A large-flow anti-air suction hydraulic drive circuit with differential function

Abstract

The present invention relates to a large-flow anti-void hydraulic drive circuit with differential function, which includes an electro-hydraulic reversing valve, a shuttle valve, a displacement sensor, an oil cylinder, a simulated load, a differential valve, an oil tank and a back-pressure valve; the electro-hydraulic reversing valve, the rodless cavity of the oil cylinder and the differential valve are connected in sequence; the displacement sensor is arranged on one side of the oil cylinder; the simulated load is connected to the outer end of the piston rod of the oil cylinder; the left oil port of the shuttle valve is communicated with the rodless cavity of the oil cylinder, and the right oil port is communicated with the rod-end cavity of the oil cylinder; the electro-hydraulic reversing valve is connected to the main oil circuit and the middle oil port of the shuttle valve; the oil tank is connected to the electro-hydraulic reversing valve through the back-pressure valve. By designing the displacement sensor, the back-pressure valve and the shuttle valve, the present invention avoids the problem of air suction in the oil inlet circuit during the switching moment and the problem of misclosing of the electro-hydraulic reversing valve caused by slight air suction due to other unpredictable factors, reduces hydraulic shock, has both the function of differential fast working feed, and also prevents the occurrence of air suction problem in the main oil circuit to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control, and particularly to a large-flow anti-voiding hydraulic drive circuit with a differential function. Background Art

[0002] Hydraulic drive technology is commonly used in various industrial equipment such as machine tools, injection molding machines, and die casting machines due to its advantages of high power density and stepless speed change. R & D personnel often design a differential circuit to meet the needs of the rapid forward working condition of the machine. There are various forms of existing differential circuits, but in the existing differential circuits, there is little research on the circuit for preventing the voiding problem in the rodless cavity when the oil cylinder switches from the differential state to the non-differential state under a large inertia load. Summary of the Invention

[0003] Aiming at the above problems, the purpose of the present invention is to provide a large-flow anti-voiding hydraulic drive circuit with a differential function, which not only has the function of differential rapid forward movement, but also prevents the voiding problem of the main oil circuit to a certain extent, and improves the action stability of the oil cylinder.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A large-flow anti-voiding hydraulic drive circuit with a differential function proposed by the present invention includes an electro-hydraulic directional valve, a shuttle valve, a displacement sensor, an oil cylinder, a simulated load, a differential valve, an oil tank, and a back pressure valve; the electro-hydraulic directional valve, the oil cylinder, and the differential valve are connected in sequence; the displacement sensor is arranged on one side of the oil cylinder; the simulated load is connected to the outer end of the piston rod of the oil cylinder; the left oil port of the shuttle valve is communicated with the rodless cavity of the oil cylinder, and the right oil port is communicated with the rod-end cavity of the oil cylinder; the electro-hydraulic directional valve is connected to the main oil circuit and the middle oil port of the shuttle valve; the oil tank is connected to the electro-hydraulic directional valve through the back pressure valve.

[0006] Further, the electro-hydraulic directional valve is a pilot-operated control valve, its pilot stage is an electromagnetic directional valve, the main valve stage is a hydraulically controlled directional valve, and the control mode is internal control and external leakage type; the X port of the pilot valve of the electro-hydraulic directional valve is connected to the main oil circuit and the middle oil port of the shuttle valve; the pilot control oil enters the control cavity of the main valve of the electro-hydraulic directional valve, causing the electro-hydraulic directional valve to act and realizing the flow-through function.

[0007] Further, the differential valve is a two-position four-way electro-hydraulic directional valve, the control oil of its pilot stage comes from the main oil circuit, and the pilot control oil circuit is connected to the main oil circuit and the rod-end cavity of the oil cylinder through a three-way interface, and the rod-end cavity of the oil cylinder is connected to the three-way interface through a second pipeline; the pilot control oil returns to the oil tank; when the pilot-stage electromagnet is energized, under the pressure of the control oil, the differential valve spool acts, and the oil returning from the rod-end cavity passes through the A→P flow path of the differential valve and is connected to the oil entering the rodless cavity, realizing the large-flow differential function and meeting the working condition requirements of rapid forward movement.

