Series oil cylinder hydraulic system, oil supplementing control method of series oil cylinder hydraulic system and operation machine

Abstract

The invention belongs to the technical field of operation machinery and provides a series oil cylinder hydraulic system, an oil supplementing control method of the series oil cylinder hydraulic system and an operation machine.The oil supplementing control method comprises the steps that when the series oil cylinder hydraulic system executes oil cylinder stretching operation, whether a first-stage oil cylinder and a second-stage oil cylinder stretch out synchronously or not is detected and judged; if the extension is not synchronous, comparing a first extension proportional stroke of the piston rod of the first-stage oil cylinder with a second extension proportional stroke of the piston rod of the second-stage oil cylinder; when the first extending proportional stroke is larger than the second extending proportional stroke and the exceeding value is not smaller than the set threshold value, the first oil way is controlled to be conducted, so that the first-stage oil cylinder executes slight extending stopping operation; and when the second extending proportional stroke is larger than the first extending proportional stroke and the exceeding value is not smaller than the set threshold value, the second oil way is controlled to be conducted, so that the second-stage oil cylinder executes the slight extending stopping operation. According to the method, oil can be supplemented to the two oil cylinders at any extending positions in the process that the system executes the oil cylinder extending operation, so that the purpose of stroke compensation is achieved.

Description

Technical Field

[0001] This invention belongs to the field of work machinery technology, specifically relating to a series hydraulic cylinder system and its oil replenishment control method, and work machinery. Background Technology

[0002] In hydraulic transmission systems, tandem cylinders are widely used in small cranes, aerial work platforms, and other work machinery due to their compact structure and long stroke.

[0003] The core working principle of a tandem hydraulic cylinder is as follows: when pressurized oil enters the rodless chamber of the first-stage cylinder and pushes the piston rod of the first-stage cylinder to extend, the oil discharged from its rod chamber simultaneously enters the rodless chamber of the second-stage cylinder, driving the second-stage cylinder to extend as well. Ideally, through precise area matching, the two-stage cylinders can achieve stroke synchronization. That is, when one cylinder is fully extended or retracted, the other cylinder also reaches its corresponding limit position.

[0004] However, in actual operation, due to factors such as seal wear and oil temperature changes, leakage inevitably occurs inside the cylinder, causing a gradual difference in the stroke of the two cylinders and disrupting the original synchronization. To address this problem, existing technologies typically add a bypass oil supply circuit between the pressure oil circuit and the linkage oil circuit. However, this bypass oil supply circuit can only be activated actively or passively to supply oil when a certain stage cylinder reaches its fully extended or retracted limit position. When the tandem cylinders are working in the middle stroke, the bypass oil supply circuit cannot be triggered, resulting in a loss of stroke control accuracy. Furthermore, the existing oil supply method is essentially a reactive remedial mode, supplying oil only after the cylinder has reached its limit position, which can easily cause hydraulic shock. Summary of the Invention

[0005] To address the aforementioned deficiencies or shortcomings, this invention provides a tandem hydraulic cylinder system and its oil replenishment control method, as well as a working machine, aiming to solve the technical problem that existing oil replenishment methods for tandem cylinders cannot meet the system's requirements for high precision and high stability motion under complex working conditions.

[0006] To achieve the above objectives, on the one hand, the present invention provides a method for replenishing oil control in a series hydraulic cylinder system. The series hydraulic cylinder system includes a primary cylinder and a secondary cylinder. The rod chamber of the primary cylinder is connected to the rodless chamber of the secondary cylinder. A first oil circuit with on / off control is provided between the rod chamber and the rodless chamber of the primary cylinder, and a second oil circuit with on / off control is provided between the rod chamber and the rodless chamber of the secondary cylinder. The oil replenishing control method includes: When the tandem cylinder hydraulic system performs the cylinder extension operation, it detects and determines whether the first-stage cylinder and the second-stage cylinder extend synchronously. If the piston rods extend out of sync, compare the first proportional stroke of the piston rod of the first-stage cylinder with the second proportional stroke of the piston rod of the second-stage cylinder. When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than the set threshold, the first oil circuit is controlled to be opened so that the first-stage oil cylinder performs a slight pause extension operation. When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than the set threshold, the second oil circuit is controlled to be opened so that the second-stage oil cylinder performs a slight pause extension operation.

