Hydraulic system with adjustable speed and force, control method thereof, and engineering machinery

Abstract

The application provides a hydraulic system with adjustable speed and force, comprising an oil tank, a hydraulic pump, a motor, a hydraulic directional valve, a first directional valve, a second directional valve, a first throttle valve, a second throttle valve, a first hydraulic cylinder and a second hydraulic cylinder; the piston rods of the first hydraulic cylinder and the second hydraulic cylinder are arranged in parallel and move synchronously, and the inner diameter of the first hydraulic cylinder is smaller than that of the second hydraulic cylinder. The hydraulic pump is connected to the first hydraulic cylinder and the second hydraulic cylinder through a main oil path; the oil inlet of the hydraulic directional valve is communicated with the main oil path, and the two working oil ports are communicated with the first oil cavity and the second oil cavity of the first hydraulic cylinder respectively; the oil inlets of the first directional valve and the second directional valve are communicated with the main oil path, and the oil outlets are communicated to the two hydraulic control ends of the hydraulic directional valve respectively; the oil inlets of the first throttle valve and the second throttle valve are communicated with the main oil path, the oil outlet of the first throttle valve is communicated to the second oil cavity of the second hydraulic cylinder, and the oil outlet of the second throttle valve is communicated to the first oil cavity of the second hydraulic cylinder.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic technology, and in particular to a hydraulic system with adjustable speed and force, a control method thereof, and engineering machinery. Background Art

[0002] As a transmission technology, hydraulic systems are widely used in various fields because they can generate significant force, offer stepless speed regulation over a wide range, and offer excellent operational performance. Pressure and flow are two key factors in hydraulic system regulation, correspondingly determining the system's output force and speed. Typically, these are controlled primarily through pressure and flow valves or variable displacement pumps. However, in some specialized applications, such as those limited by installation space or when the power source hydraulic components are already defined, some commonly used speed and pressure regulation systems may suffer from drawbacks such as bulk, low efficiency, and inflexibility.

[0003] Figure 1 The schematic diagram of the hydraulic system of a conventional molding machine includes: a filter 1, a metering pump 2, solenoid directional valves 3, 6, 7, and 8, a relief valve 4, a pressure reducing valve 5, dual hydraulically controlled check valves 9, 10, and 11, one-way throttle valves 12, 13, and 14, pressure relays 15 and 20, accumulators 16 and 19, a master cylinder 17, a slave cylinder 18, and a molding cylinder 21. In the illustrated state, the electromagnets of all solenoid valves are de-energized, and the hydraulic oil from metering pump 2 is unloaded through two-position, four-way solenoid directional valve 3. When the hydraulic system is in operation, the electromagnet 7YA of the two-position, four-way solenoid directional valve 3 is first energized, at which point the entire hydraulic system operates at the set working pressure. Pressing the operating button simultaneously energizes the electromagnets 1YA and 3YA of the three-position, four-way solenoid directional valves 6 and 7. At this point, the three-position, four-way solenoid directional valves 6 and 7 are switched to the left position. Hydraulic oil flows through the pressure reducing valve 5 and enters the active cylinder 17 and the slave cylinder 18, causing them to move synchronously and rapidly to the designated position. The speed is regulated by the one-way throttle valves 12 and 13. When the active cylinder 17 and the slave cylinder 18 reach their set positions, the electromagnet 5YA of the three-position, four-way solenoid directional valve 8 is energized, causing hydraulic oil to enter the rodless chamber of the forming cylinder 21. The hydraulic oil in the rod chamber returns to the oil tank, and the forming cylinder 21, along with the active cylinder 17 and the slave cylinder 18, slowly moves to overcome the heavy load.

[0004] When the hydraulic system is required to move at high speed under light load, this is achieved by controlling the master-slave cylinder system. When the hydraulic system is required to output force to overcome heavy load, this is achieved by simultaneously controlling the forming cylinder system and the master-slave cylinder system.

[0005] The above prior art also has the following shortcomings:

[0006] 1. Its master-slave cylinder system uses the same hydraulic components, which has a complex structure, occupies a large space, has low space utilization, and is costly.

[0007] 2. The master and slave cylinders use the same system control to achieve synchronization, but when the load difference between the two cylinders is large and uncertain, the synchronization ability is weak and the flexibility is poor.

[0008] 3. The inlet end throttling speed regulation is adopted, which has poor stability and cannot meet the working conditions of negative load.

[0009] 4. The use of electromagnetic reversing valve affects the switching stability of the actuator and is not suitable for system conditions requiring large flow. Summary of the Invention

[0010] The purpose of the present invention is to provide a hydraulic system with adjustable speed and force, a control method thereof, and engineering machinery, which realizes the step-by-step adjustment of speed and force through parallel double-rod hydraulic cylinders, achieves the effect of low speed for heavy loads and high speed for light loads, and at least partially solves the above-mentioned technical problems.

[0011] The present invention provides a hydraulic system with adjustable speed and force, comprising an oil tank, a hydraulic pump connected to the oil tank, and an electric motor driving the hydraulic pump, and further comprising a hydraulic reversing valve, a first reversing valve, a second reversing valve, a first throttle valve, a second throttle valve, a first hydraulic cylinder, and a second hydraulic cylinder; the piston rods of the first hydraulic cylinder and the second hydraulic cylinder are arranged in parallel and move synchronously in the same direction, and the inner diameter of the first hydraulic cylinder is smaller than the inner diameter of the second hydraulic cylinder; the hydraulic pump is connected to the first hydraulic cylinder and the second hydraulic cylinder through a main oil circuit; wherein the oil inlet of the hydraulic reversing valve is connected to the main oil circuit The two working oil ports of the hydraulic reversing valve are respectively connected with the first oil chamber and the second oil chamber of the first hydraulic cylinder, the oil inlets of the first reversing valve and the second reversing valve are connected with the main oil circuit, and the oil outlets of the first reversing valve and the second reversing valve are respectively connected to the two hydraulic control ends of the hydraulic reversing valve; the oil inlets of the first throttle valve and the second throttle valve are connected with the main oil circuit, the oil outlet of the first throttle valve is connected to the second oil chamber of the second hydraulic cylinder through the first branch oil circuit, and the oil outlet of the second throttle valve is connected to the first oil chamber of the second hydraulic cylinder through the second branch oil circuit.

