Serial oil cylinder synchronous hydraulic system, synchronization method and telescopic boom forklift loader

Abstract

The invention discloses a series oil cylinder synchronous hydraulic system, a synchronization method and a telescopic boom forklift loader. The series oil cylinder synchronous hydraulic system comprises a first oil cylinder, a second oil cylinder, an electromagnetic valve and a hydraulic oil tank; the first connector is connected with a small cavity of the first oil cylinder and a large cavity of the second oil cylinder, the second connector is connected with the small cavity of the first oil cylinder and the large cavity of the second oil cylinder, the third connector is connected with the hydraulic oil tank, and the fourth connector is connected with the hydraulic oil tank. When the electromagnetic valve is powered on, the third connector is communicated with the first connector, the second connector is connected with the fourth connector, and gas in the small cavity of the first oil cylinder and gas in the large cavity of the second oil cylinder enter the hydraulic oil tank sequentially through the second connector and the fourth connector. The invention relates to a series oil cylinder synchronous hydraulic system, which solves the problem that the existing series oil cylinders are asynchronous, and particularly solves the problem that the series oil cylinders are asynchronous due to air in guide pipes when the series oil cylinders are injected with oil for the first time or after the series oil cylinders are repaired and maintained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil cylinder control, and particularly relates to a series connection oil cylinder synchronous hydraulic system, a synchronous method and a telescopic handler. BACKGROUND

[0002] In engineering machinery such as telescopic handlers, container front loaders and the like, two or more hydraulic oil cylinders are commonly used to drive the same working mechanism in series connection to realize telescopic or lifting actions with large strokes and high loads. The synchronization accuracy of the motion of the multiple oil cylinders is extremely demanding in such applications, and slight asynchronization may cause additional stress on structural members, unstable motion, accelerated sealing wear, and even safety accidents.

[0003] However, after the hydraulic system is put on the ground (initial oil filling) or maintained (replacement of oil cylinders, pipelines, valve parts and the like), air is inevitably mixed into the oil circuit and the oil cylinder cavities. The high compressibility and low rigidity of the air are key causes of the asynchronization of the motion of the series connection oil cylinders.

[0004] At present, maintenance personnel or commissioning personnel commonly rely on tedious manual operations (such as repeated point operation of the oil cylinders and operation of the air release screw) to discharge the air in the system. Such a method at least has the following disadvantages: (1) Low efficiency and time and labor consuming: the manual air release process is lengthy, which seriously affects the equipment delivery efficiency and maintenance progress; (2) Unreliable air release effect: limited by the skills and patience of the operators, the air in the complex pipelines and multiple oil cylinder cavities is difficult to completely discharge, and the residual air becomes a hidden danger of the asynchronization; (3) Lack of automatic protection: the existing system does not have the capability of automatic detection and air discharge, and the operator cannot predict whether the air is completely discharged when the equipment is started for the first time or after maintenance, and there is a risk of directly putting into work due to the asynchronization caused by the air; (4) Poor synchronization protection: the residual air is extremely likely to cause significant asynchronization of the oil cylinders when the equipment is first operated with a load, which may cause action shaking, precision reduction, accelerated component damage or even structural damage.

[0005] There is an urgent need for a technical solution capable of automatically, efficiently and reliably discharging the air in the series connection oil cylinder hydraulic system after the equipment is put on the ground or maintained, so as to fundamentally eliminate the adverse effects of the air on the synchronization of the oil cylinders and protect the safety, stability and reliability of the equipment operation. SUMMARY

[0006] One of the purposes of the application is to disclose a series connection oil cylinder synchronous hydraulic system, which solves the problem of asynchronization of the existing series connection oil cylinders, and specifically eliminates the problem of asynchronization of the series connection oil cylinders caused by the air in the guide pipe when the series connection oil cylinders are initially filled with oil or after maintenance.

[0007] The second object of the present application is to disclose a series oil cylinder synchronization method, which is synchronized by the series oil cylinder synchronization hydraulic system, and is convenient and fast to control and has good control effect.

[0008] The third object of the present application is to disclose a telescopic handler, which uses the series oil cylinder synchronization hydraulic system, and can ensure the synchronization of the series oil cylinder and the normal and efficient operation of the machine.

[0009] In order to achieve the above object, the present application discloses a series oil cylinder synchronization hydraulic system, which comprises a first oil cylinder, a second oil cylinder, an electromagnetic valve and a hydraulic oil tank, wherein the electromagnetic valve has a first interface, a second interface, a third interface and a fourth interface. The first interface is connected with the small cavity of the first oil cylinder and the large cavity of the second oil cylinder, the second interface is connected with the small cavity of the first oil cylinder and the large cavity of the second oil cylinder, the third interface is connected with the hydraulic oil tank, and the fourth interface is connected with the hydraulic oil tank. When the electromagnetic valve is powered, the third interface is communicated with the first interface, and the hydraulic oil in the hydraulic oil tank enters the small cavity of the first oil cylinder and the large cavity of the second oil cylinder through the third interface and the first interface in sequence; when the electromagnetic valve is powered, the second interface and the fourth interface are connected, and the gas in the small cavity of the first oil cylinder and the large cavity of the second oil cylinder enters the hydraulic oil tank through the second interface and the fourth interface in sequence.

[0010] As an optional embodiment, the series oil cylinder synchronization hydraulic system further comprises an oil return check valve, which is arranged between the fourth interface of the electromagnetic valve and the hydraulic oil tank, and the oil return check valve guides the oil path from the fourth interface to the hydraulic oil tank.

