Double-acting actuator speed switching hydraulic control system

Abstract

The invention discloses a double-acting actuator speed switching hydraulic control system, which aims to solve the problem that the actuator needs to have different movement speeds in one direction and maintain a movement speed in the other direction. The invention is implemented through the following technical scheme: the ring-through valve uses the flow window connecting the oil inlet P and the oil return port R to connect the two-position four-way electromagnetic reversing valve and the two-position three-way electromagnetic reversing valve connected at the far end through a two-way hydraulic pipeline; the two-position four-way electromagnetic reversing valve uses the state conversion valve and the second damping element connected to the hydraulic pipeline of the oil return port R and the actuator to connect the first damping element and the actuator to form an oil circuit; the ring-through valve controls the power on or off of the two-position three-way electromagnetic reversing valve 3 through the two-position four-way electromagnetic reversing valve, controls the working position of the state conversion valve, quickly selects and changes the movement direction and movement speed of the actuator, and realizes the movement speed switching of the oil flow direction and flow size of the actuator.

Description

Technical Field

[0001] The present invention relates to a hydraulic control system mainly used for controlling the speed switching of a double-acting actuator. The actuator has the same movement speed in one direction and two or more movement speeds in the direction opposite to the direction. Background Art

[0002] In the hydraulic system, the actuator refers to the element that converts the pressure energy of the liquid into mechanical energy. It can complete the operations required by the machine, such as "force" and "speed" (the hydraulic cylinder is an actuator that converts the pressure energy into reciprocating linear motion, so the output force and speed), such as "torque" and "speed". The hydraulic motor inputs hydraulic oil, and the actuator that converts the hydraulic oil into continuous rotational motion, so the output is torque and speed. The power element converts the mechanical energy of the prime mover into the pressure energy of the liquid. The oil pump actuator in the hydraulic system, such as the hydraulic cylinder and the hydraulic motor, increases, decreases, advances, retreats, rotates, and performs various actions. The hydraulic oil pump provides liquid power to control the hydraulic oil to enter the hydraulic cylinder through the hydraulic valve to realize the reciprocating motion of the hydraulic cylinder. In modern hydraulic systems, it is often necessary for the actuator to have different movement speeds under different working conditions to realize various functions of the hydraulic system. The speed adjustment of the actuator of the hydraulic system and the change of the movement direction are achieved through the control valve. Since pressure depends on load and speed depends on flow, the slower speed means the flow reaching the actuator becomes smaller. If the pump is severely worn, the volumetric efficiency is reduced, the leakage is large, and the output flow becomes smaller. If the flow valve is abnormal, the oil flows back to the oil tank from the overflow valve, resulting in a smaller flow reaching the actuator. If the control valve is worn, the gap is large and the valve core has a large leakage when the wear is serious. When the actuator itself is not well sealed, the oil leaks, and there are impurities in the sealing ring that affect the operation of the valve. The flow control valve adjusts the valve port flow by changing the valve port flow area, thereby controlling the movement of the actuator. Among the hydraulic control valves, the pressure control valve can change the speed of the actuator movement. It is common for equipment to shut down due to a hydraulic cylinder failure. When the flow valve or directional valve core is stuck or the valve hole is blocked, the hydraulic cylinder is prone to malfunction or malfunction. The piston rod is stuck with the cylinder barrel or the hydraulic cylinder is blocked. At this time, no matter how it is operated, the hydraulic cylinder will not move or move very little. When the control pressure of the hydraulic system is too low, the throttling resistance in the control pipeline may be too large, the flow valve is improperly adjusted, the control pressure is inappropriate, and the pressure source is disturbed. Under low temperature conditions, the viscosity of the hydraulic oil is high and the fluidity is poor, resulting in slow movement of the hydraulic cylinder. The servo control system is mainly manifested by inaccurate piston rod stop, insufficient thrust, speed reduction, unstable operation, etc., the reason is internal leakage of the hydraulic cylinder. Internal leakage of the hydraulic cylinder includes leakage caused by excessive wear of the hydraulic cylinder body seal, piston rod and sealing cover seal, and piston seal. The internal parts of the hydraulic cylinder are deformed, worn, or the shape and position tolerances exceed the limit, and the action resistance is too large, so that the speed of the hydraulic cylinder piston changes with the different stroke positions, slipping or creeping occurs, the resistance increases, and the speed decreases. The circuit that controls the movement speed of the actuator by controlling the flow of the medium is divided into a speed control circuit and a direction control circuit according to different functions.The speed control circuit is used to control the movement speed of a single actuator. The throttle valve or speed control valve can be used to control the flow. The throttle valve controls the flow of the hydraulic pump into the hydraulic cylinder (the excess flow flows back to the oil tank through the