Closed hydraulic system, vehicle and control method of closed hydraulic system

Abstract

The invention relates to the technical field of vehicles, and particularly discloses a closed hydraulic system, a vehicle and a control method of the closed hydraulic system.The closed hydraulic system comprises an oil supplementing pump, a hydraulic oil cylinder, a first closed pump and a balance valve, the input end of the oil supplementing pump is connected with an oil tank, the output end of the oil supplementing pump is connected with an oil supplementing path, and the hydraulic oil cylinder is provided with a rod cavity and a rodless cavity; one end of the first closed pump is connected with the rodless cavity through a first oil way, and the other end of the first closed pump is connected with the rod cavity through a second oil way, so that a hydraulic loop is formed between the first closed pump and the hydraulic oil cylinder, and the first closed pump can rotate forwards and reversely; the balance valve can enable one of the first oil way and the second oil way with smaller oil pressure to be communicated with the oil supplementing way, so that the flow difference between the rod cavity and the rodless cavity can be compensated, oil liquid with lower temperature in the oil supplementing way can be replaced with oil liquid with higher temperature in the first oil way or the second oil way, the heat balance of the system is optimized, and the service life of the system is prolonged. Temperature monitoring is not needed, and normal operation of the hydraulic oil cylinder is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicles, and in particular to a closed hydraulic system, a vehicle and a control method of the closed hydraulic system. Background Art

[0002] Single-rod double-acting piston hydraulic cylinders are widely used in various mechanical equipment to drive the movement of the mechanism by controlling the extension and retraction direction and speed of the hydraulic cylinder's piston rod.

[0003] In the prior art, a closed hydraulic system is disclosed in a previous patent with application number CN202110530288.3, ​​specifically a closed electro-hydraulic control system for a mechanical arm with an asymmetric cylinder. The rod chamber and the rodless chamber of the hydraulic cylinder are connected by an oil pump to realize the flow of oil in the two chambers. At the same time, an accumulator is also configured to compensate for the flow difference between the rod chamber and the rodless chamber and recover part of the energy, so as to realize the decoupling of the oil cylinder. However, in this system, the accumulator will overflow at high pressure when the maximum pressure is reached, and the pipeline connected to the rod chamber and the rodless chamber will also overflow at high pressure when the maximum pressure is reached, which will cause power loss and generate a lot of heat to affect the thermal balance of the system. In order to avoid the oil temperature in the system from being too high, temperature monitoring is also required. When the temperature is abnormal, the hot oil in the system needs to overflow to the oil tank through the low-pressure overflow valve, and the oil in the oil tank is replenished into the system, affecting the normal operation of the oil cylinder. Summary of the invention

[0004] The object of the present invention is to provide a closed hydraulic system, a vehicle and a control method for the closed hydraulic system, so as to optimize the thermal balance of the existing closed hydraulic system.

[0005] On the one hand, the present invention provides a closed hydraulic system, which includes an oil replenishment pump, a hydraulic cylinder and a first closed pump, the input end of the oil replenishment pump is connected to the oil tank, the output end of the oil replenishment pump is connected to the oil replenishment oil circuit, the hydraulic cylinder has a rod chamber and a rodless chamber, one end of the first closed pump is connected to the first oil circuit, the first oil circuit is connected to the rodless chamber, the other end of the first closed pump is connected to the second oil circuit, the second oil circuit is connected to the rod chamber, and the first closed pump can rotate forward and reverse; the closed hydraulic system also includes a balancing valve, which is configured to connect the one with smaller oil pressure between the first oil circuit and the second oil circuit to the oil replenishment oil circuit.

[0006] As a preferred technical solution of the closed hydraulic system, the closed hydraulic system also includes:

[0007] a second closed pump, the second closed pump can rotate forward and reverse, one end of the second closed pump is connected to the oil replenishment circuit, and the other end is connected to the third oil circuit, and the third oil circuit is in communication with the first oil circuit;

[0008] The first reversing valve is arranged in the third oil circuit, and the first reversing valve is used to control the connection and disconnection of the third oil circuit.

[0009] As a preferred technical solution for the closed hydraulic system, the closed hydraulic system also includes a motor and a battery electrically connected to the motor. The motor is simultaneously transmission-connected to the first closed pump and the second closed pump, and the motor can simultaneously drive the first closed pump and the second closed pump to rotate. When the first closed pump pumps oil into the first oil circuit, the second closed pump pumps oil into the third oil circuit.

[0010] As a preferred technical solution of the closed hydraulic system, the closed hydraulic system also includes:

[0011] a first bypass oil circuit, wherein two ends of the first bypass oil circuit are respectively connected to the oil replenishment oil circuit and the third oil circuit, and a connection point between the first bypass oil circuit and the third oil circuit is located between the second closed pump and the first reversing valve;

[0012] The second reversing valve is arranged in the first bypass oil circuit, and the second reversing valve is used to control the connection and disconnection of the first bypass oil circuit.

[0013] As a preferred technical solution of the closed hydraulic system, the closed hydraulic system also includes:

[0014] a second bypass oil circuit, wherein two ends of the second bypass oil circuit are respectively connected to the oil replenishment oil circuit and the third oil circuit, and a connection point between the second bypass oil circuit and the third oil circuit is located between the second closed pump and the first reversing valve;

[0015] A one-way valve is provided in the second bypass oil passage, and the one-way valve is configured to only allow oil to flow from the oil replenishment oil passage through the second bypass oil passage to the third oil passage.

[0016] As a preferred technical solution for the closed hydraulic system, the closed hydraulic system also includes a regeneration oil circuit connected between the first oil circuit and the second oil circuit, and a regeneration valve arranged in the regeneration oil circuit, and the regeneration valve is used to control the connection and disconnection of the regeneration oil circuit.

