Hydraulic load simulation active-passive multi-working condition loading method and hydraulic system

Abstract

The application provides a hydraulic load simulation active and passive, multi-working condition loading method and a hydraulic system, and the application realizes passive loading and active loading of hydraulic load simulation through a load simulation hydraulic system with a loading hydraulic pump, an oil supplement pump, a load simulation hydraulic cylinder and a three-way proportional pressure reducing overflow valve group as the main body, and positive load and negative load working condition simulation can be realized. The application can effectively realize active loading and passive loading of hydraulic load simulation through two modes of pressure reduction and overflow of the three-way proportional pressure reducing overflow valve and combined oil supply of the loading pump and the oil supplement pump. In addition, in the active loading mode, active extension and active retraction of the load simulation hydraulic cylinder can be adjusted, and the active extension and active retraction pressure can be adjusted by the three-way proportional pressure reducing overflow valve, so that four working condition simulations of positive load working condition 1, positive load working condition 2, negative load working condition 1 and negative load working condition 2 can be realized.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic transmission and control, specifically relating to a hydraulic load simulation method for active and passive loading under multiple working conditions and a hydraulic system. Background Technology

[0002] In the field of hydraulic transmission, when testing and verifying the response characteristics and electro-hydraulic control algorithms of the actuators of experimental devices, it is necessary to simulate the actual working conditions of the experimental equipment as closely as possible. This is done by simulating the load faced by the actuator through mechanical or hydraulic loading. Hydraulic load simulation involves applying specific resistance or torque to a hydraulic cylinder or hydraulic motor to simulate the load value of the actuator, such as the hydraulic cylinder or hydraulic motor under test, in order to simulate and verify the response and self-regulation performance of the actuator under complex and variable external load conditions.

[0003] In linear motion, hydraulic load simulation primarily utilizes a combination of a load-simulating hydraulic cylinder and a proportional relief valve, proportional throttle valve, or balance valve. The load force is simulated by setting the valve opening degree to create a certain back pressure, and the set back pressure can be controlled by an external electrical signal. When using a proportional relief valve, the opening pressure can be set via an external electrical signal, and this opening pressure can be used as the simulated load force. When using a proportional throttle valve, the opening degree can be controlled by an external signal; different opening degrees correspond to different fluid resistances to simulate the magnitude of the external load force.

[0004] In linear motion, existing hydraulic load simulation methods are all passive loading methods. This involves combining a load simulation hydraulic cylinder with a proportional relief valve, proportional throttle valve, or balance valve. Based on the principle of hydraulic resistance control, the load force is simulated by setting the valve opening to create a certain back pressure. These load simulation hydraulic cylinders are all passive; they cannot actively extend or retract, nor can they actively generate and apply load force. Only when the external actuator applies its main power to the load simulation hydraulic cylinder can the load simulation hydraulic system generate a certain load force through the proportional relief valve, proportional throttle valve, or balance valve. When the external actuator does not apply any active force to the load simulation hydraulic cylinder, the load simulation cannot apply a reverse load force and therefore cannot complete the load simulation function.

[0005] In general, traditional load simulation methods fail when the following operating conditions occur:

[0006] (1) Positive load condition 1, that is, the main power of the external actuator is thrust, and the load simulation cylinder needs to actively extend when it needs to actively apply a load force opposite to the direction of movement of the external actuator. Traditional load simulation methods cannot achieve active loading condition 1 because there is no active hydraulic loading power source and the direction of hydraulic fluid cannot be changed.

[0007] (2) Positive load condition 2, that is, the main power of the external actuator is the tension, and the load simulation cylinder is required to actively retract when it actively applies a load force opposite to the direction of movement of the external actuator. Traditional load simulation methods cannot achieve active loading condition 2 because they do not have an active hydraulic loading power source and the direction of hydraulic fluid cannot be changed.

[0008] (3) Negative load condition 1, that is, the main power of the external actuator is thrust, and the load simulation cylinder needs to actively apply the load force in the same direction as the movement of the external actuator to actively retract. Traditional load simulation methods cannot achieve negative load condition 1 because there is no active hydraulic loading power source and the direction of hydraulic fluid cannot be changed.

[0009] (4) Negative load condition 2, that is, the main power of the external actuator is the tension, and the load simulation cylinder needs to actively extend when it actively applies the load force in the same direction as the movement of the external actuator. Traditional load simulation methods cannot achieve negative load condition 2 because they do not have an active hydraulic loading power source and the direction of hydraulic fluid cannot be changed.

