WO2012062167A1

WO2012062167A1 - Hydraulic system

Info

Publication number: WO2012062167A1
Application number: PCT/CN2011/081421
Authority: WO
Inventors: 杨琴; 谭碧峰; 韩术亭
Original assignee: 北汽福田汽车股份有限公司; 北京智科投资管理有限公司
Priority date: 2010-11-12
Filing date: 2011-10-27
Publication date: 2012-05-18
Also published as: CN102465934A; RU2538351C2; BR112013011337A2; CN102465934B; RU2013112809A

Abstract

A hydraulic system with a high-pressure pumping state and a low-pressure pumping state. The hydraulic system comprises: a first hydraulic cylinder (210) and a second hydraulic cylinder (220), the first hydraulic cylinder (210) and the second hydraulic cylinder (220) being both provided with a non-rod chamber (211, 221) and a rod end chamber (212, 222); a switch valve; and a first channel placed between the non-rod chamber (211) of the first hydraulic cylinder and the non-rod chamber (221) of the second hydraulic cylinder. The switch valve controls the connection/disconnection of the first channel. The hydraulic system further comprises a second channel in parallel connection with the first channel and placed between the non-rod chamber (211) of the first hydraulic cylinder and the non-rod chamber (221) of the second hydraulic cylinder, wherein the switch valve controls the second channel to connect during the low-pressure pumping state and disconnect during the high-pressure pumping state. In the case of low-pressure pumping, the non-rod chambers of two hydraulic cylinders can be in communication with each other through either the first channel or the second channel. Thus the flow capability between the non-rod chambers of the two hydraulic cylinders is improved and pipe explosion is prevented, thereby ensuring the reliable cutoff or communication between the non-rod chambers of the two hydraulic cylinders in the case of high-pressure pumping, reduce system impact, and increase system reliability.

Description

Hydraulic system

Technical field

This invention relates to a hydraulic system, and more particularly to a hydraulic system that requires switching between high and low pressure pumping conditions. Background technique

In the field of construction machinery, such as concrete pump trucks, tow pumps, on-board pumps, etc., high and low pressure pumping state switching is one of the most important modes of operation for these mechanical hydraulic systems.

Taking a concrete pump as an example, FIG. 1 illustrates the construction of such a prior art hydraulic system, which includes: a fuel tank (not shown); two hydraulic cylinders 1, 2, the hydraulic cylinder 1 has a rodless chamber 3 and a There is a rod chamber 4, the hydraulic cylinder 2 has a rodless chamber 5 and a rod chamber 6; - a high and low pressure switching valve 7, including an electromagnetic reversing valve 8; - a main reversing valve (shown in the figure), setting Between the high and low pressure switching valve 7 and the oil tank; the two rodless oil tubes 9, 10 are respectively connected between the rodless chambers 3, 5 of the two hydraulic cylinders and the high and low pressure switching valves 7; the two rod chamber oil tubes 11, 12 , respectively connected between the rod chambers 4, 6 and the high and low pressure switching valves 7 of the two hydraulic cylinders; the two inlet and outlet oil pipes 13, 14 are connected between the main reversing valve and the high and low pressure switching valves 7.

When the low pressure pumping, the high pressure oil enters the rod chamber 6 of the hydraulic cylinder 2 from the inlet and outlet oil pipe 13 through the high and low pressure switching valve 7, and the rod chamber oil pipe 12, and pushes the piston of the hydraulic cylinder 2 to move in the direction of the rodless cavity thereof, thereby causing The high-pressure oil in the rodless chamber 5 of the hydraulic cylinder 2 enters the rodless chamber 3 of the hydraulic cylinder 1 through the rodless chamber oil pipe 10, the high and low pressure switching valve 7 and the rodless chamber oil pipe 9, and pushes the piston of the hydraulic cylinder 1 to The movement of the rod cavity causes the high pressure oil in the rod chamber 4 of the hydraulic cylinder 1 to pass through the rod chamber oil pipe 11, the high and low pressure switching valve 7, and the inlet and outlet oil pipe 14 to the oil tank. When the hydraulic cylinder reaches the end of the stroke, the proximity switch is activated. At this time, the system is reversed under the control of the main reversing valve. The high pressure oil passes from the inlet and outlet oil pipe 14 through the high and low pressure switching valve 7, and the rod chamber oil pipe 11 enters the hydraulic cylinder 1. Rod cavity 4, and pushes the hydraulic cylinder 1 The piston moves toward the rodless cavity thereof, so that the high pressure oil in the rodless chamber 3 of the hydraulic cylinder 1 enters the rodless chamber 5 of the hydraulic cylinder 2 through the rodless chamber oil pipe 9, the high and low pressure switching valve 7 and the rodless cavity oil pipe 10. And pushing the piston of the hydraulic cylinder 2 to move in the rod cavity direction, so that the high pressure oil in the rod chamber 6 of the hydraulic cylinder 2 passes through the rod chamber oil pipe 12, the high and low pressure switching valve 7 and the inlet and outlet oil pipe 13 to return to the oil tank. So, complete a trip.