[0008] Furthermore, the back pressure valve is a pilot-operated control valve placed in the return oil circuit. After the oil in the return oil circuit flows out from the T port of the electro-hydraulic directional valve, it enters the lower oil port of the back pressure valve through the internal flow passage of the valve block, and then enters the fuel tank through the outlet beside the back pressure valve. The outlet of the back pressure valve is connected to the fuel tank through the third pipeline; the pilot stage of the back pressure valve is an electromagnetic directional valve, and the main valve stage is a cartridge valve. After the pilot stage electromagnet is energized, the opening of the main valve stage decreases, the back pressure in the return oil circuit increases, and the oil cylinder decelerates.

[0009] Furthermore, the displacement sensor monitors the position of the oil cylinder in real time and sends a signal to the controller to control the electromagnet of the back pressure valve to be energized when the oil cylinder moves to the set position.

[0010] Furthermore, the shuttle valve is a logic control valve. Its left oil port communicates with the rodless cavity of the oil cylinder, its right oil port communicates with the rod chamber of the oil cylinder, and its middle oil port communicates with the pilot stage X port of the electro-hydraulic directional valve.

[0011] Furthermore, the fuel tank is an open fuel tank, which plays the role of storing oil and dissipating heat in the system.

[0012] Furthermore, the rodless cavity of the oil cylinder is connected to the working oil port A of the hydraulic control directional valve; the rod chamber of the oil cylinder is connected to the working oil port A of the differential valve; the P port of the differential valve is connected to the rodless cavity of the oil cylinder through the internal flow passage of the valve block via the first pipeline; the T port of the differential valve is connected to the B port of the hydraulic control directional valve.

[0013] Furthermore, the first pipeline, the second pipeline, and the third pipeline are all high-pressure resistant hoses.

[0014] Compared with the prior art, the large-flow anti-cavitation hydraulic drive circuit with differential function proposed by the present invention, which introduces a displacement sensor, a back pressure valve, and a shuttle valve, has the following beneficial effects:

[0015] (1) It can not only meet the working condition requirements of differential fast feed, but also effectively solve the problem of main oil circuit cavitation caused by the switching of the oil cylinder from differential to non-differential action in the traditional differential circuit, and effectively improve the action stability of the oil cylinder.

[0016] (2) When the back pressure valve responds slowly due to unpredictable factors, resulting in slight cavitation in the rodless cavity of the oil cylinder, the introduction of the shuttle valve can make the control oil pressure at the X port of the electro-hydraulic directional valve 1a not zero, avoiding misclosing of the electro-hydraulic directional valve, playing an "insurance" role, extending the service life of hydraulic components, and reducing hydraulic shock. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural principle diagram of a large-flow anti-cavitation hydraulic drive circuit with differential function proposed by the present invention;

[0018] Figure 2 is the detailed symbolic schematic diagram of the differential valve in the present invention;

[0019] Figure 3 is the schematic diagram of the cylinder movement including differential and non-differential actions;

[0020] Figure 4 is the schematic diagram of the simulation model of the back pressure valve and the simulation curve of its working characteristics;

[0021] Figure 5 is the schematic diagram of the overall simulation model of the drive circuit of the present invention;

[0022] Figure 6 is the model of the displacement sensor control module and the internal algorithm setting interface in the present invention;

[0023] Figure 7 is the schematic diagram of the comparison of the main oil circuit pressure curves between the ordinary oil circuit and the oil circuit of the present invention when switching from differential to non-differential action;

[0024] Figure 8 is the model of the shuttle valve control oil circuit and the schematic diagram showing that the pilot control oil pressure of the electro-hydraulic directional valve is not zero due to the existence of the shuttle valve control oil circuit after the occurrence of the unpredictable cavitation phenomenon;

[0025] Figure 9 is the schematic diagram of the comparison of whether the spool of the electro-hydraulic directional valve in the ordinary oil circuit and the oil circuit of the present invention malfunctions after the occurrence of the unpredictable cavitation phenomenon.