[0011] As an optional embodiment, the series oil cylinder synchronization hydraulic system further comprises a working pump, the outlet of the working pump is communicated with the third interface of the electromagnetic valve, and the inlet of the working pump is connected with the hydraulic oil tank.

[0012] As an optional embodiment, the series oil cylinder synchronization hydraulic system further comprises a main control valve, which comprises a first oil port, a second oil port, a third oil port and a fourth oil port. The first oil port is connected with the large cavity of the first oil tank, the second oil port is connected with the small cavity of the second oil cylinder, the third oil port is connected with the hydraulic oil tank, and the fourth oil port is connected with the outlet of the working pump. When the main control valve is in the first working position, the first oil port is communicated with the fourth oil port, and the second oil port is communicated with the third oil port. When the master valve is in the second working position, the second oil port is communicated with the fourth oil port, and the first oil port is communicated with the third oil port.

[0013] As an optional embodiment, the series oil cylinder synchronization hydraulic system further comprises a first balance valve; The first balance valve has a first valve port, a second valve port, a third valve port and a fourth valve port; The third valve port is communicated with the first valve port through a first one-way valve, and the fourth valve port is communicated with the second valve port through a second one-way valve; A first pilot valve is connected between the third valve port and the first valve port, and a pilot port of the first pilot valve is communicated with the fourth valve port; A second pilot valve is connected between the fourth valve port and the second valve port, and a pilot port of the second pilot valve is communicated with the third valve port; The first valve port is connected with a large cavity of the first oil cylinder, the second valve port is connected with a small cavity of the second oil cylinder, the third valve port is connected with a first oil port of the master valve, and the fourth valve port is connected with a second oil port of the master valve.

[0014] As an optional embodiment, the series oil cylinder synchronization hydraulic system further comprises a second balance valve; The second balance valve has a valve port one, a valve port two, a valve port three and a valve port four; The valve port three is communicated with the valve port one through a one-way valve one, and the valve port four is directly communicated with the valve port two; A pilot valve one is connected between the valve port three and the valve port one, a pilot port of the pilot valve one is communicated with the valve port four, and a one-way valve two is arranged between the pilot port of the pilot valve one and the valve port four, which communicates an oil path from the valve port four to the pilot port of the pilot valve one.

[0015] As an optional embodiment, the first oil cylinder comprises a first oil cylinder push rod, and the second oil cylinder comprises a second oil cylinder push rod, and effective areas of the first oil cylinder push rod and the second oil cylinder push rod are adapted to each other.

[0016] A series oil cylinder synchronization method, which is controlled by the series oil cylinder synchronization hydraulic system described above; After the series oil cylinder synchronization hydraulic system is assembled, gas in the small cavity of the first oil cylinder and the large cavity of the second oil cylinder is discharged, and the method comprises the following steps: The electromagnetic valve is powered on, the working pump is started, the working pump outputs hydraulic oil, the hydraulic oil enters the electromagnetic valve through the third valve port of the electromagnetic valve, and then is output through the first valve port of the electromagnetic valve and enters the small cavity of the first oil cylinder and the large cavity of the second oil cylinder respectively, and the small cavity of the first oil cylinder and the large cavity of the second oil cylinder are filled respectively, and at the same time, the gas in the small cavity of the first oil cylinder and the gas in the large cavity of the second oil cylinder enter the electromagnetic valve through the second valve port of the electromagnetic valve, and finally are discharged to the hydraulic oil tank through the fourth valve port of the electromagnetic valve.

[0017] As an optional implementation, the series oil cylinder synchronization method further comprises controlling the first oil cylinder and the second oil cylinder to synchronously extend and retract during operation of the first oil cylinder and the second oil cylinder, and comprises the following steps: The electromagnetic valve is powered off, the main control valve is located at the first working position, the working pump outputs hydraulic oil to the main control valve, the main control valve delivers the hydraulic oil to the large cavity of the first oil cylinder through the first oil port and the first balance valve, the hydraulic oil in the large cavity of the first oil cylinder compresses the space of the small cavity of the first oil cylinder, the hydraulic oil in the small cavity of the first oil cylinder is output and enters the large cavity of the second oil cylinder through the second balance valve, and the first oil cylinder and the second oil cylinder synchronously extend. The electromagnetic valve is powered off, the main control valve is located at the second working position, the working pump outputs hydraulic oil to the main control valve, the main control valve delivers the hydraulic oil to the small cavity of the second oil cylinder through the second oil port and the second balance valve, the hydraulic oil in the small cavity of the second oil cylinder compresses the space of the large cavity of the second oil cylinder, the hydraulic oil in the large cavity of the second oil cylinder is output and enters the small cavity of the second oil cylinder through the second balance valve, and the first oil cylinder and the second oil cylinder synchronously retract.

[0018] A telescopic forklift truck comprises the series oil cylinder synchronization hydraulic system.

[0019] Compared with the prior art, the series oil cylinder synchronization hydraulic system has the following beneficial effects: 1. In the series oil cylinder system, the small cavity of the first oil cylinder is directly connected with the large cavity of the second oil cylinder, that is, the oil return cavity of the former oil cylinder drives the extension cavity of the latter oil cylinder, the connecting pipeline structure is complex and air is easy to accumulate, and the system can eliminate the problem of different movements of the oil cylinders caused by residual air by discharging the air in the pipeline of the series oil cylinder hydraulic system after the machine is placed on the ground or is maintained.