[0010] In addition, traditional load simulation methods can only complete the loading of a single working condition and cannot simultaneously complete the load simulation loading of multiple working conditions, which has great limitations for the needs of multi-working-condition simulation loading tests. Summary of the Invention

[0011] Traditional hydraulic load simulation systems can only achieve passive loading, not active loading; they can only simulate positive load conditions, not negative load conditions; and they can only simulate a single condition, failing to meet the needs of multi-condition simulation loading tests. This invention addresses the shortcomings of traditional hydraulic load simulation systems by proposing a hydraulic load simulation method and hydraulic system that supports both passive and active loading under multiple conditions. Based on a three-way proportional pressure-reducing relief valve, this invention constructs a load simulation hydraulic system primarily composed of a loading hydraulic pump, a replenishing pump, a load simulation hydraulic cylinder, and a three-way proportional pressure-reducing relief valve assembly. This system can achieve not only passive loading in traditional load simulation but also active loading, and can simulate both positive and negative load conditions. The proposed hydraulic load simulation method for active and passive loading under multiple conditions is mainly implemented using a hydraulic system consisting of a loading hydraulic pump, a replenishing pump, a three-way proportional pressure-reducing relief valve assembly, a load simulation hydraulic cylinder, an actuator hydraulic cylinder, a motor, a three-position four-way directional valve, a relief valve, an unloading valve, a check valve, and an oil tank.

[0012] The technical solution of the present invention is as follows:

[0013] This invention first provides a hydraulic load simulation active and passive multi-condition loading method and hydraulic system, the system including an oil tank, a loading pump, a replenishing pump, a three-position four-way directional valve, a first three-way proportional pressure reducing relief valve, a second three-way proportional pressure reducing relief valve, an actuating hydraulic cylinder, a load simulation hydraulic cylinder, a relief valve and an unloading valve.

[0014] The suction ports of the loading pump and the replenishing pump are connected to the oil tank. The P port of the three-position four-way directional valve is connected to the outlet port of the loading pump. The T port of the three-position four-way directional valve is connected to the oil tank. The A and B ports of the three-position four-way directional valve are connected to the A ports of the first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve, respectively. The T ports of the first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve are connected to the oil tank.

[0015] The rod-side port and rodless port of the load-simulating hydraulic cylinder are connected to port B of the first three-way proportional pressure reducing relief valve and port B of the second three-way proportional pressure reducing relief valve, respectively.

[0016] The outlet of the replenishing pump is connected to port A of the first three-way proportional pressure reducing relief valve and port A of the second three-way proportional pressure reducing relief valve via the second check valve and the third check valve, respectively.

[0017] The hydraulic cylinder is connected to the piston rod of the load simulation hydraulic cylinder via a hinge mechanism; the relief valve and the unloading valve are connected in parallel to form a safety valve group, one end of which is connected to the oil tank and the other end is connected to the outlet of the loading pump.

[0018] The present invention also provides an active and passive multi-condition loading method based on the hydraulic system. The method realizes active and passive loading of hydraulic load simulation by using the pressure reduction and overflow modes of the first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve, as well as the combination of loading pump and replenishing pump for oil supply.

[0019] In the passive loading mode, the three-way proportional pressure reducing relief valve is in reverse flow state and is in overflow mode. By adjusting the set pressure of the three-way proportional pressure reducing relief valve, the load simulation force is changed to perform passive loading. At this time, the loading hydraulic pump of the hydraulic system is turned off, the load simulation hydraulic cylinder cannot actively extend and retract, and the oil replenishment pump is turned on to replenish the oil required by the load simulation hydraulic cylinder.

[0020] In active loading mode, the three-way proportional pressure reducing relief valve is in a positive flow state and is in pressure reducing mode. By adjusting the set pressure of the three-way proportional pressure reducing relief valve, the active extension and active retraction pressure of the load simulation hydraulic cylinder can be changed to achieve active loading, thereby realizing four working conditions simulation: positive load condition 1, positive load condition 2, negative load condition 1, and negative load condition 2.

[0021] Furthermore, when simulating positive load condition 1, the condition simulation is completed by loading the hydraulic pump and adjusting the outlet pressure of the second three-way proportional pressure reducing relief valve in the rodless chamber oil circuit of the load-simulating hydraulic cylinder.

[0022] When simulating positive load condition 2, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the outlet pressure of the first three-way proportional pressure reducing relief valve in the rod chamber oil circuit of the hydraulic cylinder.

[0023] When simulating the negative load condition 1, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the pressure of the first three-way proportional pressure reducing relief valve in the rod chamber oil circuit of the hydraulic cylinder.

[0024] When simulating the negative load condition 2, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the pressure of the second three-way proportional pressure reducing relief valve in the rodless chamber oil circuit of the hydraulic cylinder.

[0025] Compared with existing technologies, this invention proposes a hydraulic load simulation method with active and passive loading modes, and multiple operating conditions. By utilizing the pressure reduction and relief modes of a three-way proportional pressure reducing relief valve, and the combined oil supply of a loading pump and a replenishing pump, both active and passive loading modes of hydraulic load simulation can be effectively achieved. Furthermore, in the active loading mode, the active extension and retraction of the load simulation hydraulic cylinder can be adjusted, and the active extension and retraction pressures can be set by the three-way proportional pressure reducing relief valve, enabling simulation of four operating conditions: positive load condition 1, positive load condition 2, negative load condition 1, and negative load condition 2. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the hydraulic system of the present invention.