[0026] Among them, reference numerals: 1 - electro-hydraulic directional valve; 2 - shuttle valve; 3 - displacement sensor; 4 - cylinder; 5 - simulated load; 6 - differential valve; 7 - oil tank; 8 - back pressure valve; 9 - first pipeline; 10 - second pipeline; 11 - third pipeline; 1a - pilot valve of electro-hydraulic directional valve; 1b - main valve of electro-hydraulic directional valve; 4a - rodless cavity; 4b - rod cavity; 8a - pilot valve of back pressure valve; 8b - main valve of back pressure valve; a - position where the displacement sensor sends a signal to the controller; b - position where the differential state switches to the non-differential state. Detailed implementation manners

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] It should be noted that in the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "top", "bottom", "one side", "the other side", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating that the device or component must have a specific orientation, be constructed and operated in a specific orientation.

[0029] See the attached Figures 1 to 9 , which gives the specific structure of an embodiment of a large-flow anti-cavitation hydraulic drive circuit with a differential function proposed by the present invention. The drive circuit includes an electro-hydraulic reversing valve 1, a shuttle valve 2, a displacement sensor 3, an oil cylinder 4, a simulated load 5, a differential valve 6, an oil tank 7, and a back-pressure valve 8.

[0030] The electro-hydraulic reversing valve 1, the rodless cavity 4a of the oil cylinder 4, the rod cavity 4b, and the differential valve 6 are connected in sequence; the displacement sensor 3 is arranged on one side of the oil cylinder 4; the simulated load 5 is connected to the outer end of the piston rod of the oil cylinder 4; the left oil port P1 of the shuttle valve 2 is communicated with the rodless cavity 4a of the oil cylinder 4, and the right oil port P2 of the shuttle valve 2 is communicated with the rod cavity 4b of the oil cylinder 4, that is, the pressure of the left oil port P1 of the shuttle valve 2 is the same as the pressure of the rodless cavity 4a, and the pressure of the right oil port P2 of the shuttle valve 2 is the same as the pressure of the rod cavity 4b; the electro-hydraulic reversing valve 1 is connected to the main oil circuit and the middle output oil port P3 of the shuttle valve 2; the oil tank 7 is connected to the electro-hydraulic reversing valve 1 through the back-pressure valve 8; the displacement sensor 3 can be used to monitor the position of the oil cylinder 4 in real time and send a signal to the controller to control the electromagnet of the back-pressure valve 8 to be energized when the oil cylinder 4 moves to the set position.

[0031] Among them, the electro-hydraulic reversing valve 1 is a pilot-operated control valve, its pilot stage is an electromagnetic reversing valve, the main valve stage is a hydraulic control reversing valve, the control method is internal control and external leakage type, and it has the characteristic of large flow capacity; the X port of the pilot valve 1a of the electro-hydraulic reversing valve is connected to the main oil circuit of the system and the middle output oil port P3 of the shuttle valve 2; the pilot control oil enters the control cavity of the main valve 1b of the electro-hydraulic reversing valve to make the electro-hydraulic reversing valve 1 act and realize the flow-through function.

[0032] The differential valve 6 is a two-position four-way electro-hydraulic reversing valve, the pilot control oil of which comes from the main oil circuit, and the pilot control oil circuit is connected to the main oil circuit and the second pipeline 10 through a three-way interface, and the other end of the second pipeline 10 is connected to the rod cavity 4b of the oil cylinder; the pilot control oil returns to the oil through the oil tank 7; when the pilot stage electromagnet is energized, under the pressure of the control oil, the spool of the differential valve 6 acts, and the oil returning from the rod cavity of the oil cylinder 4 is connected to the oil entering the rodless cavity 4a through the A→P flow path of the differential valve to realize the large-flow differential function and meet the working condition requirements of rapid forward feeding.