[0020] 2. In the hydraulic system, two independent paths are formed when the electromagnetic valve is powered on through directional control of the electromagnetic valve, manual intervention is not required, one-key starting can be realized, the air-accumulating cavity can be accurately covered, the air can be completely discharged, and the problem of air discharge at the series connection node which is difficult to handle in the traditional method is solved.

[0021] 3. After air discharge, the small cavity of the first oil cylinder and the large cavity of the second oil cylinder are filled with incompressible hydraulic oil, and the influence of the compressibility of the gas on the movement rigidity is eliminated.

[0022] 4. The hydraulic system only needs to add a two-position four-way electromagnetic valve, without additional sensors or complex control program, low cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings described in the following embodiments are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0024] Figure 1 is an embodiment diagram of a series oil cylinder synchronous hydraulic system of the present application.

[0025] Main figure mark explanation: 1, main control valve; 2, first balance valve; 3, first oil cylinder; 4, second oil cylinder; 5, second balance valve; 6, electromagnetic valve; 7, oil return check valve; 8, working pump; 9, hydraulic oil tank. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the scope of protection of the present application.

[0027] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "transverse", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0028] Moreover, in addition to being used to indicate the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific situation.

[0029] In addition, the terms "mounting", "arrangement", "provided with", "connected", "linked" should be interpreted broadly. For example, it can be fixed connection, detachable connection, or integral structure; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] In addition, the terms "first", "second" and the like are mainly used to distinguish different devices, elements or components (the specific type and structure can be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "multiple" is two or more.

[0031] The technical solutions of the present application will be further described below in conjunction with the embodiments and drawings.

[0032] Please refer to Figure 1 The embodiment of the present application provides a series oil cylinder synchronous hydraulic system.

[0033] A series oil cylinder synchronous hydraulic system, comprising a first oil cylinder 3, a second oil cylinder 4, a solenoid valve 6 and a hydraulic oil tank 9, the solenoid valve 6 has a first interface A, a second interface B, a third interface P and a fourth interface T.

[0034] The first interface A is connected with the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4, the second interface B is connected with the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4, the third interface P is connected with the hydraulic oil tank 9, and the fourth interface T is connected with the hydraulic oil tank 9.

[0035] When the solenoid valve 6 is powered, the third interface P is communicated with the first interface A, and the hydraulic oil in the hydraulic oil tank 9 enters the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 in turn through the third interface P and the first interface A. When the solenoid valve 6 is powered, the second interface B and the fourth interface T are connected, and the gas in the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 enters the hydraulic oil tank 9 in turn through the second interface B and the fourth interface T.

[0036] In the hydraulic system of the series oil cylinder, the small cavity of the first oil cylinder 3 is directly connected with the large cavity of the second oil cylinder 4, that is, the oil return cavity of the former oil cylinder drives the extension cavity of the latter oil cylinder, the connection pipeline structure between the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 is complex and air is easy to accumulate, the compressibility of the residual air causes the motion lag of the first oil cylinder 3 and / or the second oil cylinder 4, and the multi-stage oil cylinders are seriously out of synchronization under load. The series oil cylinder synchronization hydraulic system can automatically and efficiently discharge the air in the pipeline of the series oil cylinder hydraulic system after the whole machine is grounded or maintained, eliminate the problem of motion out of synchronization of the oil cylinder caused by the residual air, solve the problem of lack of synchronization of the multi-stage oil cylinders, and also solve the problem of low efficiency of the existing manual air discharge.

[0037] In the embodiment, when the electromagnetic valve 6 is powered, the third interface P is in communication with the first interface A, and the hydraulic oil in the hydraulic oil tank 9 enters the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 through the third interface P and the first interface A respectively. When the electromagnetic valve 6 is powered, the second interface B and the fourth interface T are connected, and the gas in the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 enters the hydraulic oil tank 9 through the second interface B and the fourth interface T in turn. That is, through the directional control of the electromagnetic valve 6, two independent paths, an oil injection path and an air discharge path, are formed when powered. The oil injection path actively injects the hydraulic oil in the hydraulic oil tank 9 into the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4, that is, actively injects the hydraulic oil in the hydraulic oil tank 9 into the key series connection node of the oil cylinder system which needs to be discharged, and realizes oil discharge. The air discharge path causes the gas in the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 to be squeezed out to the oil tank by the hydraulic oil. In the embodiment, without manual intervention, one-key starting can accurately cover the air-accumulating cavity, completely discharge the air, solve the problem of air discharge of the series connection node which is difficult to handle by the traditional method, and also solve the problem of low efficiency of the existing manual air discharge.

[0038] In the embodiment, the small cavity of the first oil cylinder 3 and the large cavity of the second oil cylinder 4 after air discharge are filled with incompressible hydraulic oil, eliminating the influence of gas compressibility on motion rigidity. The series oil cylinder is completely synchronized under load, avoiding the risk of arm frame torsional deformation, sealing eccentric wear or rupture caused by out of synchronization, and also improving the smoothness of equipment operation and positioning accuracy, such as accurate positioning of the fork of a forklift and alignment of a container by a reach stacker.

[0039] In the embodiment, the electromagnetic valve 6 is powered to automatically complete oil injection and air discharge, the process is integrated into the system initialization process, manual repeated operation of the oil cylinder or the air discharge valve is not needed, the whole machine debugging / maintenance time is shortened, the air discharge effect does not depend on the experience of the operator, the result is consistent and reliable, human errors are excluded, the device delivery and maintenance turnover rate is accelerated, and the downtime cost is reduced.

[0040] In this embodiment, the air accumulated in the connecting pipe between the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 is quickly discharged, which can avoid cavitation caused by the bursting of bubbles under high pressure, reduce the component damage rate, and extend the service life of the system.