[0007] In this embodiment, after controlling the first oil circuit to open so that the first-stage oil cylinder performs a brief pause and extension operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue performing the cylinder extension operation; During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the first oil circuit is controlled to be cut off.

[0008] In this embodiment, after controlling the second oil circuit to activate so that the secondary oil cylinder performs a brief pause and extension operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue performing the cylinder extension operation; During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the second oil circuit is controlled to be cut off.

[0009] In this embodiment, the oil replenishment control method further includes: When the tandem cylinder hydraulic system performs a retraction operation, it is detected whether the first-stage cylinder and the second-stage cylinder retract synchronously. If the retraction is not synchronized, compare the magnitude of the first proportional stroke of the piston rod of the first-stage cylinder with the second proportional stroke of the piston rod of the second-stage cylinder. When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than the set threshold, the second oil circuit is controlled to be opened so that the second-stage oil cylinder performs a slight pause and retraction operation. When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than the set threshold, the first oil circuit is controlled to be turned on so that the first-stage oil cylinder performs a slight pause and retraction operation.

[0010] In this embodiment, after controlling the second oil circuit to activate so that the secondary oil cylinder performs a slight pause and retraction operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue executing the cylinder retraction operation; During the continued retraction of the hydraulic cylinder, if the absolute value of the difference between the first and second proportional extension strokes is less than a set threshold, the second hydraulic circuit is controlled to shut off.

[0011] In this embodiment, after controlling the first oil circuit to open so that the first-stage oil cylinder performs a slight pause and retraction operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue executing the cylinder retraction operation; During the continued execution of the cylinder retraction operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the first oil circuit is controlled to be cut off.

[0012] To achieve the above objectives, the present invention also provides a series cylinder hydraulic system, comprising a series cylinder assembly, a first working oil circuit, a second working oil circuit, and a controller. The series cylinder assembly includes a primary cylinder and a secondary cylinder. A linkage oil circuit is provided between the rod-side chamber of the primary cylinder and the rodless chamber of the secondary cylinder. A first oil circuit is provided between the rod-side and rodless chambers of the primary cylinder, and a first replenishing valve is provided on the first oil circuit. A second oil circuit is provided between the rod-side and rodless chambers of the secondary cylinder, and a second replenishing valve is provided on the second oil circuit. The first working oil circuit is connected to the rodless chamber of the primary cylinder, and the second working oil circuit is connected to the rod-side chamber of the secondary cylinder. The controller is electrically connected to the first and second replenishing valves and is used to execute the replenishing control method described above.

[0013] In this embodiment, the tandem cylinder hydraulic system further includes a distance detection component, which is used to detect the extension ratio of the piston rod of the first-stage cylinder and the piston rod of the second-stage cylinder.

[0014] In this embodiment, a balance valve assembly is provided between the linkage oil circuit and the second working oil circuit, and / or between the first working oil circuit and the second working oil circuit.

[0015] To achieve the above objectives, the present invention also provides a working machine, wherein the working machine includes a tandem hydraulic system of cylinders as described above.

[0016] Through the above technical solution, the oil replenishment control method for the tandem cylinder hydraulic system provided in this embodiment of the invention has the following beneficial effects: This method enables the replenishment of oil to both cylinders at any extension position and under any circumstances during the system's cylinder extension operation, achieving stroke compensation and overcoming the response lag and applicability limitations of traditional methods that only replenish oil at extreme positions. The dynamic oil replenishment mechanism in this method not only significantly improves the synchronization accuracy and stability of the two-stage cylinders during extension but also enhances the system's adaptability, making it particularly suitable for applications requiring long-term operation in the middle stroke or frequent start-stop cycles, thus improving the overall control performance and reliability of the system.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating the steps of the oil replenishment control method for the tandem hydraulic system of the present invention when performing the cylinder extension operation. Figure 2 This is a step diagram following step S300A in an embodiment of the present invention; Figure 3 This is a step diagram following step S300B in an embodiment of the present invention; Figure 4 This is a flowchart illustrating the steps of the oil replenishment control method for the tandem hydraulic system of the present invention when performing a cylinder retraction operation. Figure 5 This is a step diagram following step D300A in an embodiment of the present invention; Figure 6 This is a step diagram following step D300B in an embodiment of the present invention; Figure 7 This is a hydraulic schematic diagram of the tandem hydraulic system of the hydraulic cylinders according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures 1. First-stage hydraulic cylinder; 1a. First hydraulic circuit; 1b. First replenishing valve; 2. Second-stage hydraulic cylinder; 2a. Second hydraulic circuit; 2b. Second replenishing valve; 3. Linkage hydraulic circuit; 41. First working hydraulic circuit; 42. Second working hydraulic circuit; 51. First balance valve assembly; V1. First oil port on the oil source side; V2. Second oil port on the oil source side; C1. First oil port on the cylinder side; C2. Second oil port on the cylinder side; 52. Second balance valve assembly; V3. Third oil port; V4. Fourth oil port; C3. Fifth oil port; C4. Sixth oil port; 6. Distance detection component. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] The method for replenishing oil in the tandem hydraulic system of the present invention is described below with reference to the accompanying drawings.