[0033] The back pressure valve 8 is a pilot-operated control valve placed in the return oil circuit. After the oil in the return oil circuit flows out from the T port of the main valve 1b of the electro-hydraulic directional valve, it enters the lower oil port (main valve of the back pressure valve) of the back pressure valve 8 through the internal flow passage of the valve block, and then enters the oil tank 7 from the side outlet of the back pressure valve 8. The outlet of the back pressure valve 8 is connected to the oil tank 7 through the third pipeline 11. The pilot stage of the back pressure valve 8 is an electromagnetic directional valve, and the main valve stage is a cartridge valve. After the pilot stage electromagnet is energized, the opening of the main valve stage decreases, the back pressure in the return oil circuit increases, and the oil cylinder 4 decelerates.

[0034] The displacement sensor 3 can monitor the position of the oil cylinder 4 in real time and send a signal to the controller, so as to control the electromagnet of the back pressure valve 8 to be energized when the oil cylinder 4 moves to the set position.

[0035] The shuttle valve 2 is a logic control valve. Its left oil port P1 is connected to the rodless cavity 4a of the oil cylinder 4, its right oil port P2 is connected to the rod cavity 4b of the oil cylinder 4, and its middle output oil port P3 is connected to the X port of the pilot valve 1a of the electro-hydraulic directional valve. The characteristic of the shuttle valve 2 that can perform pressure selection is used to ensure that the pressure at the X port of the pilot valve 1a of the electro-hydraulic directional valve is not zero under any circumstances, that is, it avoids the problem of accidental closing of the electro-hydraulic directional valve 1 caused by other unpredictable factors, and can play the role of "hydraulic insurance".

[0036] The oil tank 7 is an open-type oil tank. The two oil tanks 7 connected to the differential valve 6 and the back pressure valve 8 in the circuit refer to the same oil tank in the actual system, and play the roles of oil storage and heat dissipation in the system.

[0037] The rodless cavity 4a of the oil cylinder 4 is connected to the working oil port A of the main valve 1b of the electro-hydraulic directional valve through the first pipeline 9; the rod cavity 4b of the oil cylinder 4 is connected to the working oil port A of the differential valve 6 through the second pipeline 10. The P port of the differential valve 6 is connected to the rodless cavity 4a of the oil cylinder 4 through the internal flow passage of the valve block and via the first pipeline 9; the T port of the differential valve 6 is connected to the B port of the main valve 1b of the electro-hydraulic directional valve. In this embodiment, the first pipeline 9, the second pipeline 10 and the third pipeline 11 are all high-pressure resistant hoses.

[0038] The working principle of the present invention is as follows: As Figure 1As shown in the figure, the rodless cavity 4a of the working oil cylinder 4 is connected to the working oil port A of the main valve 1b of the electro-hydraulic directional valve through the first pipeline 9; the rod cavity 4b of the working oil cylinder 4 is connected to the working oil port A of the differential valve 6 through the second pipeline 10. The pilot stage of the electro-hydraulic directional valve 1 is an electromagnetic directional valve, and the main valve stage is a hydraulically controlled directional valve. The control mode is internal control and external leakage type. The pilot valve inlet X is connected to the internal main oil circuit, and the control oil enters the main valve control cavity to control the switching of the movement of the oil cylinder 4. The differential valve 6 is a two-position four-way electro-hydraulic directional valve, and the control oil of its pilot stage comes from the main oil circuit. When the solenoid of the pilot stage of the differential valve 6 is energized, under the pressure of the control oil, the spool of the differential valve 6 moves, and the oil returning from the rod cavity 4b is connected to the oil entering the rodless cavity 4a through the differential valve 6 to realize the differential function.