[0041] In this embodiment, the hydraulic system only requires the addition of a two-position four-way solenoid valve 6, without the need for additional sensors or complex control programs, resulting in low cost. This tandem cylinder synchronous hydraulic system can be added to existing tandem cylinder systems, reducing the modification cost of existing cylinder systems.

[0042] In this embodiment, the solenoid valve 6 is a two-position four-way solenoid valve. When the solenoid valve 6 is energized, the third port P is connected to the first port A to achieve oil filling, and the second port B is connected to the fourth port T to achieve venting. When the solenoid valve 6 is de-energized, the third port P is disconnected from the first port A, and the second port B and the fourth port T are also disconnected. At this time, the solenoid valve 6 does not participate in operation.

[0043] In some embodiments, to ensure that the second port B and the fourth port T are connected when the solenoid valve 6 is energized, thereby venting, a return oil check valve 7 is provided on the venting circuit to prevent hydraulic oil in the hydraulic oil tank 9 from entering the solenoid valve 6 through the fourth port T. That is, the series-connected synchronous hydraulic system also includes a return oil check valve 7, which is located between the fourth port T of the solenoid valve 6 and the hydraulic oil tank 9, and the return oil check valve 7 connects the fourth port T to the hydraulic oil tank 9.

[0044] like Figure 1 When solenoid valve 6 is energized, the third port P connects to the first port A. Hydraulic oil in hydraulic tank 9 enters solenoid valve 6 through the third port P, and then exits through the first port A, entering the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4. Simultaneously, gas in the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4, as well as gas in the pipe connecting the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4, enters solenoid valve 6 through the second port B, and then exits through the fourth port T, entering hydraulic tank 9 through return check valve 7, thus achieving venting.

[0045] By setting the return oil check valve 7, normal venting is ensured, and precise control of the oil circuit is achieved.

[0046] In some embodiments, the tandem cylinder synchronous hydraulic system further includes a working pump 8, the outlet of which is connected to the third interface P of the solenoid valve 6, and the inlet of which is connected to the hydraulic oil tank 9. The connection between the inlet of the working pump 8 and the hydraulic oil tank 9 enables the output of hydraulic oil from the tank 9, providing power for the delivery of hydraulic oil and ensuring that the hydraulic oil can be delivered to a designated location, thus guaranteeing the normal operation of the tandem cylinder synchronous hydraulic system.

[0047] In some embodiments, the tandem cylinder synchronous hydraulic system further includes a main control valve 1, which includes a first oil port T1, a second oil port T2, a third oil port T3, and a fourth oil port T4.

[0048] The first oil port T1 is connected to the large cavity of the first oil tank. The second oil port T2 is connected to the small cavity of the second oil cylinder 4. The third oil port T3 is connected to the hydraulic oil tank 9. The fourth oil port T4 is connected to the outlet of the working pump 8.

[0049] When the main control valve 1 is in the first working position, the first oil port T1 is connected to the fourth oil port T4, and the second oil port T2 is connected to the third oil port T3. At this time, the hydraulic oil output by the working pump 8 enters the main control valve 1 through the fourth oil port T4, and then exits through the first oil port T1 to the large chamber of the first cylinder 3. The hydraulic oil entering the large chamber of the first cylinder 3 compresses the hydraulic oil in the small chamber of the first cylinder 3. The hydraulic oil in the small chamber of the first cylinder 3 is then output and transported to the large chamber of the second cylinder 4. The hydraulic oil entering the large chamber of the second cylinder 4 pushes the push rod of the second cylinder 4 to extend, and the first cylinder 3 and the second cylinder 4 extend synchronously. At this time, the hydraulic oil in the small chamber of the second cylinder 4 enters the main control valve 1 through the second oil port T2, and then exits through the third oil port T3 to the hydraulic oil tank 9, realizing oil return. Because the third valve port of the main control valve 1 is connected to the hydraulic oil tank 9 and the fourth valve port is connected to the working pump 8, when the main control valve 1 is in the first working position, the second oil cylinder 4 retracts as the first oil cylinder 3 extends, and the two oil cylinders form a rigid linkage.

[0050] When the main control valve 1 is in the second working position, and the second oil port T2 is connected to the fourth oil port T4, the first oil port T1 is connected to the third oil port T3. At this time, the hydraulic oil output by the working pump 8 enters the main control valve 1 through the fourth oil port T4, then exits through the second oil port T2 and goes to the small chamber of the second cylinder 4. The hydraulic oil entering the small chamber of the second cylinder 4 compresses the hydraulic oil in the large chamber of the second cylinder 4. The hydraulic oil in the large chamber of the second cylinder 4 is then output and transported to the small chamber of the first cylinder 3. The hydraulic oil entering the small chamber of the first cylinder 3 pushes the push rod of the first cylinder 3 to retract, and the first cylinder 3 and the second cylinder 4 retract synchronously. At this time, the hydraulic oil in the large chamber of the first cylinder 3 enters the main control valve 1 through the first oil port T1, then exits through the third oil port T3 and goes to the hydraulic oil tank 9, achieving oil return. Because the third valve port of the main control valve 1 is connected to the hydraulic oil tank 9 and the fourth valve port is connected to the working pump 8, when the main control valve 1 is in the second working position, the first oil cylinder 3 retracts accordingly when the second oil cylinder 4 actively extends, thus maintaining the rigid connection of the system.

[0051] In this embodiment, the oil inlet circuit of the active cylinder and the oil return circuit of the driven cylinder are completely decoupled by the main control valve 1, avoiding mutual pressure interference and eliminating the pressure oscillation or delayed response problem that is easy to occur in traditional series cylinder systems.