[0022] Tandem cylinder systems are widely used in work machinery with relatively low load capacity requirements but strict space constraints due to their compact structure and ability to provide a long extension stroke. Examples include aerial work platforms and small truck-mounted cranes. These types of machinery typically need to achieve a large working radius or height variation within a limited installation space.

[0023] Currently, the oil replenishment triggering in tandem cylinder systems mainly occurs at the end of the cylinder's stroke. That is, when a cylinder moves to its fully extended or fully retracted mechanical limit position, the pressure change (or control signal) generated inside the system triggers the oil replenishment valve to open, thereby compensating for the volume difference caused by leakage in one go. This design has two inherent drawbacks: First, the compensation is severely delayed; the stroke difference accumulates throughout the entire working process and is only processed when the cylinder reaches its end point. If the cylinder works in the middle position for a long time, stroke correction cannot be performed. Second, the strokes of the tandem cylinders are inconsistent; it is possible that the first-stage cylinder extends slowly, or that the second-stage cylinder extends slowly. The existing oil replenishment method can only replenish oil in one of these situations.

[0024] In view of this, such as Figure 7 As shown, the present invention provides a series hydraulic cylinder system and its oil replenishment control method. The series hydraulic cylinder system includes a series hydraulic cylinder assembly as a drive mechanism. The series hydraulic cylinder assembly includes a primary cylinder 1 and a secondary cylinder 2. The rod chamber of the primary cylinder 1 is connected to the rodless chamber of the secondary cylinder 2. A first oil passage 1a that can be controlled to be switched on and off is provided between the rod chamber and the rodless chamber of the primary cylinder 1, and a second oil passage 2a that can be controlled to be switched on and off is provided between the rod chamber and the rodless chamber of the secondary cylinder 2.

[0025] Based on the above-mentioned tandem hydraulic cylinder system, such as Figure 1 As shown, the present invention also provides a system for oil replenishment control, the method comprising: S100: When the hydraulic system of tandem cylinders performs the cylinder extension operation, it detects and determines whether the first-stage cylinder 1 and the second-stage cylinder 2 extend synchronously. S200: If the extensions are not synchronized, compare the first proportional stroke of the piston rod of the first-stage cylinder 1 with the second proportional stroke of the piston rod of the second-stage cylinder 2. S300A: When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than the set threshold, control the first oil circuit 1a to be turned on so that the first stage oil cylinder 1 performs a slight pause extension operation. S300B: When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than the set threshold, the second oil circuit 2a is controlled to be turned on so that the second-stage oil cylinder 2 performs a slight pause extension operation.

[0026] When the tandem hydraulic system extends the cylinder, pressurized oil enters the rodless chamber of the first-stage cylinder 1 and pushes the piston rod of the first-stage cylinder 1 to extend. The oil discharged from the rod chamber of the first-stage cylinder 1 enters the rodless chamber of the second-stage cylinder 2 simultaneously and drives the second-stage cylinder to extend. At this time, the rod chamber of the second-stage cylinder 2 is the oil unloading side.