relief valve), thereby controlling the movement speed of the hydraulic cylinder. This form is called throttling speed control. In the speed control circuit, as the load increases, the hydraulic pump and hydraulic motor leak, so the speed changes. In the throttling speed control circuit, a large amount of oil overflows back to the oil tank from the relief valve, which is the main reason for large energy loss, temperature rise and low efficiency. The pressure regulating circuit sets and limits the maximum working pressure of the hydraulic system, or enables the actuator to achieve multi-stage pressure conversion at different stages of the working process. Generally, an overflow valve is used to achieve this function. Generally, an overflow valve is used to achieve this function. The direction control circuit is a circuit that controls the flow direction of the hydraulic medium. The circuit that uses a directional control valve to control the movement direction of a single actuator so that it can move in the forward and reverse directions or stop is called a reversing circuit. When the actuator stops, the circuit that prevents the actuator from moving due to leakage caused by external factors such as load is called a locking circuit. The hydraulic cylinder is an actuator that realizes linear reciprocating motion and is an element that converts the pressure energy of the fluid into mechanical energy. It drives the mechanism to perform linear reciprocating motion, with pressure and flow as input and force and speed as output. Movement in one direction is achieved by hydraulic force, and the movement in the other direction is achieved by spring force, gravity, etc.; the movement in both directions of the double-acting hydraulic cylinder is achieved by hydraulic force; but the volume and weight are large, the torque pulsates, and the low-speed stability is poor. In practical applications, the hydraulic system often changes the oil circuit connection of the single-rod cylinder through a control valve to make it have different working modes, thereby obtaining a fast-forward (differential continuous oil inlet) working cycle. When the hydraulic cylinder is at high speed and heavy load, the speed is greatly affected by load changes, that is, when the hydraulic cylinder of the circuit is at high speed and heavy load, the speed is greatly affected by load changes, and the speed rigidity is poor; the oil inlet throttling speed control circuit has both overflow loss and throttling loss, and the circuit efficiency is low; the speed is greatly affected by load changes, and the circuit has different maximum load-bearing capacities under different throttle valve flow areas. The speed regulation range of the circuit is limited. In the throttle valve speed regulation circuit, when the load changes, the pressure difference before and after the throttle valve changes, and the flow through the throttle valve changes, so the speed load characteristics of the circuit are relatively poor. The return oil chamber pressure of the return oil throttling speed regulation circuit is relatively high, especially when the load is close to zero, the pressure is higher, which affects the safety, sealing and life of the return oil pipe. In the differential circuit, the flow of the pump and the flow discharged from the rod chamber of the cylinder are combined. The valves and pipes passing through should be selected according to the composite flow, otherwise it will cause excessive pressure loss and the oil supply pressure will be too high when the pump is unloaded.Usually the speed switching circuit is used to switch the speed of the actuator. The switching process is required to be smooth and the switching accuracy is high. According to the speed before and after the switching, there is a switching between fast-working speed or two working speeds. The switching circuit of the fast motion and working feed uses the speed switching circuit of the stroke valve. The reversing valve works in the right position, and the hydraulic cylinder piston moves quickly to the predetermined position. Sometimes the pipeline needs to be connected very long, and the pressure loss is large. At the moment of speed switching, it will cause the feed component to rush forward suddenly. The circuit that starts, stops or changes the direction of movement of the actuator is called the direction control circuit. Commonly used directional control circuits are: reversing circuit, locking circuit, and braking circuit. The reversing circuit uses a two-position four-way reversing valve and a three-position four-way reversing valve to make the double-acting hydraulic cylinder reversing. The two-position valve can only make the actuator move forward and reverse, and the three-position valve has a neutral function. The neutral function relies on the single-acting hydraulic cylinder that returns by spring or gravity to achieve automatic reciprocating motion, but due to the leakage of the neutral function slide valve, the piston cannot remain in the stop position for a long time, so the locking accuracy is not high. For occasions with large flow and high requirements for switching stability, the reversing circuit of the electromagnetic reversing valve can no longer adapt. For frequent and continuous reciprocating motion, a manual reversing valve or a motorized reversing valve is often used as a pilot valve, or a reversing circuit of an electro-hydraulic reversing valve is used. The reversing circuit using a hydraulic reversing valve is mainly used in occasions where the working parts move at a high speed and the reversing accuracy is not required. Pressure shock or fluctuation in the pipeline will cause malfunction. This circuit is suitable for occasions where the number of actuators is small and the load changes little. When an oil source supplies oil to multiple actuators, each actuator is restrained in action due to the mutual influence of pressure and flow in the circuit. Summary of the invention