[0052] In this embodiment, the main control valve 1 keeps the two-stage cylinders in a rigid connection state of "one push and one pull". When the first cylinder 3 extends, its large chamber thrust is directly transmitted to the small chamber return oil circuit of the second cylinder 4, realizing true rigid mechanical synchronization. This ensures that there is no gap or elastic deformation when the load moves, solving the problem of lag in the movement of the series cylinders caused by traditional hose series connection.

[0053] In this embodiment, the main control valve 1 is combined with the structure of the working pump 8 and the hydraulic oil tank 9. In particular, the third valve port of the main control valve 1 is connected to the hydraulic oil tank 9. Bidirectional synchronous control can be achieved by switching only a single valve core. This avoids the problem of needing to use a synchronization valve, balance valve or proportional valve group to ensure synchronization in the traditional solution, simplifies the system, reduces system cost and simplifies system control.

[0054] In some embodiments, the main control valve 1 is a three-position four-way solenoid valve. When the main control valve 1 is in the first operating position, the first port T1 is connected to the fourth port T4, and the second port T2 is connected to the third port T3. When the main control valve 1 is in the second operating position, when the second port T2 is connected to the fourth port T4, the first port T1 is connected to the third port T3. When the main control valve 1 is in the third operating position, the first port T1, the second port T2, the third port T3, and the fourth port T4 of the main control valve 1 are not connected, and at this time, the hydraulic oil output by the working pump 8 cannot enter the main control valve 1.

[0055] Regarding the description of "hydraulic oil entering the large chamber of the first cylinder 3, compressing the hydraulic oil in the small chamber of the first cylinder 3, and then outputting and delivering the hydraulic oil from the small chamber of the first cylinder 3 to the large chamber of the second cylinder 4, the hydraulic oil entering the large chamber of the second cylinder 4 pushes the push rod of the second cylinder 4 to extend, and the first cylinder 3 and the second cylinder 4 extend synchronously," it should be noted that when the solenoid valve 6 is energized, hydraulic oil is delivered to the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 through the solenoid valve 6 to achieve venting. At this time, venting mainly removes the air in the pipe connecting the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4, while very little air accumulates in the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 themselves. Of course, during venting, the gas accumulated in the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 can also be discharged.

[0056] When the first hydraulic cylinder 3 and the second hydraulic cylinder 4, connected in series, are installed with the load being lifted, the extension lengths of the first hydraulic cylinder 3 and the second hydraulic cylinder 4 should be equal to meet the load installation adjustment requirements. When the solenoid valve 6 is venting, hydraulic oil is simultaneously supplied to the small chamber of the first hydraulic cylinder 3 and the large chamber of the second hydraulic cylinder 4. At this time, the pipelines connected to the large chamber of the first hydraulic cylinder 3 and the small chamber of the second hydraulic cylinder 4 are both closed. Furthermore, considering the damping between the cylinder push rod itself and the inner wall of the cylinder, when the hydraulic oil for venting is supplied to the small chamber of the first hydraulic cylinder 3 and the large chamber of the second hydraulic cylinder 4, the hydraulic oil merely fills the original chambers of the small chamber of the first hydraulic cylinder 3 and the large chamber of the second hydraulic cylinder 4, without changing the size of the small chamber of the first hydraulic cylinder 3 and the large chamber of the second hydraulic cylinder 4. That is, at this time, neither the push rod of the first hydraulic cylinder 3 nor the push rod of the second hydraulic cylinder 4 will extend or retract. Therefore, when the main control valve 1 is in the first working position, controlling the first cylinder 3 and the second cylinder 4 to extend synchronously, or when the main control valve 1 is in the second working position, controlling the first cylinder 3 and the second cylinder 4 to retract synchronously, can ensure that the controlled first cylinder 3 and the second cylinder 4 are synchronized.

[0057] In this embodiment, a three-position four-way solenoid valve is set as the main control valve 1, which facilitates the synchronous control of the first cylinder 3 and the second cylinder 4. The control is convenient and fast, the control system is simple, and the cost is low.

[0058] In some embodiments, such as Figure 1 The series-connected hydraulic cylinder synchronous hydraulic system also includes a first balance valve 2.

[0059] The first balancing valve 2 has a first valve port C1, a second valve port C2, a third valve port C3 and a fourth valve port C4.

[0060] The third valve port C3 is connected to the first valve port C1 via a first check valve, and the fourth valve port C4 is connected to the second valve port C2 via a second check valve.

[0061] A first pilot valve is connected between the third valve port C3 and the first valve port C1, and the pilot port of the first pilot valve is connected to the fourth valve port C4.

[0062] A second pilot valve is connected between the fourth valve port C4 and the second valve port C2, and the pilot port of the second pilot valve is connected to the third valve port C3.

[0063] The first valve port C1 is connected to the large chamber of the first oil cylinder 3, the second valve port C2 is connected to the small chamber of the second oil cylinder 4, the third valve port C3 is connected to the first oil port T1 of the main control valve 1, and the fourth valve port C4 is connected to the second oil port T2 of the main control valve 1.