[0027] 1-Oil tank, 2-Loading pump, 3-Three-phase motor I, 4-First check valve, 5-Unloading valve, 6-Relief valve, 7-Three-position four-way directional valve, 8-Maintenance pump, 9-Three-phase motor II, 10-Second check valve, 11-Third check valve, 12-First three-way proportional pressure reducing relief valve, 13-Second three-way proportional pressure reducing relief valve, 14-Hinged mechanism, 15-Actuating hydraulic cylinder, 16-Load simulation hydraulic cylinder. Detailed Implementation

[0028] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0029] like Figure 1The diagram shows a hydraulic load simulation method for active and passive multi-condition loading and a schematic diagram of the hydraulic system. The hydraulic system mainly includes an oil tank 1, a loading pump 2, a three-phase motor I 3, a first check valve 4, an unloading valve 5, a relief valve 6, a three-position four-way directional valve 7, a replenishing pump 8, a three-phase motor II 9, a second check valve 10, a third check valve 11, a first three-way proportional pressure reducing relief valve 12, a second three-way proportional pressure reducing relief valve 13, a hinge mechanism 14, an actuating hydraulic cylinder 15, and a load simulation hydraulic cylinder 16.

[0030] The suction ports of the loading pump 2 and the replenishing pump 8 are connected to the oil tank 1. The 7P port of the three-position four-way directional valve 7 is connected to the oil outlet of the loading pump 2. The 7T port of the three-position four-way directional valve 7 is connected to the oil tank 1. The 7A and 7B ports of the three-position four-way directional valve 7 are connected to the 12A port of the first three-way proportional pressure reducing relief valve 12 and the 13A port of the second three-way proportional pressure reducing relief valve 13, respectively. The 12T port of the first three-way proportional pressure reducing relief valve 12 and the 13T port of the second three-way proportional pressure reducing relief valve 13 are connected to the oil tank. The rod-side port 16A and the rodless-side port 16B of the load simulation hydraulic cylinder 16 are connected to the 12B port of the first three-way proportional pressure reducing relief valve 12 and the 13B port of the second three-way proportional pressure reducing relief valve 13, respectively. The second check valve 4 and the third check valve 11 at the outlet of the replenishing pump 8 are connected to port 12A of the first three-way proportional pressure reducing relief valve 12 and port 13A of the second three-way proportional pressure reducing relief valve 13, respectively. The actuating hydraulic cylinder 15 is connected to the piston rod of the load simulation hydraulic cylinder 16 via the hinge mechanism 14. The safety valve group, consisting of the relief valve 6 and the unloading valve 5 connected in parallel, is connected in parallel to the high-pressure main oil line of the loading pump 2. That is, one end of the safety valve group is connected to the oil tank, and the other end is connected to the outlet of the loading pump. It should be noted that the set pressure of the relief valve 6 should be higher than the maximum pressure limit of the system to protect the normal operation of the hydraulic system. The outlet pressure of the replenishing pump 2 is generally set not to exceed 2.5 MPa. When the system is not working, the solenoid 1DT of the unloading valve 5, the left solenoid 2DT and the right solenoid 3DT of the three-position four-way directional valve 7 are all de-energized.

[0031] It should be noted that the hydraulic system principle appended to this invention... Figure 1 The first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve 13 used are pilot-operated three-way proportional pressure reducing relief valves, which can also be replaced by direct-acting three-way proportional pressure reducing valves, and are also within the protection scope of this invention.

[0032] This invention can not only realize passive loading in traditional load simulation, but also active loading in load simulation, and can simulate positive and negative load conditions.

[0033] This invention proposes a hydraulic load simulation method and hydraulic system that supports both active and passive loading under multiple operating conditions. The passive loading method involves adjusting the set pressures of the first and second three-way proportional pressure-reducing relief valves to change the load simulation force, thereby achieving passive loading. During this process, the loading hydraulic pump is shut off, the load simulation hydraulic cylinder cannot actively extend or retract, and a replenishing pump is used to supply the hydraulic fluid required by the load simulation hydraulic cylinder.

[0034] The present invention proposes a hydraulic load simulation method with active and passive loading under multiple working conditions. Its active loading method can simulate positive load conditions and negative load conditions. (1) Positive load condition 1, that is, when the main power of the external actuator is thrust, and the load simulation hydraulic cylinder needs to actively apply a load force opposite to the direction of movement of the external actuator, this condition can be simulated by loading the hydraulic pump and adjusting the outlet pressure of the second three-way proportional pressure reducing relief valve of the rodless chamber oil circuit of the load hydraulic cylinder. (2) Positive load condition 2, that is, when the main power of the external actuator is tension, and the load simulation hydraulic cylinder needs to actively apply a load force opposite to the direction of movement of the external actuator, this condition can be simulated by loading the hydraulic pump and adjusting the outlet pressure of the first three-way proportional pressure reducing relief valve of the rod chamber oil circuit of the load hydraulic cylinder. (3) Negative load condition 1, that is, when the main power of the external actuator is thrust, and the load simulation hydraulic cylinder is required to actively apply a load force in the same direction as the movement of the external actuator, this condition can be simulated by loading the hydraulic pump and adjusting the pressure of the first three-way proportional pressure reducing relief valve in the rod chamber oil circuit of the load hydraulic cylinder. (4) Negative load condition 2, that is, when the main power of the external actuator is tension, and the load simulation hydraulic cylinder is required to actively apply a load force in the same direction as the movement of the external actuator, this condition can be simulated by loading the hydraulic pump and adjusting the pressure of the second three-way proportional pressure reducing relief valve in the rodless chamber oil circuit of the load hydraulic cylinder.