[0012] Furthermore, the first reversing valve includes a first directional valve assembly, a second directional valve assembly and a first solenoid reversing valve, the working oil port B of the second directional valve assembly and the oil inlet P of the first solenoid reversing valve are connected to the main oil circuit, the working oil port A and the working oil port B of the first solenoid reversing valve are respectively connected to the control oil port X of the first directional valve assembly and the control oil port X of the second directional valve assembly, the working oil port A of the first directional valve assembly and the working oil port A of the second directional valve assembly are connected to one of the hydraulic control ends of the hydraulic reversing valve, the return oil port T of the first solenoid reversing valve and the working oil port B of the first directional valve assembly are connected to the return oil port Oil tank; the second reversing valve includes a third directional valve assembly, a fourth directional valve assembly and a second solenoid reversing valve, the working oil port B of the third directional valve assembly and the oil inlet P of the second solenoid reversing valve are connected to the main oil circuit, the working oil port A and the working oil port B of the second solenoid reversing valve are respectively connected to the control oil port X of the third directional valve assembly and the control oil port X of the fourth directional valve assembly, the working oil port A of the third directional valve assembly and the working oil port A of the fourth directional valve assembly are connected to the other hydraulic control end of the hydraulic reversing valve, and the return oil port T of the second solenoid reversing valve and the working oil port B of the fourth directional valve assembly are connected to the return oil tank.

[0013] Furthermore, the first throttle valve includes a first throttle valve assembly, a fifth directional valve assembly and a third solenoid reversing valve, the working oil port B of the fifth directional valve assembly and the oil inlet P of the third solenoid reversing valve are connected to the main oil circuit, the working oil port A and the working oil port B of the third solenoid reversing valve are respectively connected to the control oil port X of the first throttle valve assembly and the control oil port X of the fifth directional valve assembly, the working oil port A of the first throttle valve assembly and the working oil port A of the fifth directional valve assembly are connected to the second oil chamber of the second hydraulic cylinder through the first branch oil circuit, the return oil port T of the third solenoid reversing valve and the working oil port B of the first throttle valve assembly are connected to the return oil chamber of the second hydraulic cylinder, Oil tank; the second throttle valve includes a sixth directional valve assembly, a second throttle valve assembly and a fourth solenoid reversing valve, the working oil port B of the sixth directional valve assembly and the oil inlet P of the fourth solenoid reversing valve are connected to the main oil circuit, the working oil port A and the working oil port B of the fourth solenoid reversing valve are respectively connected to the control oil port X of the sixth directional valve assembly and the control oil port X of the second throttle valve assembly, the working oil port A of the sixth directional valve assembly and the working oil port A of the second throttle valve assembly are connected to the first oil chamber of the second hydraulic cylinder through the second branch oil circuit, and the return oil port T of the fourth solenoid reversing valve and the working oil port B of the second throttle valve assembly are connected to the return oil tank.

[0014] Furthermore, it also includes a third reversing valve and a hydraulic lock; the hydraulic lock has a first oil inlet, a second oil inlet, a first oil outlet and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil branch line, the second oil inlet and the second oil outlet are located on the second oil branch line, the first oil inlet of the hydraulic lock is connected to the oil outlet of the first throttle valve, the first oil outlet of the hydraulic lock is connected to the second oil chamber of the second hydraulic cylinder, the second oil inlet of the hydraulic lock is connected to the oil outlet of the second throttle valve, and the second oil outlet of the hydraulic lock is connected to the first oil chamber of the second hydraulic cylinder.

[0015] Furthermore, the third reversing valve includes a seventh directional valve assembly, an eighth directional valve assembly and a fifth solenoid reversing valve, the working oil port A of the eighth directional valve assembly and the oil inlet P of the fifth solenoid reversing valve are connected to the main oil circuit, the working oil port A and the working oil port B of the fifth solenoid reversing valve are respectively connected to the control oil port X of the seventh directional valve assembly and the control oil port X of the eighth directional valve assembly, the working oil port A of the seventh directional valve assembly and the working oil port B of the eighth directional valve assembly are connected to the hydraulic lock, and the return oil port T of the fifth solenoid reversing valve and the working oil port B of the seventh directional valve assembly are connected to the return oil tank; the hydraulic lock assembly It includes a first pressure valve assembly, a second pressure valve assembly, a first shuttle valve and a second shuttle valve. The first oil inlet of the hydraulic lock is the working oil port A of the first pressure valve assembly, the first oil outlet of the hydraulic lock is the working oil port B of the first pressure valve assembly, the second oil inlet of the hydraulic lock is the working oil port A of the second pressure valve assembly, and the second oil outlet of the hydraulic lock is the working oil port B of the second pressure valve assembly. The first shuttle valve is connected to the control oil port of the first pressure valve assembly, and the second shuttle valve is connected to the control oil port of the second pressure valve assembly. The control ends of the first shuttle valve and the second shuttle valve are both connected to the third reversing valve.

[0016] Furthermore, the first oil distribution line is provided with a first overflow valve and a first pressure gauge, and the second oil distribution line is provided with a second overflow valve and a second pressure gauge.

[0017] Furthermore, the main oil circuit is also provided with an unloading valve, which includes a pressure valve assembly, a sixth solenoid reversing valve and a third overflow valve; the main oil circuit is also provided with a third pressure gauge, a plug-in one-way valve, a pressure sensor and a fine filter; the hydraulic pump is a fixed-displacement pump.