[0017] As a preferred technical solution of the closed hydraulic system, the closed hydraulic system further includes a first overflow valve connected between the oil replenishment circuit and the first oil circuit, the first overflow valve being configured to enable the oil in the first oil circuit to overflow to the oil replenishment circuit when the oil exceeds a first set pressure;

[0018] The closed hydraulic system further includes a second relief valve connected between the oil replenishment circuit and the second oil circuit, wherein the second relief valve is configured to allow the oil in the second oil circuit to overflow to the oil replenishment circuit when the oil pressure exceeds a second set pressure.

[0019] As a preferred technical solution for the closed hydraulic system, the closed hydraulic system also includes an oil replenishment overflow valve connected between the oil replenishment circuit and the oil tank, and the oil replenishment overflow valve is configured to allow the oil in the oil replenishment circuit to overflow to the oil tank when the oil exceeds a third set pressure.

[0020] As an optimal technical solution for a closed hydraulic system, the balancing valve includes a first interface, a second interface and a third interface, the first interface is connected to the first oil circuit, the second interface is connected to the second oil circuit, and the third interface is connected to the oil replenishment circuit. When the oil pressure of the first oil circuit is greater than the oil pressure of the second oil circuit, the balancing valve connects the second interface and the third interface, and the first interface is disconnected; when the oil pressure of the first oil circuit is less than the oil pressure of the second oil circuit, the balancing valve connects the first interface and the third interface, and the second interface is disconnected.

[0021] On the other hand, the present invention further provides a vehicle, comprising the closed hydraulic system described in any one of the above schemes, wherein the hydraulic cylinder is a boom cylinder, a dipper arm cylinder or a bucket cylinder.

[0022] On the other hand, the present invention provides a control method for a closed hydraulic system, which is implemented by the closed hydraulic system in any of the above schemes, wherein the closed hydraulic system also includes a second closed pump and a motor, wherein the second closed pump can rotate forward and reverse, one end of the second closed pump is connected to an oil replenishment circuit, and the other end is connected to a third oil circuit, wherein the third oil circuit is connected to the first oil circuit; the motor is simultaneously connected to the first closed pump and the second closed pump in a transmission manner, and the motor can simultaneously drive the first closed pump and the second closed pump to rotate; the control method for the closed hydraulic system includes:

[0023] Get the position of the joystick;

[0024] Determining the extension and retraction requirements of the piston rod of the hydraulic cylinder based on the position of the operating handle;

[0025] Obtaining a high-pressure oil chamber of a hydraulic oil cylinder, wherein the high-pressure oil chamber of the hydraulic oil cylinder is the one with a larger oil pressure between a rod chamber and a rodless chamber of the hydraulic oil cylinder oil;

[0026] Obtaining the correspondence between the extension and retraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder and the working quadrant of the closed hydraulic system, wherein the working quadrant of the closed hydraulic system includes the first quadrant, the second quadrant, the third quadrant and the fourth quadrant;

[0027] Determining the working quadrant of the closed hydraulic system based on the expansion and contraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder and the corresponding relationship;

[0028] Determine whether the working quadrant of the closed hydraulic system is the third quadrant or the fourth quadrant;

[0029] If so, the speed of the motor is determined based on the operating quadrant.

[0030] As a preferred technical solution of the control method of the closed hydraulic system, when judging whether the working quadrant of the closed hydraulic system is the third quadrant or the fourth quadrant, if not, the control method of the closed hydraulic system further includes:

[0031] Determining a required speed of the motor based on the position of the joystick;

[0032] determining a required flow rate of the oil pump based on the required speed;

[0033] obtaining the maximum oil pressure of the oil pressure in the rod chamber and the oil pressure in the rodless chamber;

[0034] determining a required power of the oil pump based on the required flow rate and the maximum oil pressure;

[0035] Get the rated power of the motor;

[0036] Determine the required power of the oil pump and half of the rated power of the motor;

[0037] If the required power of the oil pump is greater than or equal to half of the rated power of the motor, only the first closed pump is turned on; if the required power of the oil pump is less than half of the rated power of the motor, the first closed pump and the second closed pump are turned on at the same time.

[0038] As a preferred technical solution of the control method of the closed hydraulic system, when only the first closed pump is turned on, when the first closed pump and the second closed pump are turned on at the same time, the control method of the closed hydraulic system further includes:

[0039] Determine whether the working quadrant of the closed hydraulic system is the second quadrant;

[0040] If not, the speed of the motor is determined based on the operating quadrant.

[0041] As a preferred technical solution of the control method of the closed hydraulic system, the closed hydraulic system further includes a battery electrically connected to the motor;

[0042] When determining whether the working quadrant of the closed hydraulic system is the second quadrant, if so, the control method of the closed hydraulic system further includes:

[0043] determining whether the opening of the joystick exceeds a set opening based on the position of the joystick;

[0044] If so, the motor generates electricity and stores it in the battery; if not, the speed of the motor is determined based on the working quadrant.

[0045] The beneficial effects of the present invention are as follows:

[0046] The invention provides a closed hydraulic system, a vehicle and a control method for the closed hydraulic system, wherein the closed hydraulic system comprises an oil replenishment pump, a hydraulic oil cylinder, a first closed pump and a balancing valve, wherein the input end of the oil replenishment pump is connected to the oil tank, the output end of the oil replenishment pump is connected to the oil replenishment oil circuit, the hydraulic oil cylinder has a rod chamber and a rodless chamber, one end of the first closed pump is connected to the first oil circuit, the first oil circuit is connected to the rodless chamber, the other end of the first closed pump is connected to the second oil circuit, the second oil circuit is connected to the rod chamber, and the first closed pump can rotate forward and reverse; the balancing valve is configured to make the first The oil circuit and the second oil circuit, the one with the smaller oil pressure is connected to the oil replenishment circuit, the first closed pump forms a hydraulic circuit with two chambers of the hydraulic cylinder through the first oil circuit and the second oil circuit, and the oil replenishment circuit is connected with the one with the smaller oil pressure between the first oil circuit and the second oil circuit through a balancing valve, which can make up for the difference in flow rate between the rod chamber and the rodless chamber, and the lower temperature oil in the oil replenishment circuit can be replaced with the higher temperature oil in the hydraulic circuit, thereby optimizing the thermal balance of the system. There is no need to set temperature monitoring, and the normal operation of the hydraulic cylinder can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of a closed hydraulic system in an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of the working quadrant of a closed hydraulic system in an embodiment of the present invention;

[0049] Figure 3 A first flow chart of a control method for a closed hydraulic system in an embodiment of the present invention;

[0050] Figure 4 This is a second flow chart of the control method of the closed hydraulic system in an embodiment of the present invention.