[0035] The first three-way proportional pressure reducing overflow valve and the second three-way proportional pressure reducing overflow valve of this invention have an oil inlet, an oil outlet, and an overflow port, and have both pressure reducing and overflow functions. The oil inlet is connected to the high-pressure main oil circuit, the oil outlet is connected to the working oil circuit, and the overflow port is connected to the oil tank. Through an internal regulating device, the pressure of the inlet high-pressure main oil circuit is regulated and reduced to the pressure reducing pressure required at the oil outlet, while also having a full-flow overflow function from the oil outlet to the overflow port. When the liquid flow is reversed, if the pressure at the oil outlet is less than the set required pressure, it also has the function of reverse flow from the oil outlet to the oil inlet. The pressure drop between the oil outlet and the overflow port can be set and adjusted by an external control signal.

[0036] The following section combines the principles of hydraulic systems. Figure 1 The present invention further describes a hydraulic load simulation method for active and passive loading under multiple working conditions, as well as a hydraulic system thereof.

[0037] (1) Passive loading method for simulating load on hydraulic systems

[0038] When the main power of the actuating hydraulic cylinder 15 is thrust, and it acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 to form a pushing force, the passive loading method provides a passive load loading force to the load simulation hydraulic cylinder 16 in the opposite direction to the extension direction of the actuating hydraulic cylinder. Specifically, the loading pump 2 is in the closed state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is de-energized, and the right solenoid 3DT is energized to connect its 7P port and 7B port, and its 7A port and 7T port. Under the thrust of hydraulic cylinder 15, the load simulation hydraulic cylinder 16 retracts to the right. Oil in its rod chamber is replenished by the oil pump 8, while oil in its rodless chamber flows through port 16B to the second three-way proportional pressure reducing relief valve 13. At this time, the second three-way proportional pressure reducing relief valve 13 is in a reverse flow state, with oil flowing through port 13B to port 13A. Since the outlet of port 13A is not connected to the oil tank, the pressure at ports 13A and 13B will increase. When the pressure at port 13B rises to the set pressure of the second three-way proportional pressure reducing relief valve 13, port 13B connects to port 13T and overflows, while port 13A disconnects from port 13B. At this time, the second three-way proportional pressure reducing relief valve 13 is in overflow mode, forming the set load simulation pressure to achieve passive loading. It should be noted that for the second three-way proportional pressure reducing relief valve 13, when the pressure at port 13B is less than the external set pressure, port 13B is connected to port 13A; when the pressure at port 13B is greater than the external set pressure, port 13B and port 13T are connected to open the relief mode. The set pressure of the second three-way proportional pressure reducing relief valve 13 can be set by an external control signal.

[0039] When the main power of the actuating hydraulic cylinder 15 is a pulling force, which acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 and forms a pulling force on it, the passive loading method provides a passive load loading force to the load simulation hydraulic cylinder 16 in the opposite direction to the retraction direction of the actuating hydraulic cylinder. Specifically, the loading pump 2 is in the closed state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is energized and the right solenoid 3DT is de-energized to connect its 7P port to its 7A port and its 7B port to its 7T port. Under the pulling force of hydraulic cylinder 15, the load simulation hydraulic cylinder 16 extends to the left. The oil in its rodless chamber is replenished by the oil pump 8, while the oil in its rod chamber flows through port 16A to the first three-way proportional pressure reducing relief valve 12. At this time, the first three-way proportional pressure reducing relief valve 12 is in a reverse flow state, and the oil flows through port 12B to port 12A. Since the outlet of port 12A is not connected to the oil tank, the pressure at ports 12A and 12B will increase. When the pressure at port 12B rises to the set pressure of the three-way proportional pressure reducing relief valve 12, port 12B connects to port 12T and overflows, while port 12A disconnects from port 12B. At this time, the first three-way proportional pressure reducing relief valve 12 is in overflow mode, forming the set load simulation pressure to achieve the purpose of passive loading. It should be noted that for the first three-way proportional pressure reducing relief valve 12, when the pressure at port 12B is less than the external set pressure, port 12B is connected to port 12A; when the pressure at port 12B is greater than the external set pressure, port 12B and port 13T are connected to open the relief mode. The set pressure of the first three-way proportional pressure reducing relief valve 12 can be set by an external control signal.

