pressure relief valve 19 is connected to the high-pressure port 2 at a first pressure relief valve connection 19a and to the low-pressure port 3 at a second pressure relief valve connection 19a. The pressure relief valve 19 is connected to the high-pressure port 2 and the low-pressure port 3 in parallel to the pump system 5 and to the supply unit 4. The pressure relief valve 19 opens when there is excess pressure at the high-pressure port 2 and allows fluid to flow directly from the high-pressure port 2 to the low-pressure port 3 until the excess pressure at the high-pressure port 2 is relieved.

[0035] The supply unit 4 is designed as a dual-pressure valve 22. This reduces the number of required components in the hydraulic circuit 1 and allows for a more compact design of the hydraulic circuit 1.

[0036] Fig. 2 shows a schematic representation of a hydraulic circuit 1 according to a second embodiment of the invention.

[0037] The second embodiment from Fig. 2 is based on similar features as the first embodiment from Fig. 1 .

[0038] In addition, the check valve system 8 has a first pilot-operated check valve 10. The first pilot-operated check valve 10 is connected to the first valve port 8a at a first check valve port 10a and to the second valve port 8b at a second check valve port 10b. The first pilot-operated check valve 10 is designed to prevent fluid flow from the second check valve port 10b to the first check valve port 10a and to allow fluid flow from the first check valve port 10a to the second check valve port 10b. This allows for efficient pressure buildup at the high-pressure port 2 in the first state, since no further hydraulic elements representing hydraulic resistance are arranged between the first valve port 8a and the second valve port 8b.

[0039] The first pilot-operated check valve 10 has a first check valve control port 10c, via which a fluid flow can be released from the second check valve port 10b to the first check valve port 10a. The first check valve control port 10c is fluidly connected to the control port 8c. Thus, the function of the check valve system 8 can be implemented using a single check valve 10, and the system complexity of the hydraulic circuit can be kept low.

[0040] Fig. 3 shows a schematic representation of a hydraulic circuit 1 according to a third embodiment. The third embodiment is based on similar features to the second embodiment.

[0041] The check valve 10 has a displacement chamber 10f, a piston 10e, and a check element 10f. The check element 10f is configured, in a third state of the check element 10f, to prevent fluid flow from the second check valve port 10b to the first check valve port 10a. The check element 10f is configured, in a fourth state of the check element 10f, to allow fluid flow from the second check valve port 10b to the first check valve port 10a. The piston 10e is configured such that when fluid flows into the displacement chamber 10d via the control port 8c and fluid builds up pressure in the displacement chamber 10d, the piston 10e moves in a first direction and places the check element 10f into the fourth state. The check valve 10 has a leakage flow between the check valve control port 10c and the first check valve port 10a via the displacement 10d.The above design of the displacement and piston eliminates the need for an additional line to evacuate the leakage flow. This simplifies the manufacture of hydraulic circuit 1. Fig. 4 shows a schematic representation of a hydraulic circuit 1 according to a fourth embodiment of the invention. The fourth embodiment of Fig. 4 is based on similar features as the third embodiment from Fig. 3 .

[0042] The check valve system 8 also includes a first throttle 11. The first throttle 11 is directly connected to the second valve port 8b. The first check valve 10 and the first throttle 11 are fluidically connected in series. This allows a slower fluid flow from the high-pressure port 2 through the first throttle 11 and the first check valve 10. The slower fluid flow allows for easier control of the fluid flow and thus pressure reduction at the high-pressure port 2.

[0043] The check valve system 8 has a second check valve 12 and a third valve port 8d. The third valve port 8d is fluidically connected to the second pump port 6b. The second check valve 12 is connected to the third valve port 8d at a third check valve port 12a and to the second valve port 8b at a fourth check valve port 12b. The second check valve 12 is configured to prevent fluid flow from the fourth check valve port 12b to the third check valve port 12a and to permit fluid flow from the third check valve port 12a to the fourth check valve port 12b.