[0027] This method detects the first proportional stroke of the piston rod of the first-stage cylinder 1 and the second proportional stroke of the piston rod of the second-stage cylinder 2 during the extension of the tandem cylinder assembly. The magnitudes of these two proportional strokes are compared to determine if the two cylinders are extending asynchronously. If the absolute value of the difference between the first and second proportional strokes is less than a set threshold, it indicates that their strokes are synchronized, or even if asynchrony occurs, the degree of asynchrony is within the system's tolerance range. If the absolute value of the difference between the first and second proportional strokes is greater than the set threshold, it indicates that the two cylinders are extending asynchronously, and the degree of asynchrony will affect the stable operation and normal functioning of the system. In this case, a replenishment oil operation can be performed. During extension, it is possible for the first-stage cylinder 1 to extend faster than the second-stage cylinder 2, or vice versa. The replenishment oil operation will vary slightly depending on the specific situation.

[0028] When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is greater than or equal to the set threshold, it indicates that the extension of the secondary cylinder 2 is too slow and the stroke difference exceeds the system's fault tolerance range. At this time, by controlling the first oil circuit 1a to open, the hydraulic oil flowing from the pressure oil circuit into the rodless chamber of the primary cylinder 1 can flow directly into the rod chamber of the primary cylinder 1 and the rodless chamber of the secondary cylinder 2 through the first oil circuit 1a. The pressure in the rod and rodless chambers of the primary cylinder 1 becomes equal, the primary cylinder 1 pauses slightly, and the secondary cylinder 2 extends independently. By controlling the primary cylinder 1 to pause slightly and the secondary cylinder 2 to extend independently, the extension proportional stroke of the secondary cylinder 2 can be controlled to catch up with that of the primary cylinder 1, thereby restoring the synchronization of the strokes of the primary cylinder 1 and the secondary cylinder 2.

[0029] When the second proportional stroke of the extension exceeds the first proportional stroke and the excess value is greater than or equal to the set threshold, it indicates that the extension of the first-stage cylinder 1 is too slow and the stroke difference exceeds the system's fault tolerance range. In this case, by controlling the second oil circuit 2a to open, the hydraulic oil flowing from the rod chamber of the first-stage cylinder 1 and into the rodless chamber of the second-stage cylinder 2 can continue to flow directly to the rod chamber of the second-stage cylinder 2 through the second oil circuit 2a, thereby unloading the oil. In this situation, oil enters the rodless chamber of the first-stage cylinder 1, the first-stage cylinder 1 extends, and the second-stage cylinder 2 pauses slightly. By controlling the second-stage cylinder 2 to pause slightly and the first-stage cylinder 1 to extend independently, the proportional stroke of the extension of the first-stage cylinder 1 can be controlled to catch up with that of the second-stage cylinder 2, thus restoring the synchronization of the strokes of the first-stage cylinder 1 and the second-stage cylinder 2.

[0030] In summary, this method can replenish oil to both cylinders at any extension position and under any circumstances during the system's cylinder extension operation, achieving stroke compensation and overcoming the response lag and applicability limitations of traditional methods that only replenish oil at extreme positions. The dynamic oil replenishment mechanism in this method not only significantly improves the synchronization accuracy and stability of the two-stage cylinders during extension but also enhances the system's adaptability, making it particularly suitable for applications requiring long-term operation in the middle stroke or frequent start-stop cycles, thus improving the overall control performance and reliability of the system.

[0031] It is understood that the extension ratio stroke in this embodiment refers to the percentage of the cylinder's extension length converted to its maximum stroke. For example, when the extension ratio stroke of the first-stage cylinder 1 is 0%, it means that the first-stage cylinder 1 is in a fully retracted state; when the extension ratio stroke of the first-stage cylinder 1 is 100%, it means that the first-stage cylinder 1 is in a fully extended state. Ideally, the extension ratio stroke of the first-stage cylinder 1 should be consistent with the extension ratio stroke of the second-stage cylinder 2.

[0032] like Figure 2 and Figure 7 As shown, in this embodiment, in step S300A, after controlling the first oil circuit 1a to be turned on so that the first-stage oil cylinder 1 performs a slight pause extension operation, the oil replenishment control method further includes: S400A: Controls the tandem cylinder hydraulic system to continue performing the cylinder extension operation; S500A: During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the first oil circuit 1a is controlled to be cut off.