[0003] The purpose of the present invention is to address the shortcomings of the prior art and to provide a double-acting actuator speed switching hydraulic control valve system with high efficiency, smooth speed switching process, accurate switching point position, and the ability to solve the problem that the actuator needs to have different movement speeds in one direction and maintain one movement speed in the other direction.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a double-acting actuator speed switching hydraulic control system, comprising: a ring-through valve bidirectionally connecting the actuator through a hydraulic pipeline, characterized in that: the ring-through valve uses a flow window connecting an oil inlet P and an oil return port R to connect a two-position four-way electromagnetic reversing valve and a two-position three-way electromagnetic reversing valve connected at a remote end through a bidirectional hydraulic pipeline, the two-position four-way electromagnetic reversing valve uses a bidirectional hydraulic pipeline to respectively connect a state conversion valve and a second damping element connected to the hydraulic pipeline of the oil return port R and communicating with the actuator; the state conversion valve connects the first damping element and the actuator respectively through a bidirectional hydraulic pipeline; the ring-through valve connects the oil inlet P and the oil return port R, controls the power on or off of the two-position three-way electromagnetic reversing valve, controls the working position of the state conversion valve, quickly selects and changes the movement direction and movement speed of the actuator, and realizes the movement speed switching of the oil flow direction and flow rate of the actuator.

[0005] Compared with the prior art, the present invention has the following beneficial effects: high efficiency. The present invention adopts a two-position four-way electromagnetic reversing valve to use a two-way hydraulic pipeline to respectively connect the state conversion valve and the second damping element connected to the hydraulic pipeline of the oil return port and the actuator; the first damping element and the actuator are respectively connected through the two-way hydraulic pipeline of the state conversion valve, and the hydraulic control valve has small overflow loss and high efficiency. It overcomes the defects that the speed of the hydraulic cylinder is greatly affected by load changes and the speed rigidity is poor when the hydraulic cylinder is at high speed and heavy load; the overflow loss of the oil inlet throttling speed control circuit is large, the circuit efficiency is low, and the speed is greatly affected by load changes.

[0006] The speed switching process is smooth. The present invention uses the power on and off of the two-position four-way electromagnetic reversing valve to control the working position of the state conversion valve, controls the size of the outflow flow of the actuator, and quickly selects and changes the movement direction and speed of the actuator by controlling the power on and off of the electromagnetic reversing valve. The speed switching is smooth, the switching point position is accurate, and the speed stability is better than that of the volume speed control circuit.

[0007] The present invention controls the oil flow direction of the actuator by the on / off control state of the two-position three-way electromagnetic reversing valve. A one-way damping valve is respectively arranged at the oil inlet and oil return parts of the actuator to change the size of the oil flow out of the actuator to realize the principle scheme of the hydraulic control valve in which the actuator moves at different speeds in one direction and maintains another movement speed in the other direction. The problem that the actuator needs to have different movement speeds in one direction and maintain one movement speed in the other direction is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the principle of the speed switching hydraulic control system of the double-acting actuator of the present invention.

[0009] In the figure: 1 is a ring-through valve, 2 is a two-position four-way directional control valve, 3 is a two-position three-way electromagnetic directional control valve, 4 is a state switching valve, 5 is a first damping element, 6 is a second damping element, and 7 is an actuator.