[0039] As Figure 4 shown, the simulation model is built according to the designed oil circuit of the back pressure valve 8 module. When the solenoid of the pilot stage of the back pressure valve is energized at t = 2s, the opening of the spool of the back pressure valve 8 decreases at this time, and the back pressure of the oil circuit increases, so that the expected back pressure effect can be achieved.

[0040] As Figure 5 shown, the overall oil circuit simulation model of the present invention is built. The reference numerals of the components in the model are the same as Figure 1 the reference numerals Figure 6 shown in the figure. The following is the simulation module of the logic control: The displacement sensor 3 collects the position of the oil cylinder 4 in real time and sends a signal to the controller. The controller compares this position signal with the pre-set position signal. When the actual position reaches the set switching position, the controller sends a signal to the solenoids of the pilot stages of the differential valve 6 and the back pressure valve 8, so that the differential valve 6 and the back pressure valve 8 are energized when the oil cylinder 4 moves to the expected position. Specifically, when the piston rod of the oil cylinder 4 moves to position a, the displacement sensor 3 sends a signal to the controller to control the solenoid of the pilot valve 8a of the back pressure valve to be energized. Then, the opening of the main valve 8b of the back pressure valve decreases, and the back pressure of the return oil increases, so that the piston rod of the oil cylinder 4 decelerates in advance to prevent the instantaneous speed of the piston rod from being too fast when the oil cylinder 4 moves to position b, resulting in the phenomenon of air suction in the main oil circuit; As Figure 7 shown in the figure, when the oil cylinder 4 travels to the moment of t = 0.52s and reaches position b, and the signal of the differential valve 6 switches from -40 to +40, the phenomenon of air suction appears in the ordinary oil circuit, while the main oil circuit pressure of the present invention will not show air suction, which verifies the feasibility of the solution of the present invention.

[0041] In practical applications, unpredictable situations may occur, such as the jamming of the spool of the backpressure valve and the slow response of electrical signals. These situations may cause the anti-air suction effect of the main oil circuit to be not obvious when switching from differential to non-differential state, resulting in slight air suction in the oil cylinder, reducing the pressure of the main oil circuit, and further causing the electro-hydraulic directional valve to close erroneously. Considering the consequences caused by the above unpredictable factors, the shuttle valve 2 is introduced to avoid the problem of the electro-hydraulic directional valve closing erroneously caused by unpredictable factors: Since the piston rod moves at a relatively high speed and the oil return flow is large, the pressure value in the rod chamber 4b will be relatively large under the action of the backpressure valve 8; the working logic of the shuttle valve 2 is to compare the pressures at both ends and output the higher pressure at the P3 oil port. Under the action of the shuttle valve 2, the pressure at the X port of the pilot valve 1a of the electro-hydraulic directional valve is the pressure in the rod chamber 4b at this time, rather than the very small pressure in the non-rod chamber 4a. Therefore, when switching from the differential action to the non-differential action, the electro-hydraulic directional valve 1 will not close erroneously. This situation has been verified through modeling and simulation in the Figure 9 curve.

[0042] In summary, a differential oil circuit designed by the present invention, by introducing the displacement sensor 3, the backpressure valve 8 and the shuttle valve 2, avoids the problem of air suction in the inlet oil circuit during the switching moment and the problem of the electro-hydraulic directional valve closing erroneously caused by slight air suction due to other unpredictable factors, reduces hydraulic shock, improves the stability and reliability of the operation process of the oil cylinder 4, and at the same time is of great significance for extending the service life of hydraulic components to a certain extent.

[0043] Matters not detailed in the present invention are all well-known technologies.