[0018] Furthermore, the first hydraulic cylinder and the second hydraulic cylinder share the same cylinder head and cylinder bottom.

[0019] The present invention also provides a control method for a hydraulic system with adjustable speed and force, which is characterized in that, for controlling the above-mentioned hydraulic system with adjustable speed and force, the control method includes: when the piston rod of the hydraulic cylinder needs to be extended, when the hydraulic system with adjustable speed and force is lightly loaded, controlling the second oil chamber of the first hydraulic cylinder to flow oil or controlling the second oil chamber of the second hydraulic cylinder to flow oil; when the hydraulic system with adjustable speed and force is heavily loaded, controlling the second oil chamber of the first hydraulic cylinder to flow oil or controlling the second oil chamber of the second hydraulic cylinder to flow oil, or controlling the second oil chamber of the first hydraulic cylinder and the second oil chamber of the second hydraulic cylinder to flow oil simultaneously; when the piston rod of the hydraulic cylinder needs to be retracted, when the hydraulic system with adjustable speed and force is lightly loaded, controlling the first oil chamber of the first hydraulic cylinder to flow oil or controlling the first oil chamber of the second hydraulic cylinder to flow oil; when the hydraulic system with adjustable speed and force is heavily loaded, controlling the first oil chamber of the first hydraulic cylinder to flow oil or controlling the first oil chamber of the second hydraulic cylinder to flow oil, or controlling the first oil chamber of the first hydraulic cylinder and the first oil chamber of the second hydraulic cylinder to flow oil simultaneously.

[0020] The present invention also provides an engineering machine, characterized in that it comprises the above-mentioned hydraulic system with adjustable speed and force.

[0021] The hydraulic system with adjustable speed and force, its control method, and engineering machinery provided by the present invention have the following beneficial effects:

[0022] 1. The hydraulic system with adjustable speed and force adopts a large-diameter hydraulic cylinder (second hydraulic cylinder) and a small-diameter hydraulic cylinder (first hydraulic cylinder) in parallel to form an integrated double-rod hydraulic cylinder. When using a fixed-displacement pump, the speed and force of the system can be adjusted in stages through the on-off combination of its oil holes, achieving the effect of low speed for heavy load and high speed for light load, with good synchronization effect and can be applied to harsh environments.

[0023] 2. The design of a simpler hydraulic system controls the hydraulic double cylinders, which is low in cost, convenient and flexible to control, and easy to implement.

[0024] 3. The cartridge valve system facilitates system commissioning and updates, boasts a compact structure and high space utilization. Low control current facilitates system program control. Low leakage meets high pressure-maintaining requirements, and features strong anti-contamination capabilities and reliable performance.

[0025] 4. The parallel dual hydraulic cylinders (the first hydraulic cylinder and the second hydraulic cylinder) are controlled by separate circuits, which makes the control convenient and flexible. Furthermore, the system is equipped with an unloading circuit, which helps to reduce reactive power loss and oil source heating during the waiting period. In addition, the outlet throttling speed regulation and hydraulic reversing valve are used to improve the stability of the system and adapt to negative load conditions.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above-mentioned speed and force adjustable hydraulic system and its control method and other purposes, features and advantages of engineering machinery of the present invention more obvious and easy to understand, the following specifically cites preferred embodiments and explains them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the hydraulic system of an existing molding machine.

[0028] Figure 2 A schematic structural diagram of a hydraulic system with adjustable speed and force according to a preferred embodiment of the present invention.

[0029] Figure 3 Schematic diagram of the implementation principle of a hydraulic system with adjustable speed and force according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0030] To further illustrate the technical means and effects of the present invention to achieve the predetermined purpose of the invention, the specific implementation, structure, features and effects of the hydraulic system with adjustable speed and force and its control method and engineering machinery proposed by the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments:

[0031] The aforementioned and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiment with reference to the accompanying drawings. Through the description of the specific embodiments, a deeper and more detailed understanding of the technical means and effects adopted by the present invention to achieve the intended objectives can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the present invention.

[0032] Figure 2 A schematic diagram of the structure of a hydraulic system with adjustable speed and force according to a preferred embodiment of the present invention is shown in FIG. Figure 2 As shown, the hydraulic system with adjustable speed and force includes an oil tank 101, a hydraulic pump 102 connected to the oil tank 101, and an electric motor 103 that drives the hydraulic pump 102. The hydraulic system also includes a hydraulic reversing valve 123, a first reversing valve 203, a second reversing valve 204, a first throttle valve 205, a second throttle valve 206, a first hydraulic cylinder 128, and a second hydraulic cylinder 129. The piston rods of the first hydraulic cylinder 128 and the second hydraulic cylinder 129 are arranged in parallel and move synchronously in the same direction. The inner diameter of the first hydraulic cylinder 128 is smaller than the inner diameter of the second hydraulic cylinder 129.

[0033] The hydraulic pump 102 is connected to the first hydraulic cylinder 128 and the second hydraulic cylinder 129 through a main oil line 300 .

[0034] Specifically, the oil inlet P of the hydraulic reversing valve 123 is connected to the main oil circuit 300, the two working oil ports A and B of the hydraulic reversing valve 123 are respectively connected to the first oil chamber and the second oil chamber of the first hydraulic cylinder 128, the oil inlets of the first reversing valve 203 and the second reversing valve 204 are connected to the main oil circuit 300, and the oil outlets of the first reversing valve 203 and the second reversing valve 204 are respectively connected to the two hydraulic control ends of the hydraulic reversing valve 123.