[0010] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the scope of the embodiments described. All these concepts should be regarded as the protection scope of the content disclosed in this technology. DETAILED DESCRIPTION

[0011] See also Figure 1 In the preferred embodiment described below, a double-acting actuator speed switching hydraulic control system includes: a ring-through valve 1 bidirectionally connected to the actuator 7 through a hydraulic pipeline. The ring-through valve 1 uses a flow window connecting the oil inlet P and the oil return port R to connect the two-position four-way electromagnetic reversing valve 2 and the two-position three-way electromagnetic reversing valve 3 connected at the far end through a bidirectional hydraulic pipeline. The two-position four-way electromagnetic reversing valve 2 uses a bidirectional hydraulic pipeline to respectively connect the state conversion valve 4 and the second damping element 6 connected to the hydraulic pipeline of the oil return port R and the actuator 7; the state conversion valve 4 connects the first damping element 5 and the actuator 7 through a bidirectional hydraulic pipeline; the ring-through valve 1 connects the oil inlet P and the oil return port R, controls the power on or off of the two-position three-way electromagnetic reversing valve 3, controls the working position of the state conversion valve 4, quickly selects and changes the movement direction and movement speed of the actuator 7, and realizes the movement speed switching of the oil flow direction and flow rate of the actuator 7.

[0012] The two-position four-way solenoid reversing valve 2 controls the working position of the state conversion valve 4. The right end of the state conversion valve 4 is connected to the oil return port R, and the left end of the state conversion valve 4 is controlled by the on and off of the two-position three-way solenoid reversing valve 3. When the two-position three-way solenoid reversing valve 3 is powered on, the two-position three-way solenoid reversing valve 3 works in the right position, the oil inlet P is connected to the two-position three-way solenoid reversing valve 3 through the flow window of the ring valve 1, and the pressure oil is connected to the left end of the state conversion valve 4 through the right position of the two-position three-way solenoid reversing valve 3. The liquid pressure at the left end of the state conversion valve 4 overcomes the spring force at its right end, so that the state conversion valve 4 works in the left position; when the two-position three-way solenoid reversing valve 3 is powered off, the two-position three-way solenoid reversing valve 3 works in the left position, and the oil inlet P is connected to the left position of the two-position three-way solenoid reversing valve 3 through the flow window of the ring valve 1. At this time, the pressure oil is sealed by the left position of the two-position three-way solenoid reversing valve 3. The oil return port R is connected to the left position of the two-position three-way electromagnetic reversing valve 3 through the flow window of the annular valve 1 and is connected to the left end of the state conversion valve 4. The liquid pressure at the left end of the state conversion valve 4 cannot overcome the spring force at its right end, so that the state conversion valve 4 works in the right position.

[0013] The two-position four-way solenoid reversing valve 2 and the two-position three-way solenoid reversing valve 3 are connected to the hydraulic pipe of the oil return port R and are connected in parallel in the hydraulic oil circuit. By controlling the power on and off of the two-position three-way solenoid reversing valve 3, the working state of the variable state conversion valve 4 is switched to change the movement direction of the actuator 7. The state conversion valve 4 controls the oil flowing out of the left cavity of the actuator 7 to generate damping or not and the flow rate of the oil flowing out of the left cavity through the first damping element 5 connected to the left cavity of the actuator 7, thereby realizing the switching of the movement speed of the actuator 7.

[0014] The two-position four-way solenoid directional valve 2 is connected to the second damping element 6 on the hydraulic pipeline between the oil return port R of the annular valve 1 and the actuator 7, and uses the second damping element 6 to generate damping for the oil flowing out of the right chamber connected to the actuator 7.