In the prior art hydraulic system, during low pressure pumping, two 32-diameter hoses are commonly used between the rodless chambers of the two hydraulic cylinders, namely the two rodless chamber tubes 9, 10 in FIG. Since the hydraulic cylinder has an area ratio of the rod cavity and the rodless cavity, the flow rate of the rodless cavity is low when pumping at low pressure, and the frequent commutation of the system causes the system to have a large impact, and the rodless tube 9 and 10 are extremely easy. Explosion, and system noise, heat, etc., which in turn invalidate the system.

In view of the above drawbacks of the hydraulic system, it is necessary to improve it to solve the problems of the existing hydraulic system and improve the reliability of the system. Summary of the invention

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a hydraulic system that, when applied to an engineering machine, increases the flow capacity between the rodless chambers of the two hydraulic cylinders to avoid bursting.

In order to achieve the above object, the present invention adopts the following technical solutions:

A hydraulic system having two states of high pressure pumping and low pressure pumping, the hydraulic system comprising: a first hydraulic cylinder and a second hydraulic cylinder, the first hydraulic cylinder and the second hydraulic cylinder Each having a rodless chamber and a rod chamber; a switching valve; a first passage disposed between the rodless chamber of the first hydraulic cylinder and the rodless chamber of the second hydraulic cylinder, the switching valve controlling the And an opening and closing of the first passage; and a second passage disposed in parallel with the first passage between the rodless cavity of the first hydraulic cylinder and the rodless cavity of the second hydraulic cylinder; wherein the switching The valve controls the second passage to conduct during the low pressure pumping state and to shut off during the high pressure pumping state.

Further, the switching valve controls the on and off of the second passage through a logic valve disposed on the second passage. Further, the hydraulic system further includes a valve block, the valve group includes an oil passage block, and the oil passage block is provided with a rodless chamber of the first hydraulic cylinder and a rodless rod of the second hydraulic cylinder a first main oil passage communicating with the chamber, the second passage including the first main oil passage, the switching valve controlling the first main oil passage to be turned on in a low pressure pumping state and in a high pressure pumping state Cut off.

Further, a logic valve is disposed on the first main oil passage of the oil block of the valve block, and the switching valve controls the opening and closing of the first main oil passage by controlling the logic valve.

Further, a jack is further disposed on the oil block of the valve block, and the logic valve is inserted in the jack.

Further, a first branch oil passage and a second branch oil passage are further disposed in the oil passage block of the valve block, and the first passage includes the first branch oil passage, the second branch oil passage, and the a third branch oil passage outside the valve block.

Further, the switching valve is a high and low pressure switching valve, the high and low pressure switching valve is provided with an interface, a logic valve and a reversing valve, the logic valve is disposed between the interfaces, the reversing valve and the The control port of the logic valve is connected.

Further, the interface of the high and low pressure switching valve comprises: a first rodless cavity oil pipe port, a second rodless cavity oil pipe port, a first rod cavity oil pipe port, a second rod cavity oil pipe port, a first inlet and outlet The oil port and the second inlet and outlet ports.