[0035] The oil inlets of the first throttle valve 205 and the second throttle valve 206 are connected to the main oil circuit 300, the oil outlet of the first throttle valve 205 is connected to the second oil chamber of the second hydraulic cylinder 129 through the first branch oil circuit 310, and the oil outlet of the second throttle valve 206 is connected to the first oil chamber of the second hydraulic cylinder 129 through the second branch oil circuit 320. The oil flow rates of the first throttle valve 205 and the second throttle valve 206 are adjustable.

[0036] The speed and force adjustable hydraulic system of the present invention is achieved by arranging a large-diameter hydraulic cylinder (the second hydraulic cylinder 129) and a small-diameter hydraulic cylinder (the first hydraulic cylinder 128) in parallel to form an integrated double-rod hydraulic cylinder, and adopts separate circuits to control the large-diameter hydraulic cylinder and the small-diameter hydraulic cylinder respectively. The control is convenient and flexible, and the effect of heavy load and low speed and light load and high speed can be achieved by controlling the on-off combination of the two circuits, and the synchronization effect is good.

[0037] In this embodiment, both the first reversing valve 203 and the second reversing valve 204 are plug-in two-position three-way valves. The first reversing valve 203 is used to control the on / off of the control oil circuit of one hydraulic end of the hydraulic reversing valve 123, while the second reversing valve 204 is used to control the on / off of the control oil circuit of the other hydraulic end of the hydraulic reversing valve 123.

[0038] Specifically, the first reversing valve 203 comprises a first directional valve assembly 111, a second directional valve assembly 112, and a first solenoid reversing valve 211. The first solenoid reversing valve 211 serves as a pilot valve. The working oil port B of the second directional valve assembly 112 and the oil inlet P of the first solenoid reversing valve 211 communicate with the main oil circuit 300. The working oil ports A and B of the first solenoid reversing valve 211 communicate with the control oil port X of the first directional valve assembly 111 and the control oil port X of the second directional valve assembly 112, respectively. The working oil ports A of the first directional valve assembly 111 and A of the second directional valve assembly 112 communicate with one of the hydraulic control ports of the hydraulic reversing valve 123. The oil return port T of the first solenoid reversing valve 211 and the working oil port B of the first directional valve assembly 111 communicate with the oil return tank. When the control electromagnet 2Y of the first solenoid reversing valve 211 is energized, the first reversing valve 203 is conductive.

[0039] Second reversing valve 204 includes a third directional valve assembly 113, a fourth directional valve assembly 114, and a second solenoid reversing valve 212. The working oil port B of the third directional valve assembly 113 and the oil inlet port P of the second solenoid reversing valve 212 are connected to the main oil circuit 300. The working oil ports A and B of the second solenoid reversing valve 212 are connected to the control oil port X of the third directional valve assembly 113 and the control oil port X of the fourth directional valve assembly 114, respectively. The working oil ports A of the third directional valve assembly 113 and A of the fourth directional valve assembly 114 are connected to the other hydraulically controlled end of the hydraulic reversing valve 123. The oil return port T of the second solenoid reversing valve 212 and the working oil port B of the fourth directional valve assembly 114 are connected to the oil tank. When the control electromagnet 3Y of the second solenoid reversing valve 212 is energized, the second reversing valve 204 is turned on.

[0040] In this embodiment, both the first throttle valve 205 and the second throttle valve 206 are plug-in two-position three-way valves. The first throttle valve 205 is used to control the on / off state and the oil flow rate of the first branch oil path 310, while the second throttle valve 206 is used to control the on / off state and the oil flow rate of the second branch oil path 320.

[0041] Specifically, the first throttle valve 205 includes the first throttle valve assembly 115, the fifth directional valve assembly 116, and the third solenoid reversing valve 213. The working oil port B of the fifth directional valve assembly 116 and the oil inlet P of the third solenoid reversing valve 213 are connected to the main oil circuit 300. The working oil ports A and B of the third solenoid reversing valve 213 are connected to the control oil port X of the first throttle valve assembly 115 and the control oil port X of the fifth directional valve assembly 116, respectively. The working oil ports A of the first throttle valve assembly 115 and A of the fifth directional valve assembly 116 are connected to the second oil chamber of the second hydraulic cylinder 129 via the first branch oil circuit 310. The oil return port T of the third solenoid reversing valve 213 and the working oil port B of the first throttle valve assembly 115 are connected to the oil tank. When the control electromagnet 4Y of the third solenoid reversing valve 213 is energized, the first throttle valve 205 is turned on. The oil flow rate of the first throttle valve 205 can be controlled by controlling the control handle of the first throttle valve assembly 115.

[0042] Second throttle valve 206 includes a sixth directional valve assembly 117, a second throttle valve assembly 118, and a fourth solenoid reversing valve 214. The working oil port B of the sixth directional valve assembly 117 and the oil inlet port P of the fourth solenoid reversing valve 214 are connected to the main oil circuit 300. The working oil ports A and B of the fourth solenoid reversing valve 214 are connected to the control oil port X of the sixth directional valve assembly 117 and the control oil port X of the second throttle valve assembly 118, respectively. The working oil ports A of the sixth directional valve assembly 117 and A of the second throttle valve assembly 118 are connected to the first oil chamber of the second hydraulic cylinder 129 via a second branch oil circuit 320. The oil return port T of the fourth solenoid reversing valve 214 and the working oil port B of the second throttle valve assembly 118 are connected to the oil tank. When the control electromagnet 5Y of the fourth solenoid reversing valve 214 is energized, the second throttle valve 206 is energized. The oil flow rate of the second throttle valve 206 can be controlled by controlling the control handle of the second throttle valve assembly 118.

[0043] The speed- and force-adjustable hydraulic system also includes a third reversing valve 207 and a hydraulic lock 208. The third reversing valve 207, located in the control oil circuit, controls the unlocking and locking of the hydraulic lock 208, thereby controlling whether the hydraulic lock 208 is reversely conducting. If, during heavy-load, low-speed operation of the two hydraulic cylinders, external forces cause the second hydraulic cylinder 129 to overspeed or reverse its motion, the hydraulic lock 208 automatically locks its circuit, entering a pressure-maintaining state.

