An automatically reversing two-position eight-way reversing valve and its usage method

Abstract

The present invention discloses an automatic reversing two-position eight-way reversing valve and its usage method, belonging to the technical field of reversing valves. The reversing valve includes a valve body and a main spool, and also includes a floating piston, a spring and a limiting piston. The valve body is provided with a valve cavity, a left valve cover and a right valve cover. The main spool is provided with a spool hole. The floating piston and the limiting piston are respectively sealed at the left end and the right end of the spool hole. The floating piston and the limiting piston are respectively slidably connected to the main spool. The spool hole includes a left core hole for accommodating the floating piston and a right core hole for accommodating the spring and the limiting piston. The left core hole is communicated with the right core hole through a through hole. The aperture of the left core hole is smaller than that of the right core hole. The present invention can achieve automatic reversing. During the reversing process, the hydraulic impact of the medium on the valve body and the main spool is reduced, the reversing is smooth without impact, and the stability of the reversing valve is greatly improved.

Description

Technical Field

[0001] The present invention relates to an automatically reversing two-position eight-way reversing valve and its usage method, belonging to the technical field of reversing valves. Background Art

[0002] Existing reversing valves generally control the reversal of the reversing valve by applying or not applying pneumatic or hydraulic pressure. Usually, it is necessary to manually control the opening and closing of the pressure to achieve the purpose of controlling the reversal of the reversing valve. Once the controlled pressure switch is turned on, a large hydraulic shock will be generated during the reversal. In working conditions that require frequent reversals, it is beneficial to reduce the instantaneous shock to improve the service life of the control valve and the controlled equipment.

[0003] In addition, manual control also requires external oil pipes and control switches, which increases the usage cost and the external oil circuit will increase the risk of hydraulic oil leakage in the hydraulic system. The leakage of hydraulic oil may cause environmental pollution. Summary of the Invention

[0004] In view of the deficiencies of the existing technology, the present invention provides an automatically reversing two-position eight-way reversing valve and its usage method.

[0005] The technical solution for the present invention to solve the above technical problems is as follows: An automatically reversing two-position eight-way reversing valve includes a valve body and a main spool disposed in the valve body, and further includes a floating piston, a spring and a limit piston disposed in the main spool. The valve body is provided with a valve cavity for the main spool to move, a left valve cover and a right valve cover for limiting the movement amount of the main spool. The main spool is provided with a spool hole. The floating piston and the limit piston are respectively sealed at the left end and the right end of the spool hole. The floating piston and the limit piston are respectively slidably connected to the main spool. The spool hole includes a left core hole for accommodating the floating piston and a right core hole for accommodating the spring and the limit piston. The left core hole is communicated with the right core hole through a through hole. The aperture of the left core hole is smaller than that of the right core hole;

[0006] The valve body is further provided with a P1 oil port, a P2 oil port, an A oil port, a B oil port, a T1 oil port, a T2 oil port, a Pi1 oil port and a Pi2 oil port. The Pi1 oil port is disposed in the middle of the valve cavity and communicated with the right core hole. The Pi2 oil port is disposed at the left end of the valve cavity;

[0007] When the hydraulic oil force of the Pi2 oil port on the main spool is less than the sum of the hydraulic oil force of the Pi1 oil port on the main spool and the spring force of the spring, the main spool is in the left position, the A oil port is communicated with the T1 oil port, and the B oil port is communicated with the T2 oil port; when the hydraulic oil force of the Pi2 oil port on the main spool is greater than the sum of the hydraulic oil force of the Pi1 oil port on the main spool and the spring force of the spring, the main spool is in the right position, the PI oil port is communicated with the A oil port, and the P2 oil port is communicated with the B oil port.