Further, the logic valve includes: a first logic valve installed between the first rodless cavity oil pipe port of the high and low pressure switching valve and the first inlet and outlet port; a second logic valve installed in the a second rod chamber oil pipe port and a first inlet and outlet port of the high and low pressure switching valve; a third logic valve installed in the first rod cavity oil pipe port and the second inlet and outlet port of the high and low pressure switching valve a fourth logic valve disposed between the second rodless chamber oil pipe port and the second inlet and outlet port of the high and low pressure switching valve; a fifth logic valve installed at the first of the high and low pressure switching valves Between the rod chamber oil port and the second rod chamber port; and a sixth logic valve disposed between the first rodless chamber port and the second rodless tube port of the high and low pressure switching valve.

Further, a control port of the first logic valve, the fourth logic valve, and the fifth logic valve The first working port of the reversing valve is in communication, and the control ports of the second logic valve, the third logic valve and the sixth logic valve are in communication with the second working port of the reversing valve.

Further, the second working port of the reversing valve is further in communication with a control port of the logic valve disposed on the second passage.

Further, between the first rodless cavity oil pipe port of the high and low pressure switching valve and the rodless cavity of the first hydraulic cylinder, the first rod cavity oil pipe port of the high and low pressure switching valve Between the rod chambers of the first hydraulic cylinder, between the second rodless chamber oil port of the high and low pressure switching valve and the rodless chamber of the second hydraulic cylinder, and the high and low pressure switching valve A communication line is disposed between the second rod chamber oil pipe port and the rod chamber of the second hydraulic cylinder.

As described above, the hydraulic system of the present invention provides a parallel first passage and a second passage between the rodless chambers of the two hydraulic cylinders. When the low pressure pumping, the oil in the rodless chamber of the two hydraulic cylinders can be Through the first channel communication, it can also communicate through the second channel, thus increasing the flow capacity between the rodless chambers of the two hydraulic cylinders, avoiding the squib, thereby ensuring that the two hydraulic cylinders have no rod during high and low pressure pumping. The cavity is reliably closed or connected, and the system impact is reduced, which improves the reliability of the system. DRAWINGS

The technical solutions of the present invention and its advantages will be apparent from the following description of the preferred embodiments of the invention.

1 is a schematic view showing the configuration of a hydraulic system of a concrete pump of the prior art;

2 is a schematic structural view of a hydraulic system of the present invention;

3 is a schematic structural view of a valve block of a hydraulic system according to the present invention;

Figure 4 is a cross-sectional view of the logic valve portion of the valve block of the hydraulic system of the present invention;

Figure 5 is a schematic plan view showing the structure of the valve block of the hydraulic system of the present invention;

Figure 6 is a schematic view of the oil circuit of the hydraulic system of the present invention at low pressure pumping;

Figure 7 is a schematic view of the oil circuit of the hydraulic system of the present invention when pumped at high pressure. detailed description

Hereinafter, the present invention will be specifically described by way of exemplary embodiments. However, it is to be understood that the elements, structures, and features described in one embodiment may be beneficially incorporated in other embodiments without further recitation.

The hydraulic system of the present invention can be applied to construction machinery equipment such as concrete pump trucks, tow pumps, vehicle pumps, and the like.

2 illustrates the structure of a hydraulic system 1000 according to a preferred embodiment of the present invention. The hydraulic system 1000 includes: a valve block 100, a first hydraulic cylinder 210 and a second hydraulic cylinder 220, a high and low pressure switching valve 230, and a plurality of oil pipes. Also included is a fuel tank and a main reversing valve (not shown) located between the fuel tank and the high and low pressure switching valve 230.

The structure of the valve block 100 is illustrated in Figures 3 through 5, which includes an oil block 20 and a logic valve 40.