[0033] After the first oil circuit 1a is opened, the control pressure oil circuit continues to supply oil to the rodless chamber of the first-stage cylinder 1. At this time, the first-stage cylinder 1 pauses slightly, and the second-stage cylinder 2 extends independently. The extension proportional stroke of the first-stage cylinder 1 and the second-stage cylinder 2 is monitored. When the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, it indicates that the stroke synchronization of the first-stage cylinder 1 and the second-stage cylinder 2 has been restored to the fault tolerance range of the system. At this time, the first oil circuit 1a can be disconnected to restore the synchronous movement of the two cylinders.

[0034] Similarly, as Figure 3 and Figure 7 As shown, in step S300B, after controlling the second oil circuit 2a to be turned on so that the secondary oil cylinder 2 performs a slight pause extension operation, the oil replenishment control method further includes: S400B: Controls the tandem cylinder hydraulic system to continue performing the cylinder extension operation; S500B: During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, the second oil circuit 2a is controlled to be cut off.

[0035] When the second oil circuit 2a is activated, the control pressure oil circuit continues to supply oil to the rodless chamber of the first-stage cylinder 1. At this time, the second-stage cylinder 2 pauses slightly, and the first-stage cylinder 1 extends independently. The extension proportional stroke of the first-stage cylinder 1 and the second-stage cylinder 2 is monitored. When the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, it indicates that the stroke synchronization of the first-stage cylinder 1 and the second-stage cylinder 2 has been restored to the system's fault tolerance range. At this time, the second oil circuit 2a can be disconnected to restore the synchronous movement of the two cylinders.

[0036] like Figure 4 and Figure 7 As shown, in this embodiment, the oil replenishment control method further includes: D100: When the tandem cylinder hydraulic system performs a retraction operation, it detects whether the first-stage cylinder 1 and the second-stage cylinder 2 retract synchronously. D200: If the retraction is not synchronized, compare the first extension proportional stroke of the piston rod of the first stage cylinder 1 with the second extension proportional stroke of the piston rod of the second stage cylinder 2. D300A: When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than the set threshold, control the second oil circuit 2a to be turned on so that the second-stage oil cylinder 2 performs a slight pause and retraction operation. D400A: When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than the set threshold, the first oil circuit 1a is controlled to be turned on so that the first stage oil cylinder 1 performs a slight pause and retraction operation.

[0037] When the tandem hydraulic system performs the cylinder retraction operation, pressurized oil enters the rod chamber of the secondary cylinder 2 and pushes the piston rod of the secondary cylinder 2 to retract. The oil discharged from the rodless chamber of the secondary cylinder 2 will simultaneously enter the rod chamber of the primary cylinder 1 and drive the primary cylinder to retract. At this time, the rodless chamber of the primary cylinder 1 is the oil unloading side.

[0038] During the retraction of the tandem cylinder assembly, if the first extension proportional stroke exceeds the second extension proportional stroke and the excess value is greater than or equal to a set threshold, it indicates that the retraction of the first-stage cylinder 1 is too slow, and the stroke difference between the two cylinders exceeds the system's fault tolerance range. At this point, by controlling the second oil circuit 2a to open, the hydraulic oil flowing from the pressure oil circuit into the rod-side chamber of the second-stage cylinder 2 can directly enter the rodless chamber of the second-stage cylinder 2 and the rod-side chamber of the first-stage cylinder 1 through the second oil circuit 2a. At this time, the second-stage cylinder 2 pauses slightly, and the first-stage cylinder 1 retracts independently. By controlling the second-stage cylinder 2 to pause slightly and the first-stage cylinder 1 to retract independently, the extension proportional stroke of the first-stage cylinder 1 can be reduced to be synchronized with that of the second-stage cylinder 2.

[0039] When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is greater than or equal to the set threshold, it indicates that the retraction of the secondary cylinder 2 is too slow, and the stroke difference between the two cylinders exceeds the system's fault tolerance range. In this case, by controlling the first oil circuit 1a to open, the hydraulic oil flowing from the rodless chamber of the secondary cylinder 2 into the rod chamber of the primary cylinder 1 can flow through the first oil circuit 1a back to the rodless chamber of the primary cylinder 1, thereby unloading the oil. In this situation, the primary cylinder 1 pauses slightly, and the secondary cylinder 2 retracts independently. By controlling the primary cylinder 1 to pause slightly and the secondary cylinder 2 to retract independently, the extension proportional stroke of the secondary cylinder 2 can be reduced to be synchronized with that of the primary cylinder 1.