[0015] When the pressure of the oil inlet P of the ring-through valve 1 is zero, the ring-through valve 1 is bidirectionally connected to the actuator 7 through the hydraulic pipeline. When the pressure of the oil inlet P is the rated oil supply pressure, the right end of the ring-through valve 1 is connected to the oil inlet P. Under the action of the left end spring force and the oil inlet P, the ring-through valve 1 works in the right position. The actuator 7 moves quickly to the left end and slowly to the right end. The fluid from the pressure source passes through the oil window of the valve core of the ring-through valve 1 to connect the oil inlet P hydraulic pipeline to the two-position three-way electromagnetic reversing valve 3, so that the two-position three-way electromagnetic reversing valve 3 is always powered off, at this time, the electromagnetic reversing valve 3 works in the left position, and the pressure oil cannot enter the electromagnetic reversing valve 3; at the same time, the two-position four-way electromagnetic reversing valve 2 is powered off, at this time, the two-position four-way electromagnetic reversing valve 2 works in the left position function, at this time, the two-position four-way electromagnetic reversing valve 2 connected in parallel with the two-position three-way electromagnetic reversing valve 3 connects the hydraulic pipeline of the oil inlet P with the state conversion valve 4 through the flow window of its valve core, and both ends of the state conversion valve 4 are connected with the return oil port R. Under the action of the spring force, the state conversion valve 4 works in the right position function. The oil inlet P is connected to the left chamber of the actuator 7 through the two-position four-way electromagnetic reversing valve 2 and the state conversion valve 4. The actuator 7 moves to the right under the action of the pressure oil. The oil in the right chamber of the actuator 7 has two oil paths to return to the oil return port R. One oil path passes through the ring valve 1. Because the ring valve 1 works in the right position, the oil path is blocked; therefore, the oil in the right chamber of the actuator 7 can only be connected to the oil return port R through the second damping element 6 and the two-position four-way electromagnetic reversing valve 2. In this circuit, there is no throttling when the pressure oil enters the actuator 7. When the pressure oil flows out of the actuator 7, it passes through the second damping element 6, throttling occurs, and the actuator 7 moves slowly to the right end. When the actuator 7 moves to the left end, the two-position three-way solenoid reversing valve 3 is always powered off, and the two-position four-way solenoid reversing valve 2 is always powered on. At this time, the two-position four-way solenoid reversing valve 2 works in the right position; the oil inlet P connects to the right position of the two-position four-way solenoid reversing valve 2, and the pressure oil flows through the valve core flow window of the right position of the two-position four-way solenoid reversing valve 2 into the second damping element 6, and then enters the right chamber of the actuator 7. The oil in the left chamber of the actuator 7 reaches the state conversion valve 4 through two oil paths, one is directly reached through the pipeline, and the other is reached through the first damping element 5. Because the state conversion valve 4 works in the right position, the oil in the left chamber of the actuator 7 can only enter the right position of the state conversion valve 4 through the pipeline, and the oil flows through the flow window of the right position valve core of the state conversion valve 4 into the right position of the two-position four-way solenoid reversing valve 2, and the oil flows to the return oil port R through the pipeline. In this circuit, there is no throttling when the pressure oil enters the right chamber of the actuator 7, and there is no throttling when the pressure oil flows out of the actuator 7, and the actuator 7 moves quickly to the left end.

[0016] The implementation method of the actuator 7 moving slowly to the left and right ends is as follows: the two-position three-way electromagnetic reversing valve 3 is always energized, at which time the two-position three-way electromagnetic reversing valve 3 works in the right position, and the oil inlet P is connected to the two-position three-way electromagnetic reversing valve 3; the oil inlet P is connected to the left end of the state conversion valve 4 through the valve core flow window of the two-position three-way electromagnetic reversing valve 3, and the right end of the state conversion valve 4 is connected to the return oil port R, and the liquid pressure at the left end of the state conversion valve 4 overcomes the spring force at its right end, so that the state conversion valve 4 works in the left position; at the same time, the two-position four-way electromagnetic reversing valve 2 is de-energized, and at this time the two-position four-way electromagnetic reversing valve 2 works in the left position function. The circulation route of the pressure oil is as follows: the pressure oil enters the oil inlet P, passes through the flow window of the valve core of the right position function of the ring valve, and enters the two-position four-way electromagnetic reversing valve 2 and the two-position three-way electromagnetic reversing valve 3 at the same time, and the two-position four-way electromagnetic reversing valve 2 and the two-position three-way electromagnetic reversing valve 3 are connected in parallel.