[0044] Thus, the check valve system 8 can be configured separately from one another, with a first hydraulic path between the first valve port 8a and the second valve port 8b, and a second hydraulic path between the third valve port 8d and the second valve port 8b. The second hydraulic path allows fluid flow only through the second check valve 12 to the second valve port 8b and the high-pressure port 2, thus building up pressure at the high-pressure port 2. Likewise, fluid can be conveyed to the high-pressure port 2 via the first hydraulic path via the first check valve 10, thus increasing pressure at the high-pressure port 2. The fluidic parallel arrangement of the first check valve 10 and the second check valve 12 reduces fluidic resistance between the second pump port 6b and the high-pressure port 2, and the efficiency of the hydraulic circuit 1 is increased.

[0045] No fluid can be discharged from the high-pressure port 2 via the second hydraulic path, thus reducing pressure. In the second state, the first hydraulic path allows fluid flow from the high-pressure port 2 via the first pilot-operated check valve 10 to the first valve port 8a, thus reducing pressure at the high-pressure port 2. This allows for controlled pressure reduction at the high-pressure port 2.

[0046] By arranging the first throttle 11 between the second valve port 8b and the second check valve port 10b, fluid flow and thus pressure reduction at the high-pressure port 2 via the first hydraulic path can be slowed in the second state. This improves the controllability of the pressure reduction at the high-pressure port 2 during the second state. Furthermore, the efficiency of the pressure buildup is increased because the fluid can flow from the first pump port 6a to the high-pressure port 2 via the second hydraulic path without having to pass through a throttle.

[0047] Fig. 5 shows a schematic representation of a hydraulic circuit according to a fifth embodiment of the invention. The fifth embodiment of Fig. 5 is based on similar features as the fourth embodiment from Fig. 4 .

[0048] The check valve system 8 also has a third check valve 13. The third check valve 13 is fluidically connected to the second valve port 8b at a fifth check valve port 13a and fluidically connected to the second check valve port 10b at a sixth check valve port 13b. The third check valve 13 is configured to prevent fluid flow from the fifth check valve port 13a to the sixth check valve port 13b and to permit fluid flow from the sixth check valve port 13b to the fifth check valve port 13a. The third check valve 13 is fluidically arranged parallel to the first throttle 11.

[0049] In the first state, fluid flows through the first valve port 8a, the first check valve 10, and the second valve port 8b, increasing pressure at the high pressure port 2. This fluid flow flows, between the first check valve 10 and the second valve port 8b, partly through the third check valve 13 and partly through the first throttle 11. This arrangement presents little fluid resistance to the fluid flow than if the entire fluid flow passed through the first throttle 11. This arrangement improved the efficiency of the check valve system 8. In the second state, the third check valve 13 prevents fluid flow from the fifth check valve port 13a to the sixth check valve port 13b. The entire fluid flow flows from the high pressure port 2, through the second valve port 8b, the first throttle 11, the first check valve 10, and the first valve port 8a.Since the entire fluid flow between the second valve port 8b and the first valve port 8a flows through the first throttle 11, this entire fluid flow is slowed down. This simplifies control of the pressure reduction at the high-pressure port. Thus, this embodiment allows both efficient pressure buildup and better control of the pressure reduction at the high-pressure port 2.

[0050] Fig. 6 shows a schematic representation of a hydraulic circuit according to a sixth embodiment of the invention. The sixth embodiment of Fig. 6 is based on similar features as the second embodiment from Fig. 2 and / or the third embodiment from Fig. 3 on.

[0051] The check valve system 8 has a second throttle 15, a fourth check valve 14, and a fifth check valve 16. The second throttle 15, the fourth check valve 14, and the fifth check valve 16 are fluidically arranged between the first check valve 10 and the first valve port 8a. The fourth check valve 14 is fluidically connected to the first check valve port 10a at a seventh check valve port 14b and to the first valve port 8a at an eighth check valve port 14a. The fourth check valve 14 is configured to prevent fluid flow from the seventh check valve port 14b to the eighth check valve port 14a and to permit fluid flow from the eighth check valve port 14a to the seventh check valve port 14b.

[0052] The fifth check valve 16 is arranged antiparallel to the fourth check valve 14. The fifth check valve 16 is fluidically connected to the first check valve port 10a at a ninth check valve port 16a and to the first valve port 8a at a tenth check valve port 16b. The fifth check valve 16 is designed to prevent fluid flow from the tenth check valve port 16b to the ninth check valve port 16a and to allow fluid flow from the ninth check valve port 16a to the tenth check valve port 16b. The second throttle 15 is fluidically arranged between the tenth check valve port 16b and the second valve port 8b and parallel to the fourth check valve 14.