Referring to FIG. 3, the oil block 20 is provided with: a first main oil passage 21, the two ends of which are respectively opened to the first hydraulic cylinder connection port 22 and the second hydraulic cylinder connection port 23; the first branch oil passage 24, two of The ends are respectively open to the first rodless cavity oil pipe connection port 25 and the first hydraulic cylinder connection port 22; the second branch oil passage 26 has two ends respectively open to the second rodless cavity oil pipe connection port 27 and the second hydraulic cylinder connection a port 23; a control oil passage (not shown) having one end open to the control port 29; and a socket 30 located on the first main oil passage 21 and communicating therewith;

Referring to FIG. 4, the logic valve 40 includes: a logic valve insert 41 inserted into the insertion hole 30 and disposed on the first main oil passage 21. Referring to FIG. 4, the logic valve insert 41 includes a spool 42, a valve sleeve 43, a spring 44, and a baffle 45. Wherein, the valve core 42 can move within the valve sleeve 43, the logic valve insert 41 is opened or closed, the opening pressure is determined by the spring 44, the baffle 45 is a fixed sealing assembly, and the control cover 50 is fixed to the oil. Above the jack 30 of the block 20, the control oil passage 51 is disposed in the control cover 50, and one end portion 52 thereof communicates with the control oil passage of the oil passage block 20, and the other end portion 53 is connected to the logic valve insert 41. The on and off of the liquid flow in the first main oil passage 21 is controlled by the control oil in the control oil passage 51. Referring to FIG. 3, preferably, the oil block 20 has a top surface 31, a bottom surface 32 and a side surface 33, and the control cover 50 is mounted on the top surface 31, the first hydraulic cylinder connection port 22 The second hydraulic cylinder connection port 23 is disposed on the bottom surface 32, and the first rodless cavity oil pipe connection port 25 and the second rodless cavity oil pipe connection port 27 are disposed on the side surface 33.

Referring to FIG. 5, preferably, the oil block 20 of the valve block 100 is additionally provided with eight fixing holes 60. When the valve block 100 is connected to the hydraulic system, eight M16 bolts pass through the eight fixed holes. The bore 60 secures the valve block 100 to the two hydraulic cylinders.

In addition, the first branch oil passage 24 of the valve block 100 may not share a first hydraulic cylinder connection port 22 with the first main oil passage 21, but a third hydraulic cylinder connection port; a second branch oil passage 26, It is also possible not to share a second hydraulic cylinder connection port 23 with the first main oil passage 21, but to provide a fourth hydraulic cylinder connection port.

When the valve block 100 is in operation, the control oil can enter the control oil passage of the oil passage block from the control oil port 29, and exerts a force on the logic valve insert 41 via the control oil passage 51 in the control cover 50 to make the first main The oil passage 21 is interrupted; when the control oil is shut off, the control oil force applied to the logic valve insert 41 is removed, and when the high pressure oil passes through the first main oil passage 21, the spring force of the upper portion of the spool of the logic valve insert 41 can be overcome. The spool 42 is opened to communicate with the first main oil passage 21.

Referring to FIG. 2, the first hydraulic cylinder 210 has a rodless chamber 211 and a rod chamber 212 having a rodless chamber 221 and a rod chamber 222.

The high and low pressure switching valve 230 is provided with six oil pipe ports, which are a first rodless cavity oil pipe port 231, a second rodless cavity oil pipe port 232, a first rod cavity oil pipe port 233, and a second rod cavity oil pipe. Port 234, first inlet and outlet port 235 and second inlet and outlet port 236.

The high and low pressure switching valve 230 is further provided with six logic valves, which are respectively: a first logic valve 241 installed between the first rodless cavity oil pipe port 231 and the first inlet and outlet port 235; The second logic valve 243 is disposed between the first rod chamber oil pipe port 233 and the second inlet and outlet port 236; The fourth logic valve 244 is disposed between the second rodless cavity oil pipe port 232 and the second inlet and outlet port 236; a valve 245 is disposed between the first rod cavity oil pipe port 233 and the second rod cavity oil pipe port 234; and a sixth logic valve 246 is disposed on the first rodless cavity oil pipe port 231 and the second rodless cavity Between the oil pipe ports 232.

Further, the high and low pressure switching valve 230 is also provided with an electromagnetic reversing valve 250.