[0040] (2) Active Loading Method for Hydraulic System Load Simulation

[0041] a. Positive load condition 1

[0042] When the main power of the actuating hydraulic cylinder 15 is thrust, and it acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 to form a pushing force, the active loading method provides an active load loading force to the load simulation hydraulic cylinder 16 in the opposite direction to the extension direction of the actuating hydraulic cylinder. At this time, the positive load condition 1 can be simulated. Specifically, the loading pump 2 is in the open state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is de-energized, and the right solenoid 3DT is energized to connect its 7P port and 7B port, and its 7A port and 7T port. The high-pressure oil from the outlet of the loading pump 2 flows through port 7P of the three-position four-way directional valve 7 and through port 7B to port 13A of the second three-way proportional pressure reducing relief valve 13. The high-pressure oil flows in from the inlet of 13A and flows out from the outlet of 13B. At this time, the second three-way proportional pressure reducing relief valve 13 is in a forward flow state. The outlet pressure is determined by the set pressure of the second three-way proportional pressure reducing relief valve 13. The pressure oil after pressure reduction flows from port 13B through port 16B to the rodless chamber of the load simulation hydraulic cylinder 16, forming an active extension load loading force to the left of the load simulation hydraulic cylinder 16 to resist the main power of the actuator hydraulic cylinder 15. It should be noted that if the outlet pressure of the second three-way proportional pressure reducing relief valve 13 is greater than the main power of the actuator hydraulic cylinder 15, the load simulation hydraulic cylinder 16 extends to the left, and the actuator hydraulic cylinder 15 is forced to retract to the left; if the outlet pressure of the second three-way proportional pressure reducing relief valve 13 is less than the main power of the actuator hydraulic cylinder 15, the load simulation hydraulic cylinder 16 is forced to retract to the right. At this time, in order to prevent the rod chamber of the load simulation hydraulic cylinder 16 from sucking in air, the oil replenishment pump 8 replenishes oil to the rod chamber of the load simulation hydraulic cylinder 16 through the second check valve 10.

[0043] b. Positive load condition 2

[0044] When the main power of the actuating hydraulic cylinder 15 is tension, and it acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 to form a tension force, the active loading method provides an active load loading force to the load simulation hydraulic cylinder 16 in the opposite direction to the retraction direction of the actuating hydraulic cylinder. At this time, the positive load condition 2 can be simulated. Specifically, the loading pump 2 is in the open state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is energized and the right solenoid 3DT is de-energized to connect its 7P port to its 7A port and its 7B port to its 7T port. The high-pressure oil from the outlet of the loading pump 2 flows through the 7P port of the three-position four-way directional valve 7 and through the 7A port to the 12A port of the first three-way proportional pressure reducing relief valve 12. The high-pressure oil flows in from the 12A inlet and flows out from the 12B outlet. At this time, the first three-way proportional pressure reducing relief valve 12 is in a forward flow state. The outlet pressure is determined by the set pressure of the first three-way proportional pressure reducing relief valve 12. The pressure oil after pressure reduction flows from the 12B port through the 16A port to the rod chamber of the load simulation hydraulic cylinder 16, forming a rightward active retraction load loading force on the load simulation hydraulic cylinder 16 to resist the main power of the actuator hydraulic cylinder 15. It should be noted that if the outlet pressure of the first three-way proportional pressure reducing relief valve 12 is greater than the main power of the actuator hydraulic cylinder 15, the load simulation hydraulic cylinder 16 retracts to the right, and the actuator hydraulic cylinder 15 is forced to extend to the right; if the outlet pressure of the first three-way proportional pressure reducing relief valve 12 is less than the main power of the actuator hydraulic cylinder 15, the load simulation hydraulic cylinder 16 is forced to extend to the left. At this time, in order to prevent the rodless chamber of the load simulation hydraulic cylinder 16 from sucking in air, the oil replenishment pump 8 replenishes oil to the rodless chamber of the load simulation hydraulic cylinder 16 through the third check valve 11.

[0045] c. Negative load condition 1

[0046] When the main power of the actuating hydraulic cylinder 15 is thrust, and it acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 to form a pushing force, the active loading method provides an active load loading force to the load simulation hydraulic cylinder 16 in the same direction as the retraction direction of the actuating hydraulic cylinder. At this time, the negative load condition 1 can be simulated. Specifically, the loading pump 2 is in the open state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is energized and the right solenoid 3DT is de-energized to connect its 7P port to its 7A port and its 7B port to its 7T port. The high-pressure oil from the outlet of the loading pump 2 flows through port 7P of the three-position four-way directional valve 7 and through port 7A to port 12A of the three-way proportional pressure reducing relief valve I 12. The high-pressure oil flows in from the inlet of 12A and out from the outlet of 12B. At this time, the first three-way proportional pressure reducing relief valve 12 is in a positive flow state, and the outlet pressure is determined by the set pressure of the first three-way proportional pressure reducing relief valve 12. The pressure oil after pressure reduction flows from port 12B through port 16A to the rod chamber of the load simulation hydraulic cylinder 16, forming a rightward active retraction load loading force on the load simulation hydraulic cylinder 16. At this time, the direction of the load loading force is consistent with the direction of the active force, forming negative load condition 1. It should be noted that since the force direction of the active actuator 15 and the load simulation hydraulic cylinder 16 is consistent, the load simulation hydraulic cylinder 16 will retract rapidly to the right. In order to prevent the load simulation hydraulic cylinder 16 from sucking in cavitation due to rapid retraction, the oil replenishment pump 8 replenishes oil to the rod chamber of the load simulation hydraulic cylinder 16 through the second check valve 10 to avoid sucking in cavitation.