[0044] The embodiments described above are only used to describe the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A large-flow anti-voiding hydraulic drive circuit with differential function, characterized in that: The circuit includes an electro-hydraulic directional valve, a shuttle valve, a displacement sensor, an oil cylinder, a simulated load, a differential valve, an oil tank, and a backpressure valve; the electro-hydraulic directional valve, the oil cylinder, and the differential valve are connected in sequence; the displacement sensor is arranged on one side of the oil cylinder; the simulated load is connected to the outer end of the piston rod of the oil cylinder; the left oil port of the shuttle valve is communicated with the rodless cavity of the oil cylinder, and the right oil port is communicated with the rod chamber of the oil cylinder; the electro-hydraulic directional valve is connected to the main oil circuit and the middle oil port of the shuttle valve; the oil tank is connected to the electro-hydraulic directional valve through the backpressure valve; The electro-hydraulic directional valve is a pilot-operated control valve, its pilot stage is an electromagnetic directional valve, the main valve stage is a hydraulically controlled directional valve, and the control mode is internal control and external leakage; the X port of the pilot valve of the electro-hydraulic directional valve is connected to the main oil circuit and the middle oil port of the shuttle valve; the pilot control oil enters the control cavity of the main valve of the electro-hydraulic directional valve, causing the electro-hydraulic directional valve to act and realizing the flow-through function; The differential valve is a two-position four-way electro-hydraulic directional valve, and the control oil of its pilot stage comes from the main oil circuit. The pilot control oil circuit is connected to the main oil circuit and the rod chamber of the oil cylinder through a three-way interface, and the rod chamber of the oil cylinder is connected to the three-way interface through a second pipeline; the pilot control oil returns to the oil tank; when the pilot-stage electromagnet is energized, under the pressure of the control oil, the differential valve spool acts, and the oil returning from the rod chamber passes through the A→P flow path of the differential valve and is connected to the oil entering the rodless cavity, realizing the large-flow differential function and meeting the working condition requirements of rapid forward feeding; The backpressure valve is a pilot-operated control valve placed in the return oil circuit. After the oil in the return oil circuit flows out from the T port of the electro-hydraulic directional valve, it enters the lower oil port of the backpressure valve through the internal flow path of the valve block, and then enters the oil tank from the outlet beside the backpressure valve. The outlet of the backpressure valve is connected to the oil tank through a third pipeline; the pilot stage of the backpressure valve is an electromagnetic directional valve, and the main valve stage is a cartridge valve. After the pilot-stage electromagnet is energized, the opening of the main valve stage decreases, the backpressure of the return oil circuit increases, and the oil cylinder decelerates.

2. The large-flow anti-cavitation hydraulic drive circuit with differential function according to claim 1, characterized in that: The displacement sensor monitors the position of the oil cylinder in real time and sends a signal to the controller to control the electromagnet of the backpressure valve to be energized when the oil cylinder moves to the set position.

3. A large-flow anti-voiding hydraulic drive circuit with differential function according to claim 1, characterized in that: The shuttle valve is a logic control valve, its left oil port is communicated with the rodless cavity of the oil cylinder, the right oil port is communicated with the rod chamber of the oil cylinder, and the middle oil port is communicated with the X port of the pilot stage of the electro-hydraulic directional valve.

4. The large-flow anti-voiding hydraulic drive circuit with differential function according to claim 3, characterized in that: The oil tank is an open-type oil tank, which plays the role of storing oil and dissipating heat in the system.

5. A large-flow anti-voiding hydraulic drive circuit with differential function according to claim 3, characterized in that: The rodless cavity of the oil cylinder is communicated with the working oil port A of the hydraulically controlled directional valve; the rod chamber of the oil cylinder is communicated with the working oil port A of the differential valve; the P port of the differential valve is connected to the rodless cavity of the oil cylinder through the internal flow path of the valve block via a first pipeline; the T port of the differential valve is connected to the B port of the hydraulically controlled directional valve.

6. A large-flow anti-voiding hydraulic drive circuit with a differential function according to claim 5, characterized in that: The first pipeline, the second pipeline, and the third pipeline are all high-pressure-resistant hoses.

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