The hydraulic system 1000 is provided with a plurality of oil pipes, which include: a rodless cavity oil pipe 261, a first rodless cavity oil pipe port 231 connected to the high and low pressure switching valve 230, and a first rodless cavity oil pipe connection port 25 of the valve block 100. The rodless cavity oil pipe 262 is connected between the second rodless cavity oil pipe port 232 of the high and low pressure switching valve 230 and the second rodless cavity oil pipe connection port 27 of the valve block 100; and the rod cavity oil pipe 263 is connected to the high The first rod chamber oil pipe port 233 of the low pressure switching valve 230 and the rod chamber 212 of the first hydraulic cylinder 210; a rod cavity oil pipe 264 connected to the second rod cavity oil pipe port 234 of the high and low pressure switching valve 230 The second hydraulic cylinder 220 has between the rod chambers 222; the inlet and outlet oil pipes 265 are connected between the first inlet and outlet ports 235 of the high and low pressure switching valves 230 and the oil tank; the inlet and outlet oil pipes 266 are connected to the second high and low pressure switching valves 230. Between the inlet and outlet ports 236 and the fuel tank; and a control oil pipe 270 connected between the control port 29 of the valve block 100 and the high and low pressure switching valve 230.

Figures 6 and 7 respectively illustrate the oil circuit of the hydraulic system 1000 for controlling the oil and its main line in the low pressure pumping and high pressure pumping states.

The dotted line in Fig. 6 shows the oil path of the control oil during low pressure pumping. As shown in the figure, the electromagnetic reversing valve 250 of the high and low pressure switching valve 230 is de-energized, and the control oils 311, 312 act on the logic valve 241 via the shuttle valve. The control ports of 244, 245, the control oil of the control ports of the logic valves 242, 243, 246, and 40 are returned to the oil through the T port of the electromagnetic reversing valve 250.

The solid line in Figure 6 shows the oil path from the main oil circuit during low pressure pumping. As shown, the high pressure oil enters the high and low pressure switching valve 230 from the second inlet and outlet port 236 and overcomes the third logic valve 243 spool. The upper spring force pushes the valve core open, so that the second inlet and outlet port 236 communicates with the first rod chamber oil pipe port 233, and the high pressure oil enters the rod cavity 212 of the first hydraulic cylinder 210 via the rod cavity oil pipe 263, and pushes The piston of the hydraulic cylinder moves, so that the oil in the rodless chamber 211 of the first hydraulic cylinder 210 enters the valve block 100 through the first hydraulic cylinder connection port 22. At this time, the high pressure oil is divided into two paths, one way to overcome the valve group 100. The spring force of the upper part of the valve valve 40 of the built-in logic valve 40 pushes the valve core open, passes through the first main oil passage 21 and then enters the rodless chamber 221 of the second hydraulic cylinder 220 through the second hydraulic cylinder connection port 23, and the other passage valve The first branch oil passage 24 in the group 100, the first rodless chamber oil pipe connection port 25, and the rodless cavity oil pipe 261 enter the high and low pressure switching valve 230 through the first rodless cavity oil pipe port 231, and overcome the sixth logic valve 246 valve. The spring force of the upper part of the core pushes the valve core through the second rodless cavity oil pipe port 232, the rodless cavity oil pipe 262, the second rodless cavity oil pipe connection port 27 of the valve block 100, the second branch oil passage 26 and The second hydraulic cylinder connection port 23 enters the rodless chamber 221 of the second hydraulic cylinder 220, and the high pressure oil entering the rodless chamber 221 of the second hydraulic cylinder 220 pushes the piston of the hydraulic cylinder to move, so that the second hydraulic cylinder 220 has the rod The oil in the cavity 222 passes through the rod cavity oil pipe 264 and enters the high and low pressure switching valve 230 through the second rod cavity oil pipe port 234, and then the valve core is opened by overcoming the spring force on the second logic valve 242 spool. The second rod-shaped oil pipe port 234 communicates with the first inlet and outlet port 235, and the hydraulic oil returns to the oil through the first inlet and outlet port 235. . When the hydraulic cylinder reaches the end of the stroke, the proximity switch is activated. At this time, the system is reversed under the control of the main reversing valve, and the high pressure oil enters the oil passage from the first inlet and outlet port 235, and returns to the fuel tank from the second inlet and outlet port 236. The oil circuit is just the opposite and will not be repeated here.