[0053] In the first state, the fluid flows from the first pump port 6a, through the fourth check valve 14 and the first check valve 10, to the high-pressure port 2, and the pressure at the high-pressure port 2 increases. The orientation of the fifth check valve 16 prevents fluid flow via the fifth check valve 16 and thus via the second throttle 15 in the first state. This allows for high efficiency in the first state, as no losses occur through the second throttle 15. In the second state, the fluid flows from the high-pressure port 2 to the first valve port 8a, through the fifth check valve 16 and the second throttle 15. The fourth check valve 14 blocks the fluid flow in the second state, and all fluid flows through the fifth check valve 16 and the second throttle 15. The second throttle 15 slows down the fluid flow, making fluid flow easier to control in the second state.Thus, this embodiment allows an efficient pressure increase at the high-pressure connection 2 in the first state and an easily controlled pressure reduction at the high-pressure connection 2 in the second state.

[0054] Fig. 7 shows a schematic representation of a hydraulic circuit according to a seventh embodiment of the invention.

[0055] The seventh embodiment from Fig. 7 is based on similar features as the first embodiment from Fig. 1 .

[0056] In addition, the check valve system 8 has a first check valve 10, a fourth valve port 8e, a pilot-operated sixth check valve 18, and a third throttle 17. The first check valve 10 is connected to the first valve port 8a at a first check valve port 10a and to the second valve port 8b at a second check valve port 10b. The first check valve 10 is configured to prevent fluid flow from the second check valve port 10b to the first check valve port 10a and to permit fluid flow from the first check valve port 10a to the second check valve port 10b.

[0057] The fourth valve port 8e is fluidically connected to the low-pressure port 3. The sixth check valve 18 is fluidically connected to the fourth valve port 8e via an eleventh check valve port 18a and to the second valve port 8b via a twelfth check valve port 18b. The sixth check valve 18 is designed to prevent fluid flow from the twelfth check valve port 18b to the eleventh check valve port 18a and to allow fluid flow from the eleventh check valve port 18a to the twelfth check valve port 18b. The sixth check valve 18 has a second check valve control port 18c, via which fluid flow from the twelfth check valve port 18b to the eleventh check valve port 18a can be released. The second check valve control port 18c is fluidically connected to the control port 8c.

[0058] In the first state, the fluid flows via the first valve port 8a and the second valve port 8b through the first check valve to the high-pressure port 2 and increases a pressure at the high-pressure port 2. In this case, no fluid flows via the third throttle 17 or any other throttle. In the second state, the first check valve 10 prevents a fluid flow from the second valve port 8b to the first valve port 8a. The fluid flows from the first pump outlet 6a via the control port 8c to the second check valve control port 18c. As a result, the sixth check valve 18 allows a fluid flow from the high-pressure port 2 via the second valve port 8b and the fourth valve port 8e to the low-pressure port 3 and enables a pressure reduction via this. The fluid flows through the third throttle 17 and is slowed down.This improves controllability of pressure reduction at high pressure port 2 without compromising efficiency during pressure build-up at high pressure port 2.

[0059] Fig. 8 shows a schematic representation of a hydraulic circuit according to an eighth embodiment of the invention.

[0060] The eighth embodiment from Fig. 8 is based on similar features as the first embodiment from Fig. 1 .

[0061] In addition, the check valve system 8 has a first check valve 10. The first check valve is connected to the first valve port 8a at a first check valve port 10a and to the second valve port 8b at a second check valve port 10b. The first check valve 10 is designed to prevent fluid flow from the second check valve port 10b to the first check valve port 10a and to allow fluid flow from the first check valve port 10a to the second check valve port 10b. This allows for efficient pressure buildup at the high-pressure port 2 in a first state, since no further hydraulic elements representing hydraulic resistance are arranged between the first valve port 8a and the second valve port 8b.