[0047] d. Under negative load conditions 2

[0048] When the main power of the actuating hydraulic cylinder 15 is tension, and it acts on the piston rod of the load simulation hydraulic cylinder 16 through the hinge mechanism 14 to form a tension force, the active loading method provides an active load loading force to the load simulation hydraulic cylinder 16 in the same direction as the retraction direction of the actuating hydraulic cylinder. At this time, the positive load condition 2 can be simulated. Specifically, the loading pump 2 is in the open state, the replenishing pump 8 is in the open state, the solenoid 1DT of the hydraulic system unloading valve 5 is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve 7 is de-energized, and the right solenoid 3DT is energized to connect its 7P port and 7B port, and its 7A port and 7T port. The high-pressure oil from the outlet of the loading pump 2 flows through port 7P of the three-position four-way directional valve 7 and through port 7B to port 13A of the second three-way proportional pressure reducing relief valve 13. The high-pressure oil flows in from the inlet of 13A and out from the outlet of 13B. At this time, the second three-way proportional pressure reducing relief valve 13 is in a forward flow state, and the outlet pressure is determined by the set pressure of the second three-way proportional pressure reducing relief valve 13. The pressure oil after pressure reduction flows from port 13B through port 16B to the rodless chamber of the load simulation hydraulic cylinder 16, forming a leftward active extension load loading force on the load simulation hydraulic cylinder 16. At this time, the direction of the load loading force is consistent with the direction of the active force, forming negative load condition 2. It should be noted that since the force direction of the active actuator 15 and the load simulation hydraulic cylinder 16 is consistent, the load simulation hydraulic cylinder 16 will extend rapidly to the left. In order to prevent the load simulation hydraulic cylinder 16 from sucking in cavitation due to rapid extension, the oil replenishment pump 8 replenishes oil to the rodless chamber of the load simulation hydraulic cylinder 16 through the third check valve 11 to avoid sucking in cavitation.

[0049] As described above, the three-way proportional pressure reducing overflow valve of this invention has an inlet, an outlet, and an overflow port, providing both pressure reducing and overflow functions. The inlet is connected to the high-pressure main oil circuit, the outlet is connected to the working oil circuit, and the overflow port is connected to the oil tank. Through an internal regulating device, the pressure in the inlet high-pressure main oil circuit is reduced to the pressure reduction pressure required at the outlet, while simultaneously providing full-flow overflow from the outlet to the overflow port. When the liquid flow reverses, if the outlet pressure is less than the set required pressure, reverse flow from the outlet to the inlet is also possible. The pressure drop between the outlet and the overflow port can be adjusted by an external control signal.

[0050] Two three-way proportional pressure reducing relief valves are connected to the rod chamber and rodless chamber oil circuits of the load simulation hydraulic cylinder, respectively. The pressure of the three-way proportional pressure reducing relief valves can be set separately to control the active extension force and active retraction force of the load simulation hydraulic cylinder.

[0051] This invention provides a combination of a loading pump and a replenishing pump, which can be freely switched on and off according to working conditions. The loading pump needs to be activated during active loading and deactivated during passive loading. This invention adds a replenishing pump to prevent cavitation in the load-simulating hydraulic cylinder. The replenishing pump is located in the oil lines of the three-position four-way directional valve's working port and the three-way proportional pressure reducing valve's inlet. The replenishing pump is activated in a timely manner according to the working mode of the load-simulating hydraulic cylinder to prevent cavitation.