[0044] Specifically, the hydraulic lock 208 has a first oil inlet, a second oil inlet, a first oil outlet and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil branch path 310, and the second oil inlet and the second oil outlet are located on the second oil branch path 320, the first oil inlet of the hydraulic lock 208 is connected to the oil outlet of the first throttle valve 205, the first oil outlet of the hydraulic lock 208 is connected to the second oil chamber of the second hydraulic cylinder 129, the second oil inlet of the hydraulic lock 208 is connected to the oil outlet of the second throttle valve 206, and the second oil outlet of the hydraulic lock 208 is connected to the first oil chamber of the second hydraulic cylinder 129.

[0045] The third reversing valve 207 is a plug-in, two-position, three-way valve. Specifically, the third reversing valve 207 includes the seventh directional valve assembly 119, the eighth directional valve assembly 120, and the fifth solenoid reversing valve 215. The working oil port A of the eighth directional valve assembly 120 and the oil inlet P of the fifth solenoid reversing valve 215 are connected to the main oil circuit 300. The working oil port A and the working oil port B of the fifth solenoid reversing valve 215 are connected to the control oil port X of the seventh directional valve assembly 119 and the control oil port X of the eighth directional valve assembly 120, respectively. The working oil port A of the seventh directional valve assembly 119 and the working oil port B of the eighth directional valve assembly 120 are connected to the hydraulic lock 208. The oil return port T of the fifth solenoid reversing valve 215 and the working oil port B of the seventh directional valve assembly 119 are connected to the oil return tank.

[0046] The hydraulic lock 208 is a plug-in, bidirectional hydraulic lock. It includes a first pressure valve assembly 121, a second pressure valve assembly 122, a first shuttle valve 216, and a second shuttle valve 217. The first oil inlet of the hydraulic lock 208 is the working oil port A of the first pressure valve assembly 121, and the first oil outlet is the working oil port B of the first pressure valve assembly 121. The second oil inlet of the hydraulic lock 208 is the working oil port A of the second pressure valve assembly 122, and the second oil outlet of the hydraulic lock 208 is the working oil port B of the second pressure valve assembly 122. The first shuttle valve 216 is connected to the control oil port of the first pressure valve assembly 121, and the second shuttle valve 217 is connected to the control oil port of the second pressure valve assembly 122. The control ends of both the first shuttle valve 216 and the second shuttle valve 217 are in communication with the third reversing valve 207.

[0047] In this embodiment, a first relief valve 124 and a first pressure gauge 126 are further provided on the first branch oil passage 310 , and a second relief valve 125 and a second pressure gauge 127 are further provided on the second branch oil passage 320 .

[0048] In this embodiment, the main oil circuit 300 is further provided with an unloading valve 202. Unloading valve 202 is a cartridge-type pressure control valve comprising a pressure valve assembly 105, a sixth solenoid reversing valve 106, and a third relief valve 107. The working oil port A of the pressure valve assembly 105 is connected to the main oil circuit 300. The sixth solenoid reversing valve 106 is a two-position, two-way solenoid valve serving as the pilot valve for the pressure valve assembly 105. One oil port of the sixth solenoid reversing valve 106 is connected to the control oil port of the pressure valve assembly 105. The oil inlet of the third relief valve 107 is connected to the oil circuit between the sixth solenoid reversing valve 106 and the pressure valve assembly 105. The other oil port of the sixth solenoid reversing valve 106 and the oil outlet of the third relief valve 107 are connected to the oil tank.

[0049] Furthermore, the main oil circuit 300 is provided with a third pressure gauge 104 , a plug-in one-way valve 108 , a pressure sensor 109 and a fine filter 110 .

[0050] In this embodiment, the hydraulic pump 102 is a fixed displacement pump. Fixed displacement pumps are more easily adapted to achieve the step-by-step adjustment of the hydraulic system's speed and force, making them suitable for harsh environments. They eliminate the need for a complex and costly variable displacement pump, thereby reducing the failure rate of the hydraulic pump and extending the life of the system. Of course, variable displacement pumps may also be employed in other embodiments.

[0051] In this embodiment, the first hydraulic cylinder 128 and the second hydraulic cylinder 129 share a common cylinder head and base. A large-diameter hydraulic cylinder (the second hydraulic cylinder 129) and a small-diameter hydraulic cylinder (the first hydraulic cylinder 128) are connected in parallel to form a twin-rod hydraulic cylinder. When a fixed-displacement pump is used, the on-off combination of the oil holes achieves low speed under heavy loads and high speed under light loads. This eliminates the need for large-scale cylinders and variable displacement pumps, reducing installation space.

[0052] In this embodiment, the first oil chamber of the first hydraulic cylinder 128 and the first oil chamber of the second hydraulic cylinder 129 are rod chambers, while the second oil chamber of the first hydraulic cylinder 128 and the second oil chamber of the second hydraulic cylinder 129 are rodless chambers, but this is not limiting. When the first reversing valve 203 is turned on, the hydraulic reversing valve 123 operates in the left position, oil flows into the rod chamber of the first hydraulic cylinder 128 and oil returns to the rodless chamber of the first hydraulic cylinder 128, and the piston rod of the first hydraulic cylinder 128 retracts. When the second reversing valve 204 is turned on, the hydraulic reversing valve 123 operates in the right position, oil flows into the rodless chamber of the first hydraulic cylinder 128 and oil returns to the rod chamber of the first hydraulic cylinder 128, and the piston rod of the first hydraulic cylinder 128 extends, and the piston rod of the second hydraulic cylinder 129 follows. When the first throttle valve 205 is turned on, oil enters the rod chamber of the second hydraulic cylinder 129 and oil returns to the rodless chamber of the second hydraulic cylinder 129, and the piston rod of the second hydraulic cylinder 129 retracts; when the second throttle valve 206 is turned on, oil enters the rodless chamber of the second hydraulic cylinder 129 and oil returns to the rod chamber of the second hydraulic cylinder 129, and the piston rod of the second hydraulic cylinder 129 extends, and the piston rod of the first hydraulic cylinder 128 follows the movement.