[0062] The check valve system 8 has a fourth valve port 8e, a pilot-operated sixth check valve 18, and a third throttle 17. The fourth valve port 8e is fluidly connected to the low-pressure port 3. The sixth check valve 18 is fluidly connected to the fourth valve port 8e at an eleventh check valve port 18a and to the second valve port 8b at a twelfth check valve port 18b. The sixth check valve 18 is configured to prevent fluid flow from the twelfth check valve port 18b to the eleventh check valve port 18a and to permit fluid flow from the eleventh check valve port 18a to the twelfth check valve port 18b. The sixth check valve 18 has a second check valve control port 18c, via which fluid flow from the twelfth check valve port 18b to the eleventh check valve port 18a can be released.The second check valve control port 18c is fluidly connected to the control port 8c.

[0063] In the first state, the fluid flows through the first valve port 8a, the first check valve 10 and the second valve port 8b to the high-pressure port 2 and increases a pressure at the high-pressure port 2. In this case, no fluid flows via the third throttle 17. In the second state, the first check valve 10 prevents a fluid flow from the second valve port 8b to the first valve port 8a. A fluid flows from the first pump outlet 6a via the control port 8c to the second check valve control port 18c. As a result, the sixth check valve 18 allows a fluid flow from the high-pressure port 2 via the second valve port 8b and the fourth valve port 8e to the low-pressure port 3 and enables a pressure reduction via this. In this case, the fluid also flows through the third throttle 17 and is slowed down.This improves controllability of pressure reduction at high pressure port 2 without compromising efficiency during pressure build-up at high pressure port 2.

[0064] Fig. 9 shows a schematic representation of a hydraulic circuit according to a ninth embodiment of the invention.

[0065] The ninth embodiment from Fig. 9 represents an alternative embodiment of the eighth embodiment Fig. 8 The ninth embodiment features an alternative design of the supply unit 4. Instead of the seventh check valve 20 and the eighth check valve 21, the supply unit 4 in the ninth embodiment is designed as a dual-pressure valve 22. This reduces the number of required components in the hydraulic circuit 1 and allows for a more compact design of the hydraulic circuit 1.

[0066] In addition to the above written description of the invention, for its supplementary disclosure, reference is hereby explicitly made to the graphic representation of the invention in the Fig. 1 bis 8 Reference is made. Bezugszeichenliste

[0067] 1 Hydraulic circuit 2 High pressure connection 3 Low pressure connection 4 Supply unit 5 Pump system 6 Pump 6 a First pump connection 6 b Second pump connection 7 Shaft 8 Check valve system 8 a First valve connection 8 b Second valve connection 8 c Control connection 8 d Third valve connection 8 fourth valve connection 9 Pressure equalization line 10 First check valve 10 a First check valve connection 10 b Second check valve connection 10 c First check valve control connection 10 d Displacement 10 e Piston 10 f Check element 11 First throttle 12 Second check valve 12 a Third check valve connection 12 b Fourth check valve connection 13 Third check valve 13 a Fifth check valve connection 13 b Sixth check valve connection 14 Fourth check valve 14 a Eighth check valve connection 14 b Seventh Check valve connection 15 second throttle 16 fifth check valve 16 a lower check valve connection 16 b tenth check valve connection 17 third throttle 18 sixth check valve18aEleventh check valve connection 18bTwelfth check valve connection 18cSecond check valve control connection 19Pressure relief valve 19aFirst pressure relief valve connection 19bSecond pressure relief valve connection 20Seventh check valve 20aThirteenth check valve connection 20bFourteenth check valve connection 21Eighth check valve 21aFifteenth check valve connection 21bSixteenth check valve connection 22Dual pressure valve