[0040] In other words, this method not only replenishes oil to the two cylinders during the extension operation, but also replenishes oil during the retraction operation. By detecting and dynamically replenishing oil throughout the stroke of the tandem cylinder assembly, the system's adaptability to different working conditions is increased.

[0041] like Figure 5 and Figure 7 As shown, in this embodiment, step D300A: controlling the second oil circuit 2a to be turned on so that the secondary oil cylinder 2 performs a slight pause and retraction operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue executing the cylinder retraction operation; During the continued execution of the cylinder retraction operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the second oil circuit 2a is controlled to be cut off.

[0042] After the second oil circuit 2a is opened, the control pressure oil circuit continues to supply oil to the rod chamber of the second-stage cylinder 2. At this time, the second-stage cylinder 2 pauses slightly, and the first-stage cylinder 1 retracts independently. The extension proportional stroke of the first-stage cylinder 1 and the second-stage cylinder 2 is monitored. When the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, it indicates that the stroke synchronization of the first-stage cylinder 1 and the second-stage cylinder 2 has been restored to the fault tolerance range of the system. At this time, the second oil circuit 2a can be disconnected to restore the synchronous movement of the two cylinders.

[0043] like Figure 6 and Figure 7 As shown, in this embodiment, step D300B: controlling the first oil circuit 1a to be turned on so that the first-stage oil cylinder 1 performs a slight pause and retraction operation, the oil replenishment control method further includes: Control the tandem hydraulic system to continue executing the cylinder retraction operation; During the continued execution of the cylinder retraction operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than a set threshold, the first oil circuit 1a is controlled to be cut off.

[0044] After the first oil circuit 1a is opened, the control pressure oil circuit continues to supply oil to the rod chamber of the second-stage cylinder 2. At this time, the first-stage cylinder 1 pauses slightly, and the second-stage cylinder 2 retracts independently. The extension proportional stroke of the first-stage cylinder 1 and the second-stage cylinder 2 is monitored. When the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, it indicates that the stroke synchronization of the first-stage cylinder 1 and the second-stage cylinder 2 has been restored to the system's fault tolerance range. At this time, the first oil circuit 1a can be disconnected to restore the synchronous movement of the two cylinders.

[0045] like Figure 7 As shown, in this embodiment, a first replenishing valve 1b for controlling the on / off state is provided on the first oil circuit 1a, and a second replenishing valve 2b for controlling the on / off state is provided on the second oil circuit 2a. The series hydraulic cylinder system also includes a controller, which is electrically connected to both the first replenishing valve 1b and the second replenishing valve 2b and is used to execute the replenishing control method described above. The replenishing valve can be a switching valve or other types of directional valves. By switching the valve position of the corresponding replenishing valve, the on / off state of the first oil circuit 1a and the second oil circuit 2a can be controlled.

[0046] like Figure 7 As shown, in this embodiment, the tandem cylinder hydraulic system further includes a first working oil circuit 41 and a second working oil circuit 42. The first working oil circuit 41 is connected to the rodless chamber of the first-stage cylinder 1, and the second working oil circuit 42 is connected to the rod chamber of the second-stage cylinder 2. When the system performs a cylinder extension operation, oil enters the first working oil circuit 41 and returns oil to the second working oil circuit 42; when the system performs a cylinder retraction operation, oil enters the second working oil circuit 42 and returns oil to the first working oil circuit 41.

[0047] like Figure 7 As shown, in this embodiment, the tandem cylinder hydraulic system further includes a distance detection component 6. The distance detection component 6 is used to detect the extension proportional stroke of the piston rod of the first-stage cylinder 1 and the piston rod of the second-stage cylinder 2. The distance detection component 6 can be a distance sensor, a displacement sensor, a laser rangefinder, or other devices. Through the distance detection component 6, the first extension proportional stroke of the piston rod of the first-stage cylinder 1 and the second extension proportional stroke of the piston rod of the second-stage cylinder 2 can be detected.

[0048] like Figure 7 As shown, in this embodiment, a balance valve group is provided between the linkage oil circuit 3 and the second working oil circuit 42, and / or between the first working oil circuit 41 and the second working oil circuit 42.