The dotted line in Fig. 7 illustrates the oil path of the control oil during high pressure pumping. As shown, the electromagnetic reversing valve 250 of the high and low pressure switching valve 230 is energized, and the control oils 311, 312 act on the logic valves 242, 243 via the shuttle valve. At the control ports of 246 and 40, the control oil of the control ports of the logic valves 241, 244, and 245 is returned to the oil through the T port of the electromagnetic reversing valve 250.

The solid line in Figure 7 shows the oil path from the main oil circuit during high pressure pumping. As shown, the high pressure oil enters the high and low pressure switching valve 230 from the second inlet and outlet port 236 and overcomes the fourth logic valve 244 spool. The upper spring force pushes the valve core apart, so that the second inlet and outlet port 236 communicates with the second rodless chamber oil pipe port 232, and the high pressure oil passes through the rodless cavity oil pipe 262 and the second rodless cavity oil pipe connection port of the valve block 100. 27. The second branch oil passage 26 and the second hydraulic cylinder connection port 23 enter the rodless chamber 221 of the second hydraulic cylinder 220, and push the piston of the hydraulic cylinder to move, so that the second hydraulic cylinder 220 has the rod chamber 222. The oil passes through the rod cavity oil pipe 264 and enters the high and low pressure switching valve 230 through the second rod cavity oil pipe port 234, and then overcomes the spring force of the upper portion of the fifth logic valve 245 valve spool to open the valve core, so that the second Have The rod cavity oil pipe port 234 communicates with the first rod cavity oil pipe port 233, enters the rod cavity oil pipe 263 through the first rod cavity oil pipe port 233, and then enters the rod cavity 212 of the first hydraulic cylinder 210, and pushes the hydraulic cylinder The piston moves, so that the oil in the rodless chamber 211 of the first hydraulic cylinder 210 passes through the first hydraulic cylinder connection port 22 of the valve block 100, the first branch oil passage 24, the first rodless chamber oil pipe connection port 25, and After the rod chamber oil pipe 261 enters the high and low pressure switching valve 230 through the first rodless chamber oil pipe port 231, and then over the valve body of the upper portion of the first logic valve 241 spool to open the valve core, so that the first rodless cavity oil pipe The port 231 communicates with the first inlet and outlet port 235 and returns to the oil tank through the first inlet and outlet port 235. When the hydraulic cylinder reaches the end of the stroke, the proximity switch is activated. At this time, the system is reversed under the control of the main reversing valve. The high pressure oil enters the oil passage from the first inlet and outlet port 235, and returns to the fuel tank from the second inlet and outlet port 236. The road is just the opposite, so I won't go into details here.

As described above, the hydraulic system of the present invention provides a parallel first passage and a second passage between the rodless chambers of the two hydraulic cylinders. When the low pressure pumping, the oil in the rodless chamber of the two hydraulic cylinders can be Through the first channel communication, it can also communicate through the second channel, thereby increasing the flow capacity between the rodless chambers of the two hydraulic cylinders and avoiding the squib; preferably, the hydraulic system of the present invention utilizes two rodless chambers The passage formed by the oil pipe and the high and low pressure switching valve is used as the first passage. On the basis of this, a valve block is further disposed between the rodless chambers of the two hydraulic cylinders, and the first main oil passage provided in the valve group is used as the two hydraulic cylinders. The second passage of oil communication in the rodless chamber, when the low pressure pumping, the oil in the rodless chamber of the two hydraulic cylinders can pass through the first passage formed by the two rodless chamber oil pipes and the high and low pressure switching valves Communication can also be communicated through the second passage formed by the first main oil passage of the valve block, thereby increasing the flow capacity between the rodless chambers of the two hydraulic cylinders, avoiding the bursting of the tube, thereby ensuring the high and low pressure pumps Reliable two-cylinder cylinder without rod cavity Closed or connected, and reduces system shocks, improving system reliability.