[0064] like Figure 1 As shown, when the main control valve 1 is in the first working position, the first oil port T1 is connected to the fourth oil port T4, and the second oil port T2 is connected to the third oil port T3. At this time, the hydraulic oil output by the working pump 8 enters the main control valve 1 through the fourth oil port T4, and then is output through the first oil port T1 to the third valve port C3 of the first balance valve 2. The hydraulic oil conducts the first check valve between the third valve port C3 and the first valve port C1, and also conducts the second pilot valve between the fourth valve port C4 and the second valve port C2. The hydraulic oil entering the first balance valve 2 enters the large chamber of the first cylinder 3 through the first check valve and the first valve port C1. The hydraulic oil entering the large chamber of the first cylinder 3 compresses the hydraulic oil in the small chamber of the first cylinder 3. The hydraulic oil in the small chamber of the first cylinder 3 is output and transported to the large chamber of the second cylinder 4. The hydraulic oil entering the large chamber of the second cylinder 4 pushes the push rod of the second cylinder 4 to extend, and the first cylinder 3 and the second cylinder 4 extend synchronously. At this time, the small chamber of the second cylinder 4 is compressed, and the hydraulic oil in the small chamber of the second cylinder 4 enters the first balance valve 2 through the second valve port C2, and is output through the second pilot valve in the first balance valve 2, and is output through the fourth valve port C4 of the first balance valve 2. It then enters the main control valve 1 through the second oil port T2, and is output through the third oil port T3 to the hydraulic oil tank 9 to realize oil return.

[0065] When the main control valve 1 is in the second working position, the hydraulic oil output from the second valve port C2 of the main control valve 1 enters the first balance valve 2 through the third valve port C3 of the first balance valve 2. At this time, the hydraulic oil connects the second check valve and the first pilot valve. The second check valve is used to deliver hydraulic oil to the small chamber of the second cylinder 4, and the first pilot valve is used to return oil to the large chamber of the first cylinder 3.

[0066] In this embodiment, a first balance valve 2 is provided. Through a cross-pilot control mechanism, the stall and pressure impact problems of the tandem cylinders under sudden unloading and heavy load conditions are solved, achieving bidirectional load safety locking and overspeed movement suppression. For example, when the main control valve 1 is in the third working position, the first balance valve 2 closes the inlet and outlet of the two cylinders to prevent the large chamber (bearing chamber) of the first cylinder 3 and the small chamber (support chamber) of the second cylinder 4 from retracting due to their own weight, such as when the telescopic boom suddenly loses power and the boom falls.

[0067] In this embodiment, a cross-pilot design (the first pilot valve is controlled by the fourth valve port C4, and the second pilot valve is controlled by the third valve port C3) deeply couples the balancing functions of the two cylinders. When a single cylinder is under a heavy load (such as when the second cylinder 4 retracts at overspeed), the other cylinder (the large chamber of the first cylinder 3) automatically establishes back pressure damping, avoiding the response lag problem of traditional independent balancing valves, improving the shock resistance of the oil tank, and eliminating the "nodding" vibration phenomenon of multi-stage cylinders.

[0068] In this embodiment, both one-way valves and two pilot valves are integrated into the first balancing valve 2 to obtain a single valve block, reducing valve body leakage points, saving installation space, and adapting to the compact layout of engineering machinery.

[0069] In this embodiment, the first balance valve 2 and the main control valve 1 are combined to achieve synergistic effect. When the main control valve 1 switches the oil circuit direction (working position), the first balance valve 2 automatically switches the pilot control source to achieve seamless adaptation of the cylinder's push / pull operation.

[0070] In some embodiments, see Figure 1 The tandem hydraulic cylinder synchronous system also includes a second balance valve 5.

[0071] The second balancing valve 5 has valve port one V1, valve port two V2, valve port three V3 and valve port four V4.

[0072] The valve port 3 (V3) is connected to the valve port 1 (V1) via a one-way valve, and the valve port 4 (V4) is directly connected to the valve port 2 (V2).

[0073] A pilot valve is connected between valve port 3 (V3) and valve port 1 (V1). The pilot port of the pilot valve is connected to valve port 4 (V4). A check valve is provided between the pilot port of the pilot valve and valve port 4 (V4). The check valve is connected to the oil passage from valve port 4 (V4) to the pilot port of the pilot valve.

[0074] The hydraulic oil output from the small chamber of the first cylinder 3 enters the second balance valve 5 through the valve port 3V3, which opens the check valve 1. The check valve 1 is used to deliver hydraulic oil to the large chamber of the second cylinder 4. The small chamber of the second cylinder 4 is compressed. The hydraulic oil in the small chamber of the second cylinder 4 enters the second balance valve 5 through the valve port 2V2, and then is output through the valve port 4V4 to the second valve port C2 of the first balance valve 2. Then it is output through the second pilot valve and the fourth valve port C4, and returns through the second oil port T2 and the third oil port T3 of the main control valve 1.

[0075] Hydraulic oil output from the second port C2 of the first balance valve 2 enters the second balance valve 5 through port V4, opening the oil passage from port V4 to port V2. Simultaneously, check valve 2 and pilot valve 1 are activated sequentially. The open oil passage from port V4 to port V2 is used to supply hydraulic oil to the small chamber of the second cylinder 4. Pilot valve 1 is activated to output hydraulic oil from the large chamber of the second cylinder 4. The hydraulic oil in the large chamber of the second cylinder 4 enters the small chamber of the first cylinder 3 through port V1, pilot valve 1, and port V3.

[0076] By setting the first balance valve 2 and the second balance valve 5, and combining them with the main control valve 1, the first cylinder 3 and the second cylinder 4 are synchronously controlled. This control system is simple, low-cost, easy to control, and convenient to operate.

[0077] The function of the second balance valve 5 is basically the same as that of the first balance valve 2. In addition, the second balance valve 5 and the first balance valve 2 are used together to further achieve synergistic effect. When the main control valve 1 switches the oil circuit direction (working position), the first balance valve 2 automatically switches the pilot control source, and the second balance valve 5 also changes the pilot control source synchronously to achieve seamless adaptation of the cylinder's push / pull operation.