[0049] Specifically, a first balance valve assembly 51 is provided between the first working oil circuit 41 and the second working oil circuit 42. The first balance valve assembly 51 has a first oil port V1 on the oil source side, a second oil port V2 on the oil source side, a first oil port C1 on the cylinder side, and a second oil port C2 on the cylinder side. A first balance oil passage and a first one-way oil passage are provided in parallel between the first oil port V1 on the oil source side and the first oil port C1 on the cylinder side. The first balance oil passage and the first one-way oil passage form part of the first working oil circuit 41. A first balance valve is provided on the first balance oil passage. A second balance oil passage and a second one-way oil passage are provided in parallel on the second working oil circuit 42 between the second oil port V2 and the second oil port C2 on the cylinder side. The second balance oil passage and the second one-way oil passage form part of the second working oil circuit 42. A second balance valve is provided on the second one-way oil passage. The pilot side of the first balance valve is connected to the second oil port V2 on the oil source side, and the pilot side of the second balance valve is connected to the first oil port V1 on the oil source side. The first one-way passage and the second one-way passage are configured to allow hydraulic oil to flow only from the oil port on the oil source side to the oil port on the cylinder side.

[0050] By means of the first balance valve group 51, stable pressure can be maintained in the rodless chamber of the first-stage cylinder 1 and the rod chamber of the second-stage cylinder 2 when the series cylinder assembly stops operating.

[0051] In this embodiment, a second balance valve assembly 52 is provided between the linkage oil circuit 3 and the second working oil circuit 42. The second balance valve assembly 52 includes a third oil port V3, a fourth oil port V4, a fifth oil port C3, and a sixth oil port C4. A third balance oil passage and a third one-way oil passage are provided between the third oil port V3 and the fifth oil port C3, and a fourth balance oil passage is provided between the fourth oil port V4 and the sixth oil port C4. The third balance passage and the third one-way oil passage form part of the linkage oil circuit 3. A third balance valve is provided on the third balance oil passage, and the pilot side of the third balance valve is connected to the fourth balance oil passage. The third one-way oil passage is configured to allow hydraulic oil to flow only from the rod chamber of the first-stage cylinder 1 to the rodless chamber of the second-stage cylinder 2. Since the second balance passage has already balanced the rod chamber of the second-stage cylinder 2, there is no need to provide a balance valve and a one-way oil passage on the fourth balance passage.

[0052] The second balance valve group 52 is used to isolate the rod chamber of the first-stage cylinder 1 from the rodless chamber of the second-stage cylinder 2 when the series cylinder assembly stops operating.

[0053] To achieve the above objectives, the present invention also provides a working machine, wherein the working machine includes a tandem hydraulic system of cylinders as described above. Since the working machine adopts all the technical solutions of the above embodiments, it at least possesses the beneficial effects brought about by the above embodiments, and will not be repeated here.

[0054] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0056] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0057] Although embodiments of the present invention have been described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for replenishing oil control in a tandem hydraulic cylinder system, characterized in that, The tandem hydraulic system includes a primary cylinder (1) and a secondary cylinder (2). The rod chamber of the primary cylinder (1) is connected to the rodless chamber of the secondary cylinder (2). A first oil circuit (1a) with on / off control is provided between the rod chamber and the rodless chamber of the primary cylinder (1), and a second oil circuit (2a) with on / off control is provided between the rod chamber and the rodless chamber of the secondary cylinder (2). The oil replenishment control method includes: When the tandem hydraulic system performs the cylinder extension operation, it detects and determines whether the first-stage cylinder (1) and the second-stage cylinder (2) extend synchronously. If the extensions are not synchronized, the first extension proportional stroke of the piston rod of the first-stage cylinder (1) is compared with the second extension proportional stroke of the piston rod of the second-stage cylinder (2); When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than a set threshold, the first oil circuit (1a) is controlled to be turned on so that the first-stage oil cylinder (1) performs a slight pause extension operation; When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than a set threshold, the second oil circuit (2a) is controlled to be turned on so that the secondary oil cylinder (2) performs a slight pause extension operation.