[0051] In the figure:

[0052] 1. Hydraulic cylinder; 101. Rod chamber; 102. Rodless chamber;

[0053] 2. Oil replenishment pump; 3. First closed pump; 4. Balance valve; 5. Oil tank; 6. Oil replenishment circuit; 7. First oil circuit; 8. Second oil circuit; 9. Second closed pump; 10. Third oil circuit; 11. First reversing valve; 12. First bypass oil circuit; 13. Second reversing valve; 14. Second bypass oil circuit; 15. Check valve; 16. Motor; 17. Regeneration oil circuit; 18. Regeneration valve; 19. First overflow valve; 20. Second overflow valve; 21. Oil replenishment overflow valve; 22. Oil replenishment motor. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0056] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0058] The existing closed electro-hydraulic control system of the asymmetric cylinder robot arm connects the rod chamber and the rodless chamber of the hydraulic cylinder through an oil pump to realize the flow of oil in the two chambers. At the same time, an accumulator is also configured to compensate for the flow difference between the rod chamber and the rodless chamber and recover part of the energy, which can realize the decoupling of the oil cylinder. However, in this system, the accumulator will overflow at high pressure when the maximum pressure is reached, and the pipeline connected to the rod chamber and the rodless chamber will also overflow at high pressure when the maximum pressure is reached. This will cause power loss and generate a lot of heat to affect the thermal balance of the system. In order to avoid the oil temperature in the system from being too high, additional temperature monitoring is required. When the temperature is abnormal, the hot oil in the system needs to overflow to the oil tank through the low-pressure overflow valve, and the oil in the oil tank is replenished to the system, affecting the normal operation of the oil cylinder.

[0059] In this regard, this embodiment provides a closed hydraulic system to solve the above problems.

[0060] like Figure 1 As shown, the closed hydraulic system includes an oil replenishment pump 2, a hydraulic cylinder 1, a first closed pump 3 and a balance valve 4. The input end of the oil replenishment pump 2 is connected to the oil tank 5, the output end of the oil replenishment pump 2 is connected to the oil replenishment oil circuit 6, the hydraulic cylinder 1 has a rod chamber 101 and a rodless chamber 102, one end of the first closed pump 3 is connected to the first oil circuit 7, the first oil circuit 7 is connected to the rodless chamber 102, the other end of the first closed pump 3 is connected to the second oil circuit 8, the second oil circuit 8 is connected to the rod chamber 101, and the first closed pump 3 can rotate forward and reverse; the balance valve 4 is configured so that the one with a smaller oil pressure between the first oil circuit 7 and the second oil circuit 8 is connected to the oil replenishment oil circuit 6.

[0061] The closed hydraulic system provided in this embodiment has a first closed pump 3 that forms a hydraulic circuit with two chambers of the hydraulic cylinder 1 through the first oil circuit 7 and the second oil circuit 8. When the first closed pump 3 rotates forward, the oil in the rod chamber 101 can be transported to the rodless chamber 102 to extend the piston rod of the hydraulic cylinder 1. When the first closed pump 3 rotates reversely, the oil in the rodless chamber 102 can be transported to the rod chamber 101 to retract the piston rod of the hydraulic cylinder 1. Since there is a difference in cross-sectional area between the rod chamber 101 and the rodless chamber 102, there is a flow difference between the rod chamber 101 and the rodless chamber 102. The balance valve 4 connects the oil replenishing circuit 6 and the smaller oil pressure between the first oil circuit 7 and the second oil circuit 8, which can compensate for the above flow difference, and the oil in the oil replenishing circuit 6 can be replaced with the oil in the hydraulic circuit. The oil temperature in the oil replenishing circuit 6 is relatively low. When the oil temperature in the hydraulic circuit is too high, the oil temperature in the hydraulic circuit can be effectively reduced, thereby ensuring the normal oil temperature in the hydraulic circuit, optimizing the thermal balance of the system, and eliminating the need to set temperature monitoring. The normal operation of the hydraulic cylinder 1 can be guaranteed.

[0062] It should be noted that the oil replenishing pump 2 can be driven by the oil replenishing motor 22. The number of hydraulic cylinders 1 can be one or more. When the number of hydraulic cylinders 1 is more than one, the rodless chambers 102 of the plurality of hydraulic cylinders 1 are all connected to the first oil circuit 7, and the rod chambers 101 of the plurality of hydraulic cylinders 1 are all connected to the second oil circuit 8. Specifically, the present embodiment exemplarily provides a solution in which the number of hydraulic cylinders 1 is two.

[0063] Optionally, the closed hydraulic system further includes a first overflow valve 19 connected between the oil replenishing circuit 6 and the first oil circuit 7, and the first overflow valve 19 is configured to allow the oil in the first oil circuit 7 to overflow to the oil replenishing circuit 6 when the oil exceeds the first set pressure. By setting the first overflow valve 19, it is possible to prevent the pressure of the oil in the first oil circuit 7 and the rodless chamber 102 from exceeding the first set pressure. The first set pressure can be set according to actual needs.

[0064] Optionally, the closed hydraulic system further includes a second overflow valve 20 connected between the oil replenishing circuit 6 and the second oil circuit 8, and the second overflow valve 20 is configured to enable the oil in the second oil circuit 8 to overflow to the oil replenishing circuit 6 when the oil exceeds the second set pressure. By setting the second overflow valve 20, it is possible to prevent the pressure of the oil in the second oil circuit 8 and the rod chamber 101 from exceeding the second set pressure. The second set pressure can be set according to actual needs.