[0053] Furthermore, the first hydraulic cylinder 128 and the second hydraulic cylinder 129 can adopt the form of a fixed cylinder barrel and a moving piston rod, or the form of a fixed piston rod and a moving cylinder barrel. The first hydraulic cylinder 128 and the second hydraulic cylinder 129 also adopt the form of two double-rod hydraulic cylinders in parallel.

[0054] The present invention also relates to a method for controlling a hydraulic system with adjustable speed and force, which is used to control the hydraulic system with adjustable speed and force as described above. The control method comprises:

[0055] When the piston rod of the hydraulic cylinder needs to be extended, when the hydraulic system with adjustable speed and force is lightly loaded, the second oil chamber (rodless chamber) of the first hydraulic cylinder 128 is controlled to flow oil, or the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 is controlled to flow oil; when the hydraulic system with adjustable speed and force is heavily loaded, the second oil chamber (rodless chamber) of the first hydraulic cylinder 128 is controlled to flow oil, or the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 is controlled to flow oil, or the second oil chamber (rodless chamber) of the first hydraulic cylinder 128 and the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 are controlled to flow oil simultaneously;

[0056] When the piston rod of the hydraulic cylinder needs to retract, when the hydraulic system with adjustable speed and force is lightly loaded, the first oil chamber (rod chamber) of the first hydraulic cylinder 128 is controlled to supply oil or the first oil chamber (rod chamber) of the second hydraulic cylinder 129 is controlled to supply oil; when the hydraulic system with adjustable speed and force is heavily loaded, the first oil chamber (rod chamber) of the first hydraulic cylinder 128 is controlled to supply oil or the first oil chamber (rod chamber) of the second hydraulic cylinder 129 is controlled to supply oil, or the first oil chamber (rod chamber) of the first hydraulic cylinder 128 and the first oil chamber (rod chamber) of the second hydraulic cylinder 129 are controlled to supply oil at the same time.

[0057] Specifically, if Figure 3 As shown, when the hydraulic cylinders need to move leftward, meaning the piston rods of both hydraulic cylinders are extended, electromagnet 6Y is energized, and hydraulic oil flows through third reversing valve 207, causing hydraulic lock 208 to conduct in the opposite direction. Under light load, two speeds are selectable: oil flow into the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 or into the second oil chamber (rodless chamber) of the first hydraulic cylinder 128. Taking the second oil chamber (rodless chamber) of the first hydraulic cylinder 128 as an example, electromagnet 3Y is energized, and hydraulic oil flows through second reversing valve 204, driving hydraulic reversing valve 123 to the right position. This forces pressurized oil into the second oil chamber (rodless chamber) of the first hydraulic cylinder 128, rapidly moving the first hydraulic cylinder 128 to the designated position. At this point, the second hydraulic cylinder 129 follows the movement of the first hydraulic cylinder 128, creating a negative pressure in the second oil chamber (rodless chamber) of the second hydraulic cylinder 129, drawing oil from the tank and replenishing it through hydraulic lock 208.

[0058] When heavy loads are applied, the hydraulic cylinder is required to output force. At this time, the hydraulic cylinder can output three types of forces, namely, the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 is filled with oil, the second oil chamber (rodless chamber) of the first hydraulic cylinder 128 is filled with oil, or the second oil chambers (rodless chambers) of the two hydraulic cylinders are filled with oil at the same time. Since the effective area of ​​the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 is large enough, it is usually only necessary to supply oil to the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 to drive the external load. At this time, when the hydraulic pump 102 is in working state, the electromagnet 3Y loses power and the electromagnet 4Y is energized. The pressure oil enters the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 through the first throttle valve 205 and the first pressure valve assembly 121, while the oil in the first oil chamber (rod chamber) of the second hydraulic cylinder 129 passes through the second pressure valve assembly 122 and the second throttle valve assembly 118 and returns to the oil tank. The hydraulically controlled reversing valve 123 is in the middle position, so that the two oil chambers of the first hydraulic cylinder 128 are connected to the oil tank. The first hydraulic cylinder 128 is in a follow-up state, and the hydraulic oil drives the piston of the second hydraulic cylinder 129 to move. The piston rods of the two hydraulic cylinders extend together, realizing the output force of the hydraulic cylinder to overcome the heavy load.

[0059] In the starting or pressure maintaining stage, the electromagnet 1Y is powered, and the other electromagnets are all in the power-off state, the sixth electromagnetic directional valve 106 works in the right position, the control oil port X of the pressure valve assembly 105 is communicated with the oil tank through the sixth electromagnetic directional valve 106, and the output oil of the hydraulic pump 102 flows back to the oil tank through the pressure valve assembly 105 and the sixth electromagnetic directional valve 106, so that the hydraulic pump 102 is started in the no-load state or unloaded.

[0060] The present application also relates to a construction machine comprising the speed and force adjustable hydraulic system described above. The construction machine is for example a press, a tractor, a forming machine, etc. Other structures of the construction machine are well known to those skilled in the art and will not be described here.

[0061] The speed and force adjustable hydraulic system, the control method thereof and the construction machine provided by the present application have the following beneficial effects:

[0062] 1. The speed and force adjustable hydraulic system adopts a double-rod hydraulic cylinder composed of a large-diameter hydraulic cylinder (second hydraulic cylinder) and a small-diameter hydraulic cylinder (first hydraulic cylinder) in parallel, and realizes the step adjustment of the speed and force of the system by the on-off combination of the oil holes thereof in the case of using a fixed displacement pump, thereby achieving the effect of heavy load at low speed and light load at high speed, good synchronization, and applicability to harsh environments.