[0078] In some embodiments, the first cylinder 3 includes a first cylinder 3 push rod, and the second cylinder 4 includes a second cylinder 4 push rod. The effective working areas of the first cylinder 3 push rod and the second cylinder 4 push rod are adapted to ensure that the two cylinders move synchronously.

[0079] A method for synchronizing tandem hydraulic cylinders, using the aforementioned tandem hydraulic cylinder synchronization hydraulic system for control; The process includes, after the assembly of the tandem hydraulic system, venting the gas from the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4, including the following steps: When solenoid valve 6 is energized, working pump 8 is started. Working pump 8 outputs hydraulic oil, which enters solenoid valve 6 through the third valve port C3, and then exits through the first valve port C1 of solenoid valve 6, entering the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 respectively, filling the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 respectively. At the same time, the gas in the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 enters solenoid valve 6 through the second valve port C2, and finally exits through the fourth valve port C4 of solenoid valve 6 to the hydraulic oil tank 9.

[0080] Through this control method and procedures, after the solenoid valve 6 is energized, hydraulic oil is precisely injected into the small chamber of the first cylinder 3 and the large chamber of the second cylinder 4 (the key nodes where air is most easily accumulated in series cylinders). Simultaneously, the gas in both chambers is directed to the oil tank. This automatically and quickly expels gas from the series cylinders and the pipes connecting the two cylinders, precisely targeting the air release and completely eliminating synchronization risks. Furthermore, the venting effect is independent of operator experience, providing consistent and reliable results, eliminating human error. There is no need for repeated manual operation of the cylinders or venting valves, shortening the overall machine commissioning / maintenance time. Additionally, it accelerates equipment delivery and maintenance turnaround times, reducing downtime costs.

[0081] During this control scheme, the working pump 8 starts at low pressure (only needing to overcome exhaust resistance), reducing energy consumption. During the exhaust process, the oil circulates back to the oil tank, without triggering the main control valve 1, thus avoiding the risk of misoperation.

[0082] In this control scheme and process, forced automatic venting can be performed after each maintenance to eliminate gradual asynchrony caused by air accumulation, reduce cavitation damage, and extend the life of hydraulic components.

[0083] In this control scheme and process, the venting step, through precise oil circuit design and automated execution, solves the long-standing pain point in the field of tandem hydraulic cylinders that "venting depends on experience and the effect cannot be verified," providing a reliable foundation for high-precision synchronous hydraulic systems.

[0084] The tandem hydraulic cylinder synchronization method further includes controlling the synchronous extension and retraction of the first hydraulic cylinder 3 and the second hydraulic cylinder 4 during their operation, including the following steps: When solenoid valve 6 is de-energized, main control valve 1 is in the first working position, and working pump 8 outputs hydraulic oil to main control valve 1. Main control valve 1 delivers hydraulic oil through first oil port T1 and first balance valve 2 to the large chamber of the first oil tank. The hydraulic oil enters the large chamber of the first cylinder 3 and compresses the space of the small chamber of the first cylinder 3. The hydraulic oil in the small chamber of the first cylinder 3 is output and enters the large chamber of the second cylinder 4 through the second balance valve 5. The first cylinder 3 and the second cylinder 4 extend synchronously. When solenoid valve 6 is de-energized, main control valve 1 is in the second working position, and working pump 8 outputs hydraulic oil to main control valve 1. Main control valve 1 delivers hydraulic oil through second oil port T2 and second balance valve 5 to the small chamber of the second oil tank. The hydraulic oil enters the small chamber of the second cylinder 4 and compresses the space of the large chamber of the second cylinder 4. The hydraulic oil in the large chamber of the second cylinder 4 is output and enters the small chamber of the second cylinder 4 through the second balance valve 5. The first cylinder 3 and the second cylinder 4 retract synchronously.

[0085] In this control scheme and process, the synchronous control of the two hydraulic cylinders can be achieved through this control method and steps, resulting in good cylinder synchronization and improved resistance to eccentric loads.

[0086] This control scheme and process achieves zero-energy power transmission, utilizing the change in cylinder cavity volume as the synchronous driving power of the cylinder, with no throttling loss and no pressure drop from the flow divider valve, significantly improving the flow utilization rate of the working pump 8.

[0087] In this control scheme and process, two hydraulic cylinders are connected in series, and the change in the volume of the cylinder cavity is used as the synchronous driving force for the hydraulic cylinders. The hydraulic fluid directly and rigidly transmits pressure between the connected cavities, which greatly shortens the response delay and overcomes the existing problem of asynchronous start-up of hydraulic cylinders.

[0088] A telescopic boom forklift truck includes the aforementioned tandem cylinder synchronous hydraulic system, which ensures the synchronous extension and retraction of the tandem cylinders, thus ensuring the normal and efficient operation of the entire machine.

[0089] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A tandem hydraulic cylinder synchronous system, characterized in that, It includes a first hydraulic cylinder, a second hydraulic cylinder, a solenoid valve, and a hydraulic oil tank. The solenoid valve has a first interface, a second interface, a third interface, and a fourth interface. The first interface is connected to the small cavity of the first cylinder and the large cavity of the second cylinder; the second interface is connected to the small cavity of the first cylinder and the large cavity of the second cylinder; the third interface is connected to the hydraulic oil tank; and the fourth interface is connected to the hydraulic oil tank. When the solenoid valve is energized, the third interface is connected to the first interface, and the hydraulic oil in the hydraulic oil tank enters the small chamber of the first cylinder and the large chamber of the second cylinder in sequence through the third interface and the first interface respectively; when the solenoid valve is energized, the second interface and the fourth interface are connected, and the gas in the small chamber of the first cylinder and the large chamber of the second cylinder enters the hydraulic oil tank in sequence through the second interface and the fourth interface.