[0065] Optionally, the closed hydraulic system further includes an oil replenishment overflow valve 21 connected between the oil replenishment oil circuit 6 and the oil tank 5, and the oil replenishment overflow valve 21 is configured to allow the oil in the oil replenishment oil circuit 6 to overflow to the oil tank 5 when the oil exceeds a third set pressure. The oil replenishment pressure of the oil replenishment oil circuit 6 can be limited by setting the oil replenishment overflow valve 21. The third set pressure can be set according to actual needs.

[0066] Optionally, the closed hydraulic system further includes a second closed pump 9 and a first reversing valve 11. The second closed pump 9 can rotate forward and reverse, one end of the second closed pump 9 is connected to the oil replenishment circuit 6, and the other end is connected to the third oil circuit 10, and the third oil circuit 10 is connected to the first oil circuit 7; the first reversing valve 11 is arranged in the third oil circuit 10, and the first reversing valve 11 is used to control the connection and disconnection of the third oil circuit 10. Specifically, when the first reversing valve 11 is connected to the third oil circuit 10, a part of the oil in the rodless chamber 102 can be pumped to the rod chamber 101 through the first closed pump 3, and another part of the oil in the rodless chamber 102 can be pumped to the oil replenishing circuit 6 through the second closed pump 9; or, the oil in the rod chamber 101 can be pumped to the rodless chamber 102 through the first closed pump 3, and the oil in the oil replenishing circuit 6 can be pumped to the rodless chamber 102 through the second closed pump 9, so as to improve the extension and retraction efficiency of the piston rod of the hydraulic cylinder 1, and can further compensate for the flow difference between the rod chamber 101 and the rodless chamber 102.

[0067] It should be noted that when the first reversing valve 11 disconnects the third oil circuit 10, the oil is driven to flow between the rod chamber 101 and the rodless chamber 102 only through the first closed pump 3. In this embodiment, the first reversing valve 11 is specifically a two-position two-way valve. Both the first closed pump 3 and the second closed pump 9 are quantitative pumps.

[0068] Optionally, the closed hydraulic system further includes a motor 16, and a battery (not shown in the attached drawings) electrically connected to the motor 16, the motor 16 is simultaneously connected to the first closed pump 3 and the second closed pump 9 in a transmission manner, and the motor 16 can simultaneously drive the first closed pump 3 and the second closed pump 9 to rotate, and when the first closed pump 3 pumps oil to the first oil circuit 7, the second closed pump 9 pumps oil to the third oil circuit 10. Specifically, the battery supplies electric energy to the motor 16, and the motor 16 can actively drive the first closed pump 3 and the second closed pump 9 to rotate forward or reverse at the same time. It should be noted that when the first closed pump 3 and the second closed pump 9 reverse at the same time, they may not be driven by the motor 16, but may be driven by oil. Specifically, if the piston rod of the hydraulic cylinder 1 retracts rapidly by relying on the deadweight of the external component, the oil can drive the first closed pump 3 and the second closed pump 9 to reverse and drive the motor 16 to reverse, thereby prompting the motor 16 to generate electricity and store it in the battery, realizing the recycling of system energy, reducing the heating power of the system, and improving the system efficiency.

[0069] In other embodiments, the first closed-type pump 3 and the second closed-type pump 9 may also be driven by an internal combustion engine.

[0070] Optionally, the closed hydraulic system further includes a first bypass oil circuit 12 and a second reversing valve 13, the two ends of the first bypass oil circuit 12 are respectively connected to the oil replenishment oil circuit 6 and the third oil circuit 10, and the connection between the first bypass oil circuit 12 and the third oil circuit 10 is located between the second closed pump 9 and the first reversing valve 11; the second reversing valve 13 is arranged in the first bypass oil circuit 12, and the second reversing valve 13 is used to control the connection and disconnection of the first bypass oil circuit 12. When the second reversing valve 13 is connected to the first bypass oil circuit 12, the inlet and outlet pressures of the second closed pump 9 are the same, the second closed pump 9 is self-circulated through the first bypass oil circuit 12, and does not work externally, only the first closed pump 3 works externally, which can reduce energy loss; when the second reversing valve 13 disconnects the first bypass oil circuit 12 and the first reversing valve 11 is connected to the third oil circuit 10, the second closed pump 9 and the first closed pump 3 work together. Specifically, the second reversing valve 13 in this embodiment is a two-position two-way valve.

[0071] Optionally, the closed hydraulic system further includes a second bypass oil circuit 14 and a one-way valve 15. The two ends of the second bypass oil circuit 14 are respectively connected to the oil replenishment oil circuit 6 and the third oil circuit 10, and the connection between the second bypass oil circuit 14 and the third oil circuit 10 is located between the second closed pump 9 and the first reversing valve 11; the one-way valve 15 is arranged in the second bypass oil circuit 14, and the one-way valve 15 is configured to only allow the oil to flow from the oil replenishment oil circuit 6 to the third oil circuit 10 through the second bypass oil circuit 14. In this arrangement, when the second reversing valve 13 disconnects the first bypass oil circuit 12, and the first reversing valve 11 disconnects the third oil circuit 10, and the first closed pump 3 and the second closed pump 9 are reversed, the inlet and outlet pressures of the second closed pump 9 are the same, and the second closed pump 9 can self-circulate through the second bypass oil circuit 14, and also does not perform work externally, so as to reduce energy loss.

[0072] Optionally, the closed hydraulic system further includes a regeneration oil circuit 17 connected between the first oil circuit 7 and the second oil circuit 8, and a regeneration valve 18 disposed in the regeneration oil circuit 17, and the regeneration valve 18 is used to control the connection and disconnection of the regeneration oil circuit 17. When the regeneration valve 18 connects the regeneration oil circuit 17, the regeneration oil circuit 17 connects the first oil circuit 7 and the second oil circuit 8. At this time, the oil in the rodless chamber 102 can flow directly into the rod chamber 101 through the regeneration valve 18 without passing through the first closed pump 3 and the second closed pump 9, so that the piston rod of the hydraulic cylinder 1 can have the fastest movement speed.