[0063] 2. The hydraulic system is designed more simply to control the hydraulic double cylinder, has low cost, convenient and flexible control, and is easy to implement.

[0064] 3. The plug-in valve system is adopted, which is convenient for system debugging and updating, has compact structure, high space utilization, small control current, is beneficial to program control of the system, has less leakage, can meet the requirements of pressure maintaining occasions, has strong anti-pollution ability, and is reliable in performance.

[0065] 4. The parallel double hydraulic cylinders (first hydraulic cylinder and second hydraulic cylinder) are respectively controlled by separate circuits, which is convenient and flexible in control; further, the system is provided with an unloading circuit, which is beneficial to reducing the reactive loss and oil source heating during waiting; in addition, outlet throttling speed regulation and hydraulic directional valve are adopted, which improves the stability of the system and adapts to the negative load working condition.

[0066] The speed and force adjustable hydraulic system, the control method thereof and the construction machine provided by the present application are described in detail above, and specific examples are applied in this paper to describe the principles and implementation modes of the present application; the above description of the examples is only used to help understand the method and core idea of the present application; meanwhile, according to the idea of the present application, the specific implementation mode and application range will be changed by those skilled in the art, and the above description should not be understood as a limitation of the present application.

Claims

1. A hydraulic system with adjustable speed and force, comprising an oil tank (101), a hydraulic pump (102) connected to the oil tank (101), and an electric motor (103) driving the hydraulic pump (102), characterized in that: It also includes a hydraulic reversing valve (123), a first reversing valve (203), a second reversing valve (204), a first throttle valve (205), a second throttle valve (206), a first hydraulic cylinder (128), and a second hydraulic cylinder (129); the piston rods of the first hydraulic cylinder (128) and the second hydraulic cylinder (129) are arranged in parallel and move synchronously in the same direction, and the inner diameter of the first hydraulic cylinder (128) is smaller than the inner diameter of the second hydraulic cylinder (129); The hydraulic pump (102) is connected to the first hydraulic cylinder (128) and the second hydraulic cylinder (129) through a main oil circuit (300); wherein, the oil inlet of the hydraulic reversing valve (123) is connected to the main oil circuit (300), the two working oil ports of the hydraulic reversing valve (123) are respectively connected to the first oil chamber and the second oil chamber of the first hydraulic cylinder (128), the oil inlets of the first reversing valve (203) and the second reversing valve (204) are connected to the main oil circuit (300), and the oil outlets of the first reversing valve (203) and the second reversing valve (204) are respectively connected to the main oil circuit (300). The first reversing valve (203) is connected to two hydraulic control ends of the hydraulic reversing valve (123), wherein the first reversing valve (203) includes a first directional valve assembly (111), a second directional valve assembly (112) and a first electromagnetic reversing valve (211), the working oil port B of the second directional valve assembly (112) and the oil inlet port P of the first electromagnetic reversing valve (211) are connected to the main oil circuit (300), and the working oil port A and the working oil port B of the first electromagnetic reversing valve (211) are connected to the control oil port X of the first directional valve assembly (111) and the control oil port X of the second directional valve assembly (112). Port X, the working oil port A of the first directional valve assembly (111) and the working oil port A of the second directional valve assembly (112) are connected to one of the hydraulic control ends of the hydraulic reversing valve (123), the return oil port T of the first solenoid reversing valve (211) and the working oil port B of the first directional valve assembly (111) are connected to the return oil tank; the second reversing valve (204) includes a third directional valve assembly (113), a fourth directional valve assembly (114) and a second solenoid reversing valve (212), the working oil port B of the third directional valve assembly (113) and the working oil port B of the second solenoid reversing valve (212) are connected to the return oil tank; ) is connected to the main oil circuit (300), the working oil port A and the working oil port B of the second electromagnetic reversing valve (212) are respectively connected to the control oil port X of the third directional valve assembly (113) and the control oil port X of the fourth directional valve assembly (114), the working oil port A of the third directional valve assembly (113) and the working oil port A of the fourth directional valve assembly (114) are connected to the other hydraulic control end of the hydraulic reversing valve (123), and the return oil port T of the second electromagnetic reversing valve (212) and the working oil port B of the fourth directional valve assembly (114) are connected to the return oil tank; The oil inlets of the first throttle valve (205) and the second throttle valve (206) are connected to the main oil circuit (300), the oil outlet of the first throttle valve (205) is connected to the second oil chamber of the second hydraulic cylinder (129) through the first branch oil circuit (310), and the oil outlet of the second throttle valve (206) is connected to the first oil chamber of the second hydraulic cylinder (129) through the second branch oil circuit (320).

2. The hydraulic system with adjustable speed and force according to claim 1, characterized in that: The first throttle valve (205) includes a first throttle valve assembly (115), a fifth directional valve assembly (116) and a third electromagnetic reversing valve (213); the working oil port B of the fifth directional valve assembly (116) and the oil inlet port P of the third electromagnetic reversing valve (213) are connected to the main oil circuit (300); the working oil port A and the working oil port B of the third electromagnetic reversing valve (213) are respectively connected to the control oil port X of the first throttle valve assembly (115) and the control oil port X of the fifth directional valve assembly (116); the working oil port A of the first throttle valve assembly (115) and the working oil port A of the fifth directional valve assembly (116) are connected to the second oil chamber of the second hydraulic cylinder (129) through the first branch oil circuit (310); the return oil port T of the third electromagnetic reversing valve (213) and the working oil port B of the first throttle valve assembly (115) are connected to the return oil tank; The second throttle valve (206) includes a sixth directional valve assembly (117), a second throttle valve assembly (118) and a fourth electromagnetic reversing valve (214); the working oil port B of the sixth directional valve assembly (117) and the oil inlet port P of the fourth electromagnetic reversing valve (214) are connected to the main oil circuit (300); the working oil port A and the working oil port B of the fourth electromagnetic reversing valve (214) are respectively connected to the control oil port X of the sixth directional valve assembly (117) and the control oil port X of the second throttle valve assembly (118); the working oil port A of the sixth directional valve assembly (117) and the working oil port A of the second throttle valve assembly (118) are connected to the first oil chamber of the second hydraulic cylinder (129) through the second branch oil circuit (320); the return oil port T of the fourth electromagnetic reversing valve (214) and the working oil port B of the second throttle valve assembly (118) are connected to the return oil tank.