Claims

Rights request

A hydraulic system, the hydraulic system having two states of high pressure pumping and low pressure pumping, the hydraulic system comprising:

a first hydraulic cylinder and a second hydraulic cylinder, the first hydraulic cylinder and the second hydraulic cylinder each having a rodless cavity and a rod cavity;

Switching valve

a first passage, disposed between the rodless cavity of the first hydraulic cylinder and the rodless cavity of the second hydraulic cylinder, wherein the switching valve controls on and off of the first passage; The hydraulic system also includes:

a second passage, disposed in parallel with the first passage between the rodless cavity of the first hydraulic cylinder and the rodless cavity of the second hydraulic cylinder;

Wherein the switching valve controls the second passage to be turned on when in the low pressure pumping state and to be cut off in the high pressure pumping state.

2. The hydraulic system according to claim 1, wherein the switching valve controls the opening and closing of the second passage through a logic valve disposed on the second passage.

3. The hydraulic system according to claim 1, wherein the hydraulic system further comprises a valve block, the valve group includes an oil passage block, and the oil passage block is provided with the first hydraulic cylinder a first main oil passage in which the rodless chamber communicates with the rodless chamber of the second hydraulic cylinder, the second passage includes the first main oil passage, and the switching valve controls the first main oil passage at a low pressure It is turned on in the pumping state and cut off in the high pressure pumping state.

4. The hydraulic system according to claim 3, wherein a logic valve is disposed on a first main oil passage of the oil block of the valve block, and the switching valve controls the logic valve by controlling the logic valve The on/off of the first main oil passage is described.

The hydraulic system according to claim 4, wherein the oil block of the valve block is further provided with a socket, and the logic valve is inserted into the socket.

The hydraulic system according to claim 3, wherein the oil passage block of the valve block is further provided with a first branch oil passage and a second branch oil passage, and the first passage includes the first a branch oil passage, the second branch oil passage, and a third branch oil passage located outside the valve block.

The hydraulic system according to any one of claims 1 to 6, wherein the switching valve is a high and low pressure switching valve, and the high and low pressure switching valve is provided with an interface, a logic valve, and a reversing valve. The logic valve is disposed between the interfaces, and the reversing valve is coupled to the control port of the logic valve.

8. The hydraulic system according to claim 7, wherein the interface of the high and low pressure switching valve comprises: a first rodless cavity oil pipe port, a second rodless cavity oil pipe port, and a first rod cavity oil pipe The mouth, the second rod chamber oil pipe port, the first inlet and outlet ports and the second inlet and outlet ports.

9. The hydraulic system according to claim 8, wherein the logic valve comprises: a first logic valve, a first rodless chamber oil pipe port and a first inlet and outlet port installed in the high and low pressure switching valve Between

a second logic valve is disposed between the second rod chamber oil pipe port of the high and low pressure switching valve and the first inlet and outlet port;

a third logic valve is disposed between the first rod chamber oil pipe port and the second inlet and outlet port of the high and low pressure switching valve;

a fourth logic valve, the second rodless cavity oil pipe port and the second inlet installed in the high and low pressure switching valve Between the oil outlets;

a fifth logic valve is disposed between the first rod chamber oil pipe port of the high and low pressure switching valve and the second rod cavity oil pipe port;

And a sixth logic valve disposed between the first rodless chamber oil pipe port of the high and low pressure switching valve and the second rodless cavity oil pipe port.

10. The hydraulic system according to claim 9, wherein the control ports of the first logic valve, the fourth logic valve, and the fifth logic valve are in communication with the first working oil port of the reversing valve. The control ports of the second logic valve, the third logic valve and the sixth logic valve are in communication with the second working oil port of the reversing valve.

11. The hydraulic system according to claim 9, wherein the second working port of the reversing valve is further in communication with a control port of the logic valve disposed on the second passage.

The hydraulic system according to claim 8, wherein the first rodless chamber oil pipe port of the high and low pressure switching valve and the rodless cavity of the first hydraulic cylinder, the high and low pressure Between the first rod chamber oil pipe port of the switching valve and the rod chamber of the first hydraulic cylinder, the second rodless chamber oil pipe port of the high and low pressure switching valve, and the second hydraulic cylinder A communication line is disposed between the rodless chambers and between the second rod chamber tubing port of the high and low pressure switching valve and the rod chamber of the second hydraulic cylinder.