2. The tandem hydraulic cylinder synchronous hydraulic system according to claim 1, characterized in that, It also includes a return oil check valve, which is disposed between the fourth port of the solenoid valve and the hydraulic oil tank, and the return oil check valve connects the fourth port to the hydraulic oil tank oil circuit.

3. The tandem hydraulic cylinder synchronous hydraulic system according to claim 1, characterized in that, It also includes a working pump, the outlet of which is connected to the third interface of the solenoid valve, and the inlet of which is connected to the hydraulic oil tank.

4. The tandem hydraulic cylinder synchronous hydraulic system according to claim 3, characterized in that, It also includes a main control valve, which includes a first oil port, a second oil port, a third oil port and a fourth oil port; The first oil port is connected to the large cavity of the first oil tank; the second oil port is connected to the small cavity of the second oil cylinder; the third oil port is connected to the hydraulic oil tank; and the fourth oil port is connected to the outlet of the working pump. When the main control valve is in the first working position, the first oil port is connected to the fourth oil port, and the second oil port is connected to the third oil port; When the main control valve is in the second working position, and the second oil port is connected to the fourth oil port, the first oil port is connected to the third oil port.

5. The tandem hydraulic cylinder synchronous hydraulic system according to claim 4, characterized in that, It also includes a first balancing valve; The first balancing valve has a first valve port, a second valve port, a third valve port, and a fourth valve port; The third valve port is connected to the first valve port through a first check valve, and the fourth valve port is connected to the second valve port through a second check valve; A first pilot valve is connected between the third valve port and the first valve port, and the pilot port of the first pilot valve is connected to the fourth valve port. A second pilot valve is connected between the fourth valve port and the second valve port, and the pilot port of the second pilot valve is connected to the third valve port. The first valve port is connected to the large chamber of the first oil cylinder, the second valve port is connected to the small chamber of the second oil cylinder, the third valve port is connected to the first oil port of the main control valve, and the fourth valve port is connected to the second oil port of the main control valve.

6. The tandem hydraulic cylinder synchronous hydraulic system according to claim 5, characterized in that, It also includes a second balancing valve; The second balancing valve has valve port one, valve port two, valve port three and valve port four; The valve port three is connected to the valve port one through a one-way valve one, and the valve port four is directly connected to the valve port two; A pilot valve is connected between valve port three and valve port one. The pilot port of the pilot valve is connected to valve port four. A check valve is provided between the pilot port of the pilot valve and valve port four. The check valve is connected to the oil passage from valve port four to the pilot port of the pilot valve.

7. The tandem hydraulic cylinder synchronous hydraulic system according to any one of claims 1 to 6, characterized in that, The first hydraulic cylinder includes a first hydraulic cylinder push rod, and the second hydraulic cylinder includes a second hydraulic cylinder push rod, wherein the effective working areas of the first hydraulic cylinder push rod and the second hydraulic cylinder push rod are adapted to each other.

8. A method for synchronizing tandem hydraulic cylinders, characterized in that, The system is controlled by a tandem hydraulic cylinder synchronous hydraulic system as described in any one of claims 1 to 7; After the tandem hydraulic system is assembled, the gas in the small chamber of the first cylinder and the large chamber of the second cylinder is discharged. This includes the following steps: When the solenoid valve is energized, the working pump is started, and the working pump outputs hydraulic oil. The hydraulic oil enters the solenoid valve through the third valve port, and then exits through the first valve port of the solenoid valve, entering the small chamber of the first cylinder and the large chamber of the second cylinder respectively, filling the small chamber of the first cylinder and the large chamber of the second cylinder respectively. At the same time, the gas in the small chamber of the first cylinder and the gas in the large chamber of the second cylinder enter the solenoid valve through the second valve port, and finally exits through the fourth valve port of the solenoid valve to the hydraulic oil tank.

9. The method for synchronizing tandem hydraulic cylinders according to claim 8, characterized in that, It also includes controlling the synchronous extension and retraction of the first and second hydraulic cylinders during their operation, including the following steps: When the solenoid valve is de-energized, the main control valve is in the first working position. The working pump outputs hydraulic oil to the main control valve. The main control valve delivers the hydraulic oil to the large chamber of the first cylinder through the first oil port and the first balance valve. The hydraulic oil entering the large chamber of the first cylinder compresses the space of the small chamber of the first cylinder. The hydraulic oil in the small chamber of the first cylinder is output and enters the large chamber of the second cylinder through the second balance valve. The first cylinder and the second cylinder extend synchronously. When the solenoid valve is de-energized, the main control valve is in the second working position. The working pump outputs hydraulic oil to the main control valve. The main control valve delivers the hydraulic oil to the small chamber of the second cylinder through the second oil port and the second balance valve. The hydraulic oil entering the small chamber of the second cylinder compresses the space of the large chamber of the second cylinder. The hydraulic oil in the large chamber of the second cylinder is output and enters the small chamber of the second cylinder through the second balance valve. The first cylinder and the second cylinder retract synchronously.

10. A telescopic boom forklift, characterized in that, It includes the tandem hydraulic cylinder synchronous hydraulic system as described in any one of claims 1 to 7.

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