Claims

1. Hydraulic circuit (1) comprising • a high-pressure connection (2), • a low-pressure connection (3), • a supply unit (4), and • a pump system (5), • wherein the low-pressure connection (3) is fluidically connected to the high-pressure connection (2) by means of a series connection of the supply unit (4) and the pump system (5), • wherein the pump system (5) has a pump (6) for conveying a fluid, a shaft (7) for driving the pump (6) and at least one releasable check valve system (8), • wherein the pump (6) is configured to convey the fluid from a first pump connection (6a) to a second pump connection (6b) in a first state and to convey the fluid from the second pump connection (6b) to the first pump connection (6a) in a second state,• wherein the check valve system (8) is fluidically connected to the second pump connection (6b) at a first valve connection (8a) and to the high-pressure connection (2) at a second valve connection (8b), • wherein the check valve system (8) is designed to prevent a fluid flow from the second valve connection (8b) to the first valve connection (8a) and to allow a fluid flow from the first valve connection (8a) to the second valve connection (8b), • wherein the check valve system (8) has a control connection (8c) via which a fluid flow from the second valve connection (8b) to the first valve connection (8a) can be released, • wherein the hydraulic circuit (1) is designed to release the fluid flow from the second valve connection (8b) to the first valve connection (8a) via the control connection (8c) when the pump (6) is in the second state,• wherein the supply unit (4) is configured to enable a fluid flow from the low-pressure connection (3) to the first pump connection (6a) in a first state of the pump (6) and to prevent a fluid flow from the second pump connection (6b) to the low-pressure connection (3), • wherein the supply unit (4) is configured to enable a fluid flow from the low-pressure connection (3) to the second pump connection (6b) in a second state of the pump (6) and to prevent a fluid flow from the first pump connection (6a) to the low-pressure connection (3), • wherein o the pump (6) has a leakage flow towards the shaft (7) when conveying the fluid, and the shaft (7) is connected to the low-pressure connection (3) by means of a pressure equalization line (9) in order to discharge the fluid from the shaft (7), and / or o the check valve system (8) has a leakage flow between the control connection (8c) and the first valve connection (8a),when the pump (6) is in the second state., 2. Hydraulic circuit (1) according to claim 1 characterized in that the check valve system (8) has at least a first check valve (10), • wherein the first check valve (10) is connected to the first valve port (8a) at a first check valve port (10a) and to the second valve port (8b) at a second check valve port (10b), and • wherein the first check valve (10) is designed to prevent fluid flow from the second check valve port (10b) to the first check valve port (10a) and to allow fluid flow from the first check valve port (10a) to the second check valve port (10b).

3. Hydraulic circuit (1) according to claim 2 characterized in thatthe first check valve (10) is designed to be releasable, • wherein the first check valve (10) has a first check valve control connection (10c) via which a fluid flow from the second check valve connection (10b) to the first check valve connection (10a) can be released, and • wherein the first check valve control connection (10c) is fluidically connected to the control connection (8c).

4. Hydraulic circuit (1) according to one of claims 2 or 3 characterized in thatthe check valve (10) has a displacement chamber (10d), a piston (10e) and a check element (10f), • wherein the check element (10f) is configured in a third state of the check element (10f) to prevent a fluid flow from the second check valve connection (10b) to the first check valve connection (10a), • wherein the check element (10f) is configured in a fourth state of the check element (10f) to release a fluid flow from the second check valve connection (10b) to the first check valve connection (10a), • wherein the piston (10e) is configured to move in a first direction via the control connection (10c) when pressure builds up in the displacement chamber (10d) and to put the check element (10f) into the fourth state, and • wherein the check valve (10) prevents a leakage flow between the check valve control connection (10c) and the first check valve connection (10a) over the displacement (10d).

5. Hydraulic circuit (1) according to one of the preceding claims characterized in that the check valve system (8) has at least one first throttle (11), • wherein the first throttle (11) is arranged between the first valve connection (8a) and the second valve connection (8b), and • wherein the first check valve (10) and the first throttle (11) are fluidically connected in series with one another.

6. Hydraulic circuit (1) according to one of the preceding claims 2 and 4 characterized in thatthe check valve system (8) has at least a second check valve (12) and a third valve connection (8d), • wherein the third valve connection (8d) is fluidically connected to the second pump connection (6b), • wherein the second check valve (12) is connected to the third valve connection (8d) at a third check valve connection (12a) and to the second valve connection (8b) at a fourth check valve connection (12b), and • wherein the second check valve (12) is designed to prevent fluid flow from the fourth check valve connection (12b) to the third check valve connection (12a) and to allow fluid flow from the third check valve connection (12a) to the fourth check valve connection (12b).