3. The hydraulic system with adjustable speed and force according to claim 1, characterized in that: It also includes a third reversing valve (207) and a hydraulic lock (208); the hydraulic lock (208) has a first oil inlet, a second oil inlet, a first oil outlet, and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil branch path (310), and the second oil inlet and the second oil outlet are located on the second oil branch path (320); the first oil inlet of the hydraulic lock (208) is communicated with the oil outlet of the first throttle valve (205), the first oil outlet of the hydraulic lock (208) is communicated with the second oil chamber of the second hydraulic cylinder (129), the second oil inlet of the hydraulic lock (208) is communicated with the oil outlet of the second throttle valve (206), and the second oil outlet of the hydraulic lock (208) is communicated with the first oil chamber of the second hydraulic cylinder (129).

4. The hydraulic system with adjustable speed and force according to claim 3, characterized in that: The third reversing valve (207) includes a seventh directional valve assembly (119), an eighth directional valve assembly (120) and a fifth solenoid reversing valve (215). The working oil port A of the eighth directional valve assembly (120) and the oil inlet port P of the fifth solenoid reversing valve (215) are connected to the main oil circuit (300). The working oil port A and the working oil port B of the fifth solenoid reversing valve (215) are respectively connected to the control oil port X of the seventh directional valve assembly (119) and the control oil port X of the eighth directional valve assembly (120). The working oil port A of the seventh directional valve assembly (119) and the working oil port B of the eighth directional valve assembly (120) are connected to the hydraulic lock (208). The return oil port T of the fifth solenoid reversing valve (215) and the working oil port B of the seventh directional valve assembly (119) are connected to the return oil tank. The hydraulic lock (208) includes a first pressure valve assembly (1 21), a second pressure valve assembly (122), a first shuttle valve (216) and a second shuttle valve (217), the first oil inlet of the hydraulic lock (208) is the working oil port A of the first pressure valve assembly (121), the first oil outlet of the hydraulic lock (208) is the working oil port B of the first pressure valve assembly (121), the second oil inlet of the hydraulic lock (208) is the working oil port A of the second pressure valve assembly (122), the second oil outlet of the hydraulic lock (208) is the working oil port B of the second pressure valve assembly (122), the first shuttle valve (216) is connected to the control oil port of the first pressure valve assembly (121), the second shuttle valve (217) is connected to the control oil port of the second pressure valve assembly (122), and the control ends of the first shuttle valve (216) and the second shuttle valve (217) are both communicated with the third reversing valve (207).

5. The hydraulic system with adjustable speed and force according to claim 1, characterized in that: The first oil branch circuit (310) is further provided with a first overflow valve (124) and a first pressure gauge (126), and the second oil branch circuit (320) is further provided with a second overflow valve (125) and a second pressure gauge (127).

6. The hydraulic system with adjustable speed and force according to claim 1, characterized in that: The main oil circuit (300) is further provided with an unloading valve (202), the unloading valve (202) comprising a pressure valve assembly (105), a sixth electromagnetic reversing valve (106) and a third overflow valve (107); the main oil circuit (300) is further provided with a third pressure gauge (104), a plug-in check valve (108), a pressure sensor (109) and a fine filter (110); the hydraulic pump (102) is a fixed displacement pump.

7. The hydraulic system with adjustable speed and force according to claim 1, characterized in that: The first hydraulic cylinder (128) and the second hydraulic cylinder (129) share the same cylinder head and cylinder bottom.

8. A method for controlling a hydraulic system with adjustable speed and force, characterized in that: A method for controlling a hydraulic system with adjustable speed and force according to any one of claims 1 to 7, wherein the control method comprises: When the piston rod of the hydraulic cylinder needs to be extended, when the hydraulic system with adjustable speed and force is lightly loaded, the second oil chamber of the first hydraulic cylinder (128) is controlled to be filled with oil, or the second oil chamber of the second hydraulic cylinder (129) is controlled to be filled with oil; when the hydraulic system with adjustable speed and force is heavily loaded, the second oil chamber of the first hydraulic cylinder (128) is controlled to be filled with oil, or the second oil chamber of the second hydraulic cylinder (129) is controlled to be filled with oil, or the second oil chambers of the first hydraulic cylinder (128) and the second oil chambers of the second hydraulic cylinder (129) are controlled to be filled with oil simultaneously; When the piston rod of the hydraulic cylinder needs to be retracted, when the hydraulic system with adjustable speed and force is lightly loaded, the first oil chamber of the first hydraulic cylinder (128) is controlled to be filled with oil, or the first oil chamber of the second hydraulic cylinder (129) is controlled to be filled with oil; when the hydraulic system with adjustable speed and force is heavily loaded, the first oil chamber of the first hydraulic cylinder (128) is controlled to be filled with oil, or the first oil chamber of the second hydraulic cylinder (129) is controlled to be filled with oil, or the first oil chamber of the first hydraulic cylinder (128) and the first oil chamber of the second hydraulic cylinder (129) are controlled to be filled with oil at the same time.

9. An engineering machine, characterized in that: A hydraulic system with adjustable speed and force comprising the hydraulic system as claimed in any one of claims 1 to 7.

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