2. The oil replenishment control method for a tandem cylinder hydraulic system according to claim 1, characterized in that, After controlling the first oil circuit (1a) to be turned on so that the first-stage oil cylinder (1) performs a brief pause extension operation, the oil replenishment control method further includes: The hydraulic system of the tandem cylinders is controlled to continue performing the cylinder extension operation; During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, the first oil circuit (1a) is controlled to be cut off.

3. The oil replenishment control method for a tandem cylinder hydraulic system according to claim 1, characterized in that, After controlling the second oil circuit (2a) to open so that the secondary oil cylinder (2) performs a brief pause extension operation, the oil replenishment control method further includes: The hydraulic system of the tandem cylinders is controlled to continue performing the cylinder extension operation; During the continued execution of the cylinder extension operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, the second oil circuit (2a) is controlled to be cut off.

4. The oil replenishment control method for a tandem hydraulic system according to claim 1, characterized in that, The oil replenishment control method also includes: When the tandem hydraulic system performs a retraction operation, it is detected whether the first-stage cylinder (1) and the second-stage cylinder (2) retract synchronously. If the retraction is not synchronized, then compare the first extension proportional stroke of the piston rod of the first-stage cylinder (1) with the second extension proportional stroke of the piston rod of the second-stage cylinder (2); When the first extension proportional stroke is greater than the second extension proportional stroke and the excess value is not less than a set threshold, the second oil circuit (2a) is controlled to be turned on so that the secondary oil cylinder (2) performs a slight pause retraction operation; When the second extension proportional stroke is greater than the first extension proportional stroke and the excess value is not less than a set threshold, the first oil circuit (1a) is controlled to be turned on so that the first-stage oil cylinder (1) performs a slight pause retraction operation.

5. The oil replenishment control method for a tandem cylinder hydraulic system according to claim 4, characterized in that, After controlling the second oil circuit (2a) to be turned on so that the secondary oil cylinder (2) performs a slight pause and retraction operation, the oil replenishment control method further includes: The hydraulic system of the tandem cylinders is controlled to continue performing the cylinder retraction operation; During the continued execution of the cylinder retraction operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, the second oil circuit (2a) is controlled to be cut off.

6. The oil replenishment control method for a tandem cylinder hydraulic system according to claim 4, characterized in that, After controlling the first oil circuit (1a) to be turned on so that the first-stage oil cylinder (1) performs a slight pause and retraction operation, the oil replenishment control method further includes: The hydraulic system of the tandem cylinders is controlled to continue performing the cylinder retraction operation; During the continued execution of the cylinder retraction operation, if the absolute value of the difference between the first extension proportional stroke and the second extension proportional stroke is less than the set threshold, the first oil circuit (1a) is controlled to be cut off.

7. A tandem hydraulic cylinder system, characterized in that, The tandem cylinder hydraulic system includes: A series hydraulic cylinder assembly includes a primary hydraulic cylinder (1) and a secondary hydraulic cylinder (2). A linkage oil passage (3) is provided between the rod chamber of the primary hydraulic cylinder (1) and the rodless chamber of the secondary hydraulic cylinder (2). A first oil passage (1a) is provided between the rod chamber and the rodless chamber of the primary hydraulic cylinder (1). A first oil replenishment valve (1b) is provided on the first oil passage (1a). A second oil passage (2a) is provided between the rod chamber and the rodless chamber of the secondary hydraulic cylinder (2). A second oil replenishment valve (2b) is provided on the second oil passage (2a). The first working oil circuit (41) is connected to the rodless chamber of the first-stage oil cylinder (1); The second working oil circuit (42) is connected to the rod chamber of the secondary oil cylinder (2); The controller is electrically connected to the first replenishing valve (1b) and the second replenishing valve (2b) and is used to perform the replenishing control method according to any one of claims 1 to 6.

8. The tandem hydraulic system of cylinders according to claim 7, characterized in that, The tandem cylinder hydraulic system also includes a distance detection component (6), which is used to detect the extension ratio of the piston rod of the first-stage cylinder (1) and the piston rod of the second-stage cylinder (2).

9. The tandem hydraulic system of cylinders according to claim 7, characterized in that, A balance valve assembly is provided between the linkage oil circuit (3) and the second working oil circuit (42), and / or between the first working oil circuit (41) and the second working oil circuit (42).

10. A type of operating machinery, characterized in that, Includes the tandem hydraulic system of cylinders according to any one of claims 7 to 9.

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