7. Hydraulic circuit (1) according to claim 5 and 6 characterized in thatthe check valve system (8) has a third check valve (13), • wherein the third check valve (13) is fluidically connected to a fifth check valve connection (13a) with the second valve connection (8b) and is fluidically connected to a sixth check valve connection (13b) with the second check valve connection (10b), • wherein the third check valve (13) is designed to prevent fluid flow from the fifth check valve connection (13a) to the sixth check valve connection (13b) and to allow fluid flow from the sixth check valve connection (13b) to the fifth check valve connection (13a), and • wherein the third check valve (13) is arranged fluidically parallel to the first throttle (11).

8. Hydraulic circuit (1) according to claims 3 to 7 characterized in thatthe check valve system (8) comprises a second throttle (15), a fourth check valve (14) and a fifth check valve (16), • wherein the second throttle (15), the fourth check valve (14) and the fifth check valve (16) are fluidically arranged between the first check valve (10) and the first valve connection (8a), • wherein the fourth check valve (14) is fluidically connected to the first check valve connection (10a) at a seventh check valve connection (14b) and to the first valve connection (8a) at an eighth check valve connection (14a), • wherein the fourth check valve (14) is designed to prevent fluid flow from the seventh check valve connection (14b) to the eighth check valve connection (14a) and to allow fluid flow from the eighth check valve connection (14a) to the seventh check valve connection (14b),• wherein the fifth check valve (16) is arranged anti-parallel to the fourth check valve (14), • wherein the fifth check valve (16) is fluidically connected to the first check valve port (10a) at a ninth check valve port (16a) and to the first valve port (8a) at a tenth check valve port (16b), • wherein the fifth check valve (16) is designed to prevent fluid flow from the tenth check valve port (16b) to the ninth check valve port (16a) and to allow fluid flow from the ninth check valve port (16a) to the tenth check valve port (16b), and • wherein the second throttle (15) is fluidically arranged between the tenth check valve port (16b) and the second valve port (8b) and parallel to the fourth check valve (14).

9. Hydraulic circuit (1) according to claim 2 characterized in thatthe check valve system (8) has a fourth valve port (8e), a pilot-operated sixth check valve (18) and a third throttle (17), • wherein the fourth valve port (8e) is fluidically connected to the low-pressure port (3), • wherein the sixth check valve (18) is fluidically connected to the fourth valve port (8e) by an eleventh check valve port (18a) and to the second valve port (8b) by a twelfth check valve port (18b), and • wherein the sixth check valve (18) is designed to prevent fluid flow from the twelfth check valve port (18b) to the eleventh check valve port (18a) and to allow fluid flow from the eleventh check valve port (18a) to the twelfth check valve port (18b), • wherein the sixth check valve (18) has a second check valve control port (18c),via which a fluid flow from the twelfth check valve connection (18b) to the eleventh check valve connection (18a) can be released, and • wherein the second check valve control connection (18c) is fluidically connected to the control connection (8c)., 10. Hydraulic circuit (1) according to one of the preceding claims characterized by a pressure relief valve (19), wherein the pressure relief valve (19) is connected to the high-pressure port (2) at a first pressure relief valve port (19a) and to the low-pressure port (3) at a second pressure relief valve port (19b), wherein the pressure relief valve (19) is connected to the high-pressure port (2) and the low-pressure port (3) in parallel to the pump system (5) and to the supply unit.

11. Hydraulic circuit (1) according to one of the preceding claims characterized in thatthe supply unit has a seventh check valve (20) and an eighth check valve, • wherein the seventh check valve (20) is connected to the low-pressure port (3) at a thirteenth check valve port (20a) and to the first pump port (6a) at a fourteenth check valve port (20b) • wherein the seventh check valve (20) is designed to prevent fluid flow from the fourteenth check valve port (20b) to the thirteenth check valve port (20a) and to allow fluid flow from the thirteenth check valve port (20a) to the fourteenth check valve port (20b) • wherein the eighth check valve (21) is connected to the low-pressure port (3) at a fifteenth check valve port (16b) and to the second pump port (6b) at a sixteenth check valve port (16b) • wherein the eighth check valve (21) is designed Fluid flow from the sixteenthCheck valve port (16b) to prevent the fifteenth check valve port (16b) and to allow fluid flow from the fifteenth check valve port (16b) to the sixteenth check valve port (16b).

12. Hydraulic circuit (1) according to one of the preceding claims characterized in that the supply unit (4) is designed as a two-pressure valve (22)

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