[0052] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for simulating active and passive, multi-condition loading of hydraulic loads, characterized in that, The method is based on a hydraulic load simulation active and passive multi-condition loading hydraulic system, which includes an oil tank, a loading pump, a replenishing pump, a three-position four-way directional valve, a first three-way proportional pressure reducing relief valve, a second three-way proportional pressure reducing relief valve, an actuating hydraulic cylinder, a load simulation hydraulic cylinder, a relief valve, and an unloading valve. The suction ports of the loading pump and the replenishing pump are connected to the oil tank. The P port of the three-position four-way directional valve is connected to the outlet port of the loading pump. The T port of the three-position four-way directional valve is connected to the oil tank. The A and B ports of the three-position four-way directional valve are connected to the A ports of the first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve, respectively. The T ports of the first three-way proportional pressure reducing relief valve and the second three-way proportional pressure reducing relief valve are connected to the oil tank. The rod-side port and rodless port of the load-simulating hydraulic cylinder are connected to port B of the first three-way proportional pressure reducing relief valve and port B of the second three-way proportional pressure reducing relief valve, respectively. The outlet of the replenishing pump is connected to port A of the first three-way proportional pressure reducing relief valve and port A of the second three-way proportional pressure reducing relief valve via the second check valve and the third check valve, respectively. The hydraulic cylinder is connected to the piston rod of the load simulation hydraulic cylinder through a hinge mechanism; the relief valve and the unloading valve are connected in parallel to form a safety valve group, one end of which is connected to the oil tank and the other end is connected to the outlet of the loading pump. By using the pressure reduction and overflow modes of the first three-way proportional pressure reducing and overflow valve and the second three-way proportional pressure reducing and overflow valve, as well as the combination of loading pump and replenishing pump for oil supply, the two modes of active loading and passive loading of hydraulic load simulation are realized. In the passive loading mode, the three-way proportional pressure reducing relief valve is in reverse flow state and is in overflow mode. By adjusting the set pressure of the three-way proportional pressure reducing relief valve, the load simulation force is changed to perform passive loading. At this time, the loading hydraulic pump of the hydraulic system is turned off, the load simulation hydraulic cylinder cannot actively extend and retract, and the oil replenishment pump is turned on to replenish the oil required by the load simulation hydraulic cylinder. In active loading mode, the three-way proportional pressure reducing relief valve is in a positive flow state and is in pressure reducing mode. By adjusting the set pressure of the three-way proportional pressure reducing relief valve, the active extension and active retraction pressure of the load simulation hydraulic cylinder can be changed to achieve active loading, thereby realizing four working conditions simulation: positive load condition 1, positive load condition 2, negative load condition 1, and negative load condition 2. Among them, positive load condition 1 is a condition in which the main power of the external actuator is thrust, and the load simulation hydraulic cylinder needs to actively apply a load force opposite to the direction of movement of the external actuator. Positive load condition 2, which is the main power of the external actuator is tension, and the load simulation hydraulic cylinder needs to actively apply a load force opposite to the direction of movement of the external actuator. Negative load condition 1, which is the main power of the external actuator is thrust, and the load simulation hydraulic cylinder needs to actively apply the load force in the same direction as the movement of the external actuator. Negative load condition 2, which is the main power of the external actuator is tension, and the load simulation hydraulic cylinder needs to actively apply the load force in the same direction as the movement of the external actuator.

2. The method according to claim 1, characterized in that, The relief valve is set at a pressure higher than the maximum system pressure to protect the normal operation of the hydraulic system. The outlet pressure of the replenishing pump is set not to exceed 2.5 MPa. When the system is not in operation, the solenoids of the unloading valve and the two ends of the three-position four-way directional valve are de-energized.

3. The method according to claim 1, characterized in that: When simulating positive load condition 1, the condition simulation is completed by loading the hydraulic pump and adjusting the outlet pressure of the second three-way proportional pressure reducing relief valve in the rodless chamber oil circuit of the simulated hydraulic cylinder. When simulating positive load condition 2, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the outlet pressure of the first three-way proportional pressure reducing relief valve in the rod chamber oil circuit of the hydraulic cylinder. When simulating the negative load condition 1, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the pressure of the first three-way proportional pressure reducing relief valve in the rod chamber oil circuit of the hydraulic cylinder. When simulating the negative load condition 2, the condition simulation is completed by loading the hydraulic pump and adjusting the load to simulate the pressure of the second three-way proportional pressure reducing relief valve in the rodless chamber oil circuit of the hydraulic cylinder.

4. The method according to claim 1, characterized in that: When the hydraulic system load simulation is in passive loading mode, and when the main power of the actuating hydraulic cylinder is thrust, and it acts on the piston rod of the load simulation hydraulic cylinder through the articulation mechanism to form a thrusting force, the passive loading method provides a passive load loading force to the load simulation hydraulic cylinder in the opposite direction to the extension direction of the actuating hydraulic cylinder. At this time, the loading pump is in the off state, the load simulation hydraulic cylinder cannot actively extend or retract, the replenishing pump is in the on state, the hydraulic system unloading valve 1DT is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve is de-energized, and the right solenoid 3DT is energized to connect its P port to its B port and its A port to its T port; under the thrust of the actuating hydraulic cylinder, the load simulation hydraulic cylinder retracts to the right, the oil in its rod chamber is replenished by the replenishing pump, and the oil in its rodless chamber flows to the second three-way proportional pressure reducing relief valve, at this time the second three-way proportional pressure reducing relief valve is... In reverse flow mode, the oil flows from port B to port A. Since port A is not connected to the oil tank, the pressure at both ports A and B will increase. When the pressure at port B reaches the set pressure of the second three-way proportional pressure reducing relief valve, port B and port T of the valve connect and overflow, while port A and port B disconnect. At this time, the second three-way proportional pressure reducing relief valve is in overflow mode, forming a simulated pressure of the set load to achieve the purpose of passive loading. The set pressure of the second three-way proportional pressure reducing relief valve can be set by an external control signal.