[0017] The pressure oil enters the left position of the state conversion valve 4 through the flow window of the left position valve core of the two-position four-way solenoid reversing valve 2, and enters the first damping element 5 through the flow window of the left position valve core of the state conversion valve 4, and enters the left chamber of the actuator 7 through the flow window of the first damping element 5. The oil in the right chamber of the actuator 7 enters the left position of the two-position four-way solenoid reversing valve 2 through the flow window of the second damping element 6, and the pressure oil flows through the flow window of the left position valve core of the two-position four-way solenoid reversing valve 2 to the return oil port R. In this return oil circuit, the oil entering the right chamber of the actuator 7 is damped when passing through the first damping element 5, and the oil in the right chamber of the actuator 7 is throttled through the second damping element 6 when it flows out, so the actuator 7 moves slowly to the right end. Then the two-position four-way solenoid reversing valve 2 is energized, and at this time, the two-position four-way solenoid reversing valve 2 works in the right position function. The flow route of the pressure oil is as follows: the pressure oil enters the oil inlet P, passes through the flow window of the right position functional valve core of the ring valve, and enters the two-position four-way electromagnetic reversing valve 2 and the two-position three-way electromagnetic reversing valve 3 at the same time. The two-position four-way electromagnetic reversing valve 2 and the two-position three-way electromagnetic reversing valve 3 are connected in parallel. The pressure oil enters the second damping element 6 through the flow window of the right position valve core of the two-position four-way electromagnetic reversing valve 2, and enters the right chamber of the actuator 7 through the flow window of the second damping element 6. There are two oil routes for the oil in the left chamber of the actuator 7 to reach the state conversion valve 4, one is directly reached through the pipeline, and the other is reached through the first damping element 5. Because the state conversion valve 4 works in the left position, the oil in the left chamber of the actuator 7 can only enter the left position of the state conversion valve 4 through the flow window of the first damping element 5, and the oil flows through the flow window of the left position valve core of the state conversion valve 4 to enter the right position of the two-position four-way electromagnetic reversing valve 2, and the oil flows to the return oil port R through the pipeline. In the oil return path, the oil entering the right chamber of the actuator 7 is undamped, and the oil flowing out of the left chamber of the actuator 7 is throttled by the first damping element 5, so the actuator 7 moves slowly to the left end.

[0018] When the system is not pressurized, the ring-through valve 1 always works in the left position under the action of its spring force. At this time, the left and right chambers of the actuator 7 communicate with each other through the ring-through valve and are connected to the system return oil.

[0019] The above is a preferred embodiment of the present invention. It should be noted that the above embodiment is for illustration of the present invention, but the present invention is not limited thereto, and those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. For those of ordinary skill in the art, various modifications and improvements may be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A double-acting actuator speed switching hydraulic control system, comprising: A loop-through valve (1) bidirectionally connected to an actuator (7) via a hydraulic pipeline is characterized in that: the loop-through valve (1) utilizes a flow window connected to an oil inlet P and an oil return port R to connect a two-position four-way electromagnetic reversing valve (2) and a two-position three-way electromagnetic reversing valve (3) connected at a remote end via a bidirectional hydraulic pipeline; the two-position four-way electromagnetic reversing valve (2) utilizes a bidirectional hydraulic pipeline to connect a state conversion valve (4) and a second damping element (6) connected to the hydraulic pipeline of the oil return port R and connected to the actuator (7); the state conversion valve (4) connects a first damping element (5) and the actuator (7) via a bidirectional hydraulic pipeline; the loop-through valve (1) connects the oil inlet P and the oil return port R, controls the working position of the state conversion valve (4) by controlling the power on or off of the two-position three-way electromagnetic reversing valve (3), quickly selects and changes the movement direction and movement speed of the actuator (7), and realizes the movement speed switching of the oil flow direction and flow rate of the actuator (7).

2. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The right end of the state conversion valve (4) is connected to the oil return port R, and the left end controls the working position of the state conversion valve (4) by turning on and off the power of the connected two-position three-way electromagnetic reversing valve (3). The two-position three-way electromagnetic reversing valve (3) is energized, and the two-position three-way electromagnetic reversing valve (3) works in the right position. The oil inlet P is connected to the two-position three-way electromagnetic reversing valve (3) through the flow window of the annular valve (1). The oil inlet P is connected to the left end of the state conversion valve (4) through the right position of the two-position three-way electromagnetic reversing valve (3). The hydraulic pressure at the left end of the state conversion valve (4) overcomes the spring force at the right end, so that the state conversion valve (4) works in the left position.

3. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The two-position three-way electromagnetic reversing valve (3) is powered off, the two-position three-way electromagnetic reversing valve (3) works in the left position, the oil inlet P is connected to the left position of the two-position three-way electromagnetic reversing valve (3) through the flow window of the ring-through valve (1), the oil inlet P is sealed by the left position of the two-position three-way electromagnetic reversing valve (3), the oil return port R is connected to the left position of the two-position three-way electromagnetic reversing valve (3) through the flow window of the ring-through valve (1), and is connected to the left end of the state conversion valve (4), the hydraulic pressure at the left end of the state conversion valve (4) cannot overcome the spring force at its right end, so that the state conversion valve (4) works in the right position.

4. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: A two-position four-way electromagnetic reversing valve (2) and a two-position three-way electromagnetic reversing valve (3) are connected in parallel in a hydraulic oil circuit. The two-position four-way electromagnetic reversing valve (2) in the oil circuit changes the movement direction of the actuator (7) by controlling its power on and off. The state conversion valve (4) controls the oil flowing out of the left chamber of the actuator (7) to generate damping or not generate damping, and controls the flow rate of the oil flowing out of the left chamber of the actuator (7) to achieve the switching of the movement speed of the actuator (7). The first damping element (5) and the second damping element (6) generate damping for the oil entering or flowing out of the actuator (7). The first damping element (5) is connected in series with the left chamber of the actuator (7), and the second damping element (6) is connected in series with the right chamber of the actuator (7).

5. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The two-position four-way solenoid reversing valve (2) and the two-position three-way solenoid reversing valve (3) are connected to the hydraulic pipe of the oil return port R and are connected in parallel in the hydraulic oil circuit. By controlling the on and off of the two-position three-way solenoid reversing valve (3), the working state of the variable state conversion valve (4) is switched to change the movement direction of the actuator (7). The state conversion valve (4) controls the oil flowing out of the left chamber of the actuator (7) to generate damping or not generate damping and the flow rate of the oil flowing out of the left chamber through the first damping element (5) connected to the left chamber of the actuator (7), thereby realizing the switching of the movement speed of the actuator (7).

6. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The two-position four-way solenoid directional control valve (2) is connected to a second damping element (6) on a hydraulic pipeline between an oil return port R of the ring-through valve (1) and an actuator (7) by bypassing the second damping element (6) to generate damping for oil flowing out of the right chamber connected to the actuator (7).

7. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: When the pressure at the oil inlet P of the ring-through valve (1) is zero, the ring-through valve (1) is bidirectionally connected to the actuator (7) through the hydraulic pipeline. When the pressure at the oil inlet P reaches the rated oil supply pressure, the right end of the ring-through valve (1) is connected to the oil inlet P. Under the action of the spring force at the left end and the oil inlet P, the ring-through valve (1) works in the right position.

8. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The actuator (7) moves quickly to the left end and slowly to the right end. The fluid from the pressure source passes through the oil flow window of the valve core of the ring valve (1) to connect the hydraulic pipeline of the oil inlet P to the two-position three-way solenoid reversing valve (3), so that the two-position three-way solenoid reversing valve (3) is always powered off. The two-position three-way solenoid reversing valve (3) works in the left position and the pressure oil cannot enter the two-position three-way solenoid reversing valve (3). The two-position four-way solenoid reversing valve (2) is powered off. The two-position four-way solenoid reversing valve (2) works in the left position. The two-position four-way solenoid reversing valve (2) connected in parallel with the two-position three-way solenoid reversing valve (3) connects the hydraulic pipeline of the oil inlet P to the state conversion valve (4) through the flow window of its valve core. The two ends of the state conversion valve (4) are connected to the oil return port R. Under the action of the spring force, the state conversion valve (4) works in the right position.

9. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: The oil inlet P is connected to the left chamber of the actuator (7) through the two-position four-way electromagnetic reversing valve (2) and the state conversion valve (4). The actuator (7) moves to the right under the action of the pressure oil. The oil in the right chamber of the actuator (7) returns to the oil return port R through two hydraulic circuits. One oil circuit passes through the annular valve (1), and the other is connected to the oil return port R through the second damping element (6) and the two-position four-way electromagnetic reversing valve (2).

10. The double-acting actuator speed switching hydraulic control system according to claim 1, characterized in that: When the actuator (7) moves to the left, the two-position three-way solenoid reversing valve (3) is always powered off, and the two-position four-way solenoid reversing valve (2) is always powered on. At this time, the two-position four-way solenoid reversing valve (2) works in the right position; the oil inlet P is connected to the right position of the two-position four-way solenoid reversing valve (2), and the pressure oil flows through the valve core flow window of the right position of the two-position four-way solenoid reversing valve (2) into the second damping element (6), and then enters the right chamber of the actuator (7). The oil in the left chamber of the actuator (7) reaches the state conversion valve (4) through two oil paths, one directly through the pipeline, and the other through the first damping element (5).

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