[0073] Optionally, the balancing valve 4 includes a first interface, a second interface and a third interface, the first interface is connected to the first oil circuit 7, the second interface is connected to the second oil circuit 8, and the third interface is connected to the oil replenishment circuit 6. When the oil pressure of the first oil circuit 7 is greater than the oil pressure of the second oil circuit 8, the balancing valve 4 connects the second interface with the third interface, and the first interface is disconnected; when the oil pressure of the first oil circuit 7 is less than the oil pressure of the second oil circuit 8, the balancing valve 4 connects the first interface with the third interface, and the second interface is disconnected. Preferably, when the oil pressure of the first oil circuit 7 is equal to the oil pressure of the second oil circuit 8, the first interface, the second interface and the third interface are all disconnected, at which time the pressure of the oil in the rod chamber 101 and the rodless chamber 102 of the hydraulic cylinder 1 can be ensured to be stable, thereby ensuring the stability of the position of the piston rod.

[0074] Specifically, in this embodiment, the balancing valve 4 is a three-position three-way valve. The balancing valve 4 has a left position, a right position and a middle position. When the balancing valve 4 is in the left position, the first interface and the third interface are connected, and the second interface is disconnected. When the balancing valve 4 is in the right position, the second interface and the third interface are connected, and the first interface is disconnected. When the balancing valve 4 is in the middle position, the first interface, the second interface and the third interface are all disconnected.

[0075] It should be noted that the movement direction of the piston rod of the hydraulic cylinder 1 and the direction of the load force on the piston rod of the hydraulic cylinder 1 jointly determine the oil pressure in the rodless chamber 102 and the rod chamber 101. When the direction of the load force is consistent with the movement direction of the piston rod of the hydraulic cylinder 1, the load force is a negative load. When the direction of the load force is opposite to the movement direction of the piston rod of the hydraulic cylinder 1, the load force is a positive load. Specifically: (1) When the piston rod of the hydraulic cylinder 1 retracts inward, when the piston rod of the hydraulic cylinder 1 is subjected to a negative load, the oil pressure in the rodless chamber 102 is greater than the oil pressure in the rod chamber 101, and the balance valve 4 connects the oil replenishing circuit 6 and the second oil circuit 8; when the piston rod of the hydraulic cylinder 1 is subjected to a positive load, the oil pressure in the rod chamber 101 is greater than the oil pressure in the rodless chamber 102, and the balance valve 4 connects the oil replenishing circuit 6 and the first oil circuit 7; (2) When the piston rod of the hydraulic cylinder 1 extends outward, when the piston rod of the hydraulic cylinder 1 is subjected to a negative load, the oil pressure in the rodless chamber 102 is less than the oil pressure in the rod chamber 101, and the balance valve 4 connects the oil replenishing circuit 6 and the first oil circuit 7; when the piston rod of the hydraulic cylinder 1 is subjected to a positive load, the oil pressure in the rod chamber 101 is less than the oil pressure in the rodless chamber 102, and the balance valve 4 connects the oil replenishing circuit 6 and the second oil circuit 8.

[0076] In this embodiment, the balancing valve 4 is specifically a hydraulically controlled valve, and the balancing valve 4 has a first hydraulic control end and a second hydraulic control end, the first hydraulic control end is connected to the first oil circuit 7, and the second hydraulic control end is connected to the second oil circuit 8. The first hydraulic control end and the second hydraulic control end are respectively located on both sides of the valve core of the balancing valve 4, and the oil of the first hydraulic control end and the second hydraulic control end directly acts on the valve core of the balancing valve 4. The force of the oil of the first hydraulic control end acting on the valve core of the balancing valve 4 and the force of the oil of the second hydraulic control end acting on the valve core of the balancing valve 4 are compared to determine the stop position of the valve core of the balancing valve 4. Specifically, when the oil pressure of the first hydraulic control end is less than the oil pressure of the second hydraulic control end, the balancing valve 4 is located in the left position; when the oil pressure of the first hydraulic control end is greater than the oil pressure of the second hydraulic control end, the balancing valve 4 is located in the right position; when the oil pressure of the first hydraulic control end is equal to the oil pressure of the second hydraulic control end, the balancing valve 4 is located in the middle position. In other embodiments, the balancing valve 4 can also be an electrically controlled valve.

[0077] Optionally, in the present application, each valve and oil pump may be integrated on the motor 16, which can reduce the complexity of the system and the complexity of the control, and reduce the space occupied by the structure.

[0078] This embodiment also provides a vehicle, including the above-mentioned closed hydraulic system. The vehicle can be an excavator, a loader, etc. Taking an excavator as an example, the hydraulic cylinder 1 can be a boom cylinder, a bucket cylinder or a dipper rod cylinder of the excavator.

[0079] This embodiment also provides a control method for a closed hydraulic system. The control method for the closed hydraulic system is implemented by the closed hydraulic system. Figure 2 and Figure 3 , the control method of the closed hydraulic system comprises the following steps:

[0080] S100: Acquire the position of the joystick.

[0081] The position of the operating handle can be detected by a position sensor disposed on the operating handle. The operating handle is used to control the speed and rotation direction of the motor 16, thereby controlling the telescopic direction and movement speed of the piston rod of the hydraulic oil cylinder 1.

[0082] S200: Determine the extension and retraction requirement of the piston rod of the hydraulic cylinder 1 based on the position of the operating handle.

[0083] The controller may pre-store a first mapping relationship between the position of the joystick and the extension and retraction requirements of the piston rod of the hydraulic cylinder 1, and the extension and retraction requirements of the piston rod may be determined according to the position of the joystick and the first mapping relationship. The extension and retraction requirements of the piston rod include the extension requirements of the piston rod and the retraction requirements of the piston rod. The first mapping relationship may be obtained through a large number of experiments in the early stage.