5. The method according to claim 3, characterized in that: When the hydraulic system load simulation is in passive loading mode, and when the main power of the actuating hydraulic cylinder is tension, and it acts on the piston rod of the load simulation hydraulic cylinder through the hinge mechanism to form a tension force, the passive loading method provides a passive load loading force to the load simulation hydraulic cylinder in the opposite direction to the retraction direction of the actuating hydraulic cylinder. At this time, the loading pump is in the off state, the load simulation hydraulic cylinder cannot actively extend or retract, the replenishing pump is in the on state, the solenoid 1DT of the hydraulic system unloading valve is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve is energized and the right solenoid 3DT is de-energized to connect port P and port A, and port B and port T; under the pulling force of the actuating hydraulic cylinder, the load simulation hydraulic cylinder extends to the left, the oil in its rodless chamber is replenished by the replenishing pump, and the oil in its rod chamber flows to the first three-way proportional pressure reducing relief valve, at this time the first three-way proportional pressure reducing relief valve... The valve is in reverse flow mode, with oil flowing from port B to port A. Since port A is not connected to the oil tank, the pressure at both ports A and B will increase. When the pressure at port B rises to the set pressure of the first three-way proportional pressure reducing relief valve, port B and port T of the first three-way proportional pressure reducing relief valve are connected and overflow occurs, while port A and port B are disconnected. At this time, the first three-way proportional pressure reducing relief valve is in overflow mode, forming a simulated pressure of the set load to achieve the purpose of passive loading. The set pressure of the first three-way proportional pressure reducing relief valve can be set by an external control signal.

6. The method according to claim 3, characterized in that: When simulating positive load condition 1, the loading pump is in the open state, the replenishing pump is in the open state, the solenoid 1DT of the hydraulic system unloading valve is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve is de-energized and the right solenoid 3DT is energized to connect its P port to its B port and its A port to its T port. The high-pressure oil from the pump outlet flows through port P of the three-position four-way directional valve and then through port B to port A of the second three-way proportional pressure reducing relief valve 3. The high-pressure oil flows in from inlet A and out from outlet B. At this time, the second three-way proportional pressure reducing relief valve is in a forward flow state, and the outlet pressure is determined by the set pressure of the second three-way proportional pressure reducing relief valve. The pressure oil after pressure reduction flows from port B to the rodless chamber of the load simulation hydraulic cylinder, forming an active extension load loading force to the left of the load simulation hydraulic cylinder to resist the main power of the actuator hydraulic cylinder 15.

7. The method according to claim 3, characterized in that: When simulating positive load condition 2, the loading pump is in the open state, the replenishing pump is in the open state, the solenoid 1DT of the hydraulic system unloading valve is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve is energized and the right solenoid 3DT is de-energized to connect port P to port A and port B to port T. The high-pressure oil from the pump outlet flows through port P of the three-position four-way directional valve to port A of the first three-way proportional pressure reducing relief valve. The high-pressure oil flows in from inlet A and out from outlet B. At this time, the first three-way proportional pressure reducing relief valve is in a forward flow state, and the outlet pressure is determined by the set pressure of the first three-way proportional pressure reducing relief valve. The pressure oil after pressure reduction flows from port B to the rod chamber of the load simulation hydraulic cylinder, forming a rightward active retraction load loading force on the load simulation hydraulic cylinder to resist the main power of the actuator hydraulic cylinder 15.

8. The method according to claim 3, characterized in that: When simulating the negative load condition 1, the loading pump is in the open state, the replenishing pump is in the open state, the solenoid 1DT of the hydraulic system unloading valve is energized to disconnect its oil circuit, the left solenoid 2DT of the three-position four-way directional valve is energized and the right solenoid 3DT is de-energized to connect port P to port A and port B to port T. The high-pressure oil from the pump outlet flows through port P of the three-position four-way directional valve to port A of the first three-way proportional pressure reducing relief valve. The high-pressure oil flows in from inlet A and out from outlet B. At this time, the first three-way proportional pressure reducing relief valve is in a positive flow state, and the outlet pressure is determined by the set pressure of the first three-way proportional pressure reducing relief valve. The pressure oil after pressure reduction flows from port B to the rod chamber of the load simulation hydraulic cylinder, forming a rightward active retraction load loading force on the load simulation hydraulic cylinder. At this time, the direction of the load loading force is consistent with the direction of the active force, forming negative load condition 1.

9. The method according to claim 3, characterized in that: When simulating the negative load condition 2, the loading pump is in the open state, the replenishing pump is in the open state, the solenoid 1DT of the hydraulic system unloading valve is energized to disconnect the oil circuit, the left solenoid 2DT of the three-position four-way directional valve is de-energized, and the right solenoid 3DT is energized to connect its P port to its B port and its A port to its T port. The high-pressure oil from the pump outlet flows through port P of the three-position four-way directional valve to port A of the second three-way proportional pressure reducing relief valve via port B. The high-pressure oil flows in from inlet A and out from outlet B. At this time, the second three-way proportional pressure reducing relief valve is in a positive flow state, and the outlet pressure is determined by the set pressure of the second three-way proportional pressure reducing relief valve. The pressure oil after pressure reduction flows from port B to the rodless chamber of the load simulation hydraulic cylinder, forming a leftward active extension load loading force on the load simulation hydraulic cylinder. At this time, the direction of the load loading force is consistent with the direction of the active force, forming negative load condition 2.

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