[0084] S300: Acquire the high-pressure oil chamber of hydraulic cylinder 1.

[0085] The high-pressure oil chamber of the hydraulic cylinder 1 is the one with the larger oil pressure between the rod chamber 101 and the rodless chamber 102 of the hydraulic cylinder 1. Specifically, the oil pressure in the rod chamber 101 and the rodless chamber 102 can be detected by the oil pressure sensor, and the chamber corresponding to the larger oil pressure is the high-pressure oil chamber of the hydraulic cylinder 1.

[0086] S400: Obtaining the correspondence between the extension and retraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic oil cylinder 1 and the working quadrant of the closed hydraulic system.

[0087] The corresponding relationship between the expansion and contraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder 1 and the working quadrant of the closed hydraulic system can be obtained through a large number of previous experiments and pre-stored in the controller.

[0088] Among them, the working quadrant is a constant power curve distribution diagram of the closed hydraulic system, the horizontal axis is flow, and the vertical axis is pressure. The working quadrant of the closed hydraulic system includes the first quadrant, the second quadrant, the third quadrant and the fourth quadrant, and each quadrant corresponds to different expansion and contraction requirements of the piston rod and the high-pressure oil chamber of the hydraulic cylinder 1. Therefore, the working quadrant of the closed hydraulic system can be determined from the above correspondence through the expansion and contraction requirements of the piston rod and the high-pressure oil chamber of the hydraulic cylinder 1.

[0089] It is understandable that, since the load on the piston rod may be a negative load or a positive load, when the piston rod is extended, the oil pressure in the rodless chamber 102 may be larger, or the oil pressure in the rod chamber 101 may be larger; when the piston rod is retracted, the oil pressure in the rodless chamber 102 may be larger, or the oil pressure in the rod chamber 101 may be larger. Based on this, if Figure 2 As shown, when the piston rod is extended, if the oil pressure in the rodless chamber 102 is large, the closed hydraulic system is in the first quadrant, and if the oil pressure in the rod chamber 101 is large, the closed hydraulic system is in the fourth quadrant; when the piston rod is retracted, if the oil pressure in the rodless chamber 102 is large, the closed hydraulic system is in the second quadrant, and if the oil pressure in the rod chamber 101 is large, the closed hydraulic system is in the third quadrant.

[0090] S500: Determine the working quadrant of the closed hydraulic system based on the extension and retraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder 1 and the corresponding relationship.

[0091] S600: Determine whether the working quadrant of the closed hydraulic system is the third quadrant or the fourth quadrant.

[0092] If yes, execute S700.

[0093] S700: Determine the rotation speed of the motor 16 based on the working quadrant.

[0094] In this embodiment, when the working quadrant of the closed hydraulic system is in the third quadrant or the fourth quadrant, there is only one working state of the closed hydraulic system. Specifically, when the working quadrant of the closed hydraulic system is in the third quadrant or the fourth quadrant, only the first closed pump 3 is turned on and the second closed pump 9 is turned off. Specifically, the third oil circuit 10 can be closed by the first reversing valve 11 to achieve that the second closed pump 9 does not participate in the output.

[0095] Therefore, when the working quadrant of the closed hydraulic system is in the third quadrant or the fourth quadrant, the first closed pump 3 can be directly involved in the output, and the second closed pump 9 does not participate in the output. At this time, it is only necessary to determine the speed of the motor 16 according to the working quadrant to achieve rapid adjustment of the closed hydraulic system.

[0096] Specifically, the controller pre-stores a second mapping relationship between the working quadrant and the speed of the motor 16. The speed of the motor 16 can be determined by the working quadrant of the hydraulic system and the second mapping relationship, and the motor 16 outputs the speed, thereby realizing rapid adjustment of the closed hydraulic system. The second mapping relationship can be obtained through a large number of experiments in the early stage.

[0097] Optionally, when executing S600, if not, execute S800.

[0098] S800: Determine the required speed of the motor 16 based on the position of the joystick.

[0099] The controller pre-stores a third mapping relationship between the position of the joystick and the required speed of the motor 16. The required speed of the motor 16 can be determined according to the position of the joystick and the third mapping relationship, and the third mapping relationship can be obtained through a large number of previous experiments.

[0100] S900: Determine a required flow rate of the oil pump based on the required speed.

[0101] The controller pre-stores a fourth mapping relationship between the required speed and the required flow rate of the oil pump, and the required flow rate of the oil pump can be determined according to the required speed and the fourth mapping relationship. The fourth mapping relationship can be obtained through a large number of experiments in the early stage.

[0102] It should be noted that the required flow rate of the oil pump corresponds to the total required flow rate of the first closed pump 3 and the second closed pump 9. In this embodiment, the first closed pump 3 and the second closed pump 9 are both fixed displacement pumps, and the fourth mapping relationship is specifically that the required flow rate of the oil pump is equal to the product of the sum of the displacements of the first closed pump 3 and the second closed pump 9 and the required speed.

[0103] S1000 : Acquire the maximum oil pressure of the oil pressure in the rod chamber 101 and the oil pressure in the rodless chamber 102 .

[0104] S1100: Determine the required power of the oil pump based on the required flow rate and the maximum oil pressure.

[0105] The controller pre-stores a fifth mapping relationship between the required flow rate, the maximum oil pressure and the required power of the oil pump. The required power of the oil pump can be determined according to the required flow rate, the maximum oil pressure and the fifth mapping relationship, and the fifth mapping relationship can be obtained through a large number of experiments in the early stage.

[0106] S1200: Acquire the rated power of the motor 16.

[0107] The rated power of the motor 16 is related to the model of the motor 16 and is pre-stored in the controller.

[0108] S1300: Determine whether the required power of the oil pump is not less than half of the rated power of the motor 16.

[0109] If yes, execute S1400; if no, execute S1500.

[0110] S1400: Only the first closed pump 3 is turned on, and the process returns to S700.

[0111] S1500: The first closed pump 3 and the second closed pump 9 are turned on simultaneously.

[0112] Specifically, when the working quadrant of the closed hydraulic system is in the first quadrant or the second quadrant, there are two corresponding working states of the closed hydraulic system, one of which is that only the first closed pump 3 participates in the output, and the second closed pump 9 does not participate in the output; the other is that both the first closed pump 3 and the second closed pump 9 participate in the output. Therefore, when it is determined that the working quadrant of the closed hydraulic system is in the first quadrant or the second quadrant, it is necessary to further determine whether the motor 16 can drive the two closed pumps to work at the same time.

[0113] Specifically, if the required power of the oil pump is greater than or equal to half of the rated power of the motor 16, it means that the motor 16 can only drive one closed pump to work at the same time. If the motor 16 drives two closed pumps to work at the same time, the actual power of the motor 16 will exceed the rated power. When the required power of the oil pump is less than half of the rated power of the motor 16, the motor 16 can drive the two closed pumps to work at the same time and will not exceed the rated power.

[0114] Through steps S1200 to S1500 , the piston rod of the hydraulic cylinder 1 can have the maximum extension and retraction speed without exceeding the rated power of the motor 16 .

[0115] Optionally, see Figure 4 , the control method of the closed hydraulic system further includes the following steps after step S1500;

[0116] S1600: Determine whether the working quadrant of the closed hydraulic system is the second quadrant.

[0117] If not, execute S700; if so, execute S1700.

[0118] S1700: Determine whether the opening of the joystick exceeds the set opening based on the position of the joystick.

[0119] The opening of the joystick is proportional to the deviation of the joystick from the initial position, so the deviation of the joystick from the initial position can be determined according to the position of the joystick, and then the opening of the joystick can be determined. The setting opening can be set according to actual needs. In this embodiment, an exemplary solution of setting the opening to 50% is given.

[0120] If yes, execute S1800; if no, execute S700.

[0121] S1800: The motor 16 generates electricity and stores it in the battery.

[0122] In S1400, when only the first closed pump 3 is turned on, the motor 16 is made to execute the speed of the corresponding working quadrant regardless of whether the working quadrant of the closed hydraulic system is the first quadrant or the second quadrant. However, in S1500, when the first closed pump 3 and the second closed pump 9 are turned on at the same time, they are controlled according to different situations. When the working quadrant of the closed hydraulic system is the first quadrant, the motor 16 can execute the speed of the corresponding working quadrant, but when the working quadrant of the hydraulic system is the second quadrant, the piston rod of the hydraulic cylinder 1 is subjected to a negative load. When the piston rod needs to retract quickly, the oil can be used to drive the first closed pump 3 and the second closed pump 9 to reverse, so that the motor 16 generates electricity and recovers energy; when the piston rod does not need to retract quickly, the speed of the motor 16 can be controlled according to actual needs.

[0123] Therefore, when the hydraulic system is in the second quadrant, the degree of opening of the operating handle is also used to determine whether the driver expects the piston rod to retract quickly. If so, power generation can be performed. If not, the motor 16 is made to execute the speed of the corresponding working quadrant.

[0124] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A closed hydraulic system, comprising an oil replenishment pump (2), a hydraulic cylinder (1) and a first closed pump (3), wherein the input end of the oil replenishment pump (2) is connected to an oil tank (5), the output end of the oil replenishment pump (2) is connected to an oil replenishment oil circuit (6), the hydraulic cylinder (1) has a rod chamber (101) and a rodless chamber (102), one end of the first closed pump (3) is connected to a first oil circuit (7), the first oil circuit (7) is connected to the rodless chamber (102), the other end of the first closed pump (3) is connected to a second oil circuit (8), the second oil circuit (8) is connected to the rod chamber (101), and the first closed pump (3) can rotate forward and reverse; characterized in that: The closed hydraulic system further comprises a balancing valve (4), wherein the balancing valve (4) is configured to allow the one with the smaller oil pressure between the first oil circuit (7) and the second oil circuit (8) to communicate with the oil replenishment circuit (6).

2. The closed hydraulic system according to claim 1, characterized in that: The closed hydraulic system also includes: a second closed pump (9), the second closed pump (9) being capable of forward and reverse rotation, one end of the second closed pump (9) being connected to the oil replenishment circuit (6), and the other end of the second closed pump (9) being connected to the third oil circuit (10), the third oil circuit (10) being in communication with the first oil circuit (7); A first reversing valve (11) is arranged in the third oil circuit (10), and the first reversing valve (11) is used to control the connection and disconnection of the third oil circuit (10).

3. The closed hydraulic system according to claim 2, characterized in that: The closed hydraulic system further comprises a motor (16) and a battery electrically connected to the motor (16); the motor (16) is simultaneously connected to the first closed pump (3) and the second closed pump (9) in a transmission manner, and the motor (16) can simultaneously drive the first closed pump (3) and the second closed pump (9) to rotate; and when the first closed pump (3) pumps oil into the first oil circuit (7), the second closed pump (9) pumps oil into the third oil circuit (10).

4. The closed hydraulic system according to claim 3, characterized in that: The closed hydraulic system also includes: a first bypass oil circuit (12), wherein two ends of the first bypass oil circuit (12) are respectively connected to the oil replenishment circuit (6) and the third oil circuit (10), and a connection point between the first bypass oil circuit (12) and the third oil circuit (10) is located between the second closed pump (9) and the first reversing valve (11); The second reversing valve (13) is arranged in the first bypass oil circuit (12), and the second reversing valve (13) is used to control the connection and disconnection of the first bypass oil circuit (12).

5. The closed hydraulic system according to claim 3, characterized in that: The closed hydraulic system also includes: a second bypass oil circuit (14), wherein two ends of the second bypass oil circuit (14) are respectively connected to the oil replenishment circuit (6) and the third oil circuit (10), and a connection point between the second bypass oil circuit (14) and the third oil circuit (10) is located between the second closed pump (9) and the first reversing valve (11); A one-way valve (15) is provided in the second bypass oil passage (14), and the one-way valve (15) is configured to only allow oil to flow from the oil replenishment passage (6) through the second bypass oil passage (14) to the third oil passage (10).

6. The closed hydraulic system according to any one of claims 1 to 5, characterized in that: The closed hydraulic system further comprises a regeneration oil circuit (17) connected between the first oil circuit (7) and the second oil circuit (8), and a regeneration valve (18) arranged in the regeneration oil circuit (17), wherein the regeneration valve (18) is used to control the connection and disconnection of the regeneration oil circuit (17).

7. The closed hydraulic system according to any one of claims 1 to 5, characterized in that: The closed hydraulic system further comprises a first overflow valve (19) connected between the oil replenishment circuit (6) and the first oil circuit (7), wherein the first overflow valve (19) is configured to allow the oil in the first oil circuit (7) to overflow to the oil replenishment circuit (6) when the oil pressure exceeds a first set pressure. The closed hydraulic system further comprises a second overflow valve (20) connected between the oil replenishment circuit (6) and the second oil circuit (8), wherein the second overflow valve (20) is configured to allow the oil in the second oil circuit (8) to overflow to the oil replenishment circuit (6) when the oil pressure exceeds a second set pressure.

8. The closed hydraulic system according to any one of claims 1 to 5, characterized in that: The closed hydraulic system further comprises an oil replenishment overflow valve (21) connected between the oil replenishment circuit (6) and the oil tank (5), wherein the oil replenishment overflow valve (21) is configured to enable the oil in the oil replenishment circuit (6) to overflow into the oil tank (5) when the oil exceeds a third set pressure.

9. The closed hydraulic system according to any one of claims 1 to 5, characterized in that: The balancing valve (4) comprises a first interface, a second interface and a third interface, the first interface being in communication with the first oil circuit (7), the second interface being in communication with the second oil circuit (8), and the third interface being in communication with the oil replenishment circuit (6); when the oil pressure of the first oil circuit (7) is greater than the oil pressure of the second oil circuit (8), the balancing valve (4) enables the second interface to be in communication with the third interface, and the first interface to be disconnected; when the oil pressure of the first oil circuit (7) is less than the oil pressure of the second oil circuit (8), the balancing valve (4) enables the first interface to be in communication with the third interface, and the second interface to be disconnected.

10. A vehicle, characterized in that: The closed hydraulic system comprises the closed hydraulic system according to any one of claims 1 to 9, wherein the hydraulic cylinder (1) is a boom cylinder, a dipper arm cylinder or a bucket cylinder.

11. A control method for a closed hydraulic system, characterized in that: The closed hydraulic system according to claim 1 is implemented, wherein the closed hydraulic system further comprises a second closed pump (9) and a motor (16), wherein the second closed pump (9) can rotate forward and reverse, wherein one end of the second closed pump (9) is connected to the oil replenishment circuit (6), and the other end is connected to the third oil circuit (10), wherein the third oil circuit (10) is connected to the first oil circuit (7); the motor (16) is simultaneously connected to the first closed pump (3) and the second closed pump (9), and the motor (16) can simultaneously drive the first closed pump (3) and the second closed pump (9) to rotate; and the control method of the closed hydraulic system comprises: Get the position of the joystick; Determining the extension and retraction requirements of the piston rod of the hydraulic cylinder (1) based on the position of the operating handle; Obtaining a high-pressure oil chamber of the hydraulic oil cylinder (1), wherein the high-pressure oil chamber of the hydraulic oil cylinder (1) is the one with the greater oil pressure between the rod chamber (101) and the rodless chamber (102) of the hydraulic oil cylinder (1); Obtaining the correspondence between the extension and retraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder (1) and the working quadrant of the closed hydraulic system, wherein the working quadrant of the closed hydraulic system includes a first quadrant, a second quadrant, a third quadrant and a fourth quadrant; Determining the working quadrant of the closed hydraulic system based on the extension and retraction requirements of the piston rod, the high-pressure oil chamber of the hydraulic cylinder (1) and the corresponding relationship; Determine whether the working quadrant of the closed hydraulic system is the third quadrant or the fourth quadrant; If so, the rotational speed of the motor (16) is determined based on the operating quadrant.

12. The closed hydraulic system control method according to claim 11, characterized in that: When determining whether the working quadrant of the closed hydraulic system is the third quadrant or the fourth quadrant, if not, the control method of the closed hydraulic system further includes: Determining a required rotation speed of the motor (16) based on the position of the joystick; determining a required flow rate of the oil pump based on the required speed; Obtaining the maximum oil pressure of the oil pressure in the rod chamber (101) and the oil pressure in the rodless chamber (102); determining a required power of the oil pump based on the required flow rate and the maximum oil pressure; Get the rated power of the motor (16); Determine the magnitude of the required power of the oil pump and half of the rated power of the motor (16); If the required power of the oil pump is greater than or equal to half of the rated power of the motor (16), only the first closed pump (3) is turned on; if the required power of the oil pump is less than half of the rated power of the motor (16), the first closed pump (3) and the second closed pump (9) are turned on simultaneously.

13. The closed hydraulic system control method according to claim 12, characterized in that: After the first closed pump (3) and the second closed pump (9) are turned on simultaneously, the control method of the closed hydraulic system further comprises: Determine whether the working quadrant of the closed hydraulic system is the second quadrant; If not, the rotational speed of the motor (16) is determined based on the operating quadrant.

14. The closed hydraulic system control method according to claim 13, characterized in that: The closed hydraulic system further comprises a battery electrically connected to the motor (16); When determining whether the working quadrant of the closed hydraulic system is the second quadrant, if so, the control method of the closed hydraulic system further includes: determining whether the opening of the joystick exceeds a set opening based on the position of the joystick; If so, the motor (16) generates electricity and stores it in the battery; if not, the rotation speed of the motor (16) is determined based on the working quadrant.

Images