[0008] The beneficial effects of the present invention are as follows: when the main spool is in the right position, the PI oil port is communicated with the A oil port, and the P2 oil port is communicated with the B oil port. When reversing is required, only the hydraulic pressure of the Pi1 oil port needs to be increased. The diameter of the left core hole on the floating piston side is small, and the diameter of the right core hole on the limit piston side is large. The left core hole on the floating piston side is communicated with the right core hole on the limit piston side, and the hydraulic oil pressures on both sides are the same. The side with a large hydraulic oil acting area has a large hydraulic oil force on the main spool, that is, a large hydraulic pressure. Therefore, the main spool is subjected to a hydraulic pressure towards the floating piston side. When the sum of this hydraulic pressure and the spring force is greater than the hydraulic oil force of the Pi2 oil port on the spool, the main spool in the right position actively moves to the left position to realize the automatic reversing of the main spool. There is no need for manual control, and there is no need to set up a manual control switch and an external oil circuit structure, reducing the risk of oil leakage. The main spool of the present invention can realize automatic reversing, and the reversing process can reduce the hydraulic impact of the medium on the valve body and the main spool. The reversing is stable and without impact, greatly improving the stability of the reversing valve.

[0009] On the basis of the above technical solution, the present invention can be further improved as follows.

[0010] Further, a first communication passage for communicating the A oil port with the T1 oil port when the main spool is in the left position is provided on the main spool, and the first communication passage is used for communicating the P1 oil port with the A oil port when the main spool is in the right position.

[0011] The beneficial effect of adopting the above further solution is that it not only meets the requirement that the A oil port can be communicated with the T1 oil port through the first communication passage when the main spool is in the left position, but also meets the requirement that the P1 oil port can be communicated with the A oil port through the first communication passage when the main spool is in the right position.

[0012] Further, the first communication passage includes a first annular channel.

[0013] The beneficial effect of adopting the above further solution is that the first communication passage is in the form of an annular channel. There is a first annular channel on the main spool. When the main spool is in the left position, the A oil port can be communicated with the T1 oil port through the first annular channel.

[0014] Further, the first communication passage includes a first annular passage and at least one first valve port, and the first valve port is arranged on the side close to the T1 oil port.

[0015] The beneficial effect of adopting the above further solution is that both the first annular passage and the first valve port are arranged on the main spool. When the main spool is in the left position, the A oil port is communicated with the T1 oil port through the first annular passage and the first valve port. When the main spool is in the right position, the A oil port is communicated with the P1 oil port through the first annular passage. The first valve port is only used for the connection between the A oil port and the T1 oil port. The first communication passage adopts the form of cooperation between the annular passage and the valve port. The valve port is smaller than the annular passage, and it is easier to achieve precise control. During oil return, the speed cannot be too fast and the amount cannot be too much to prevent air suction. The valve port can be selected according to specific conditions. For example, two first valve ports can be arranged. The two first valve ports can be symmetrically arranged.

[0016] Further, a second communication passage for communicating the B oil port with the T2 oil port is provided on the main spool when the main spool is in the left position.

[0017] The beneficial effect of adopting the above further solution is that the second communication passage can meet the requirement of the oil path connection between the B oil port and the T2 oil port when the main spool is in the left position.

[0018] Further, the second communication passage includes a second annular passage.

[0019] The beneficial effect of adopting the above further solution is that the second communication passage can adopt the form of an annular passage. There is a second annular passage on the main spool. When the main spool is in the left position, the B oil port can be communicated with the T2 oil port through the second annular passage.

[0020] Further, the second communication passage includes a second annular passage and at least one second valve port, and the second valve port is arranged on the side close to the T2 oil port.

[0021] The beneficial effect of adopting the above further solution is that both the second annular passage and the second valve port are arranged on the main spool. When the main spool is in the left position, the B oil port is communicated with the T2 oil port through the second annular passage and the second valve port. The second communication passage can also adopt the form of cooperation between the annular passage and the valve port. The valve port is smaller than the annular passage, and it is easier to achieve precise control. During oil return, the speed cannot be too fast and the amount cannot be too much to prevent air suction.

[0022] Further, a third annular passage for communicating the P2 oil port with the B oil port is also provided on the main spool when the main spool is in the right position, and the third annular passage is arranged on the left side of the second annular passage.

[0023] The beneficial effect of adopting the above further solution is that there is a third annular passage on the main spool. When the main spool is in the right position, the P2 oil port can be communicated with the B oil port through the third annular passage.

[0024] Further, a guide rod portion for positioning the spring is provided on the limiting piston.

[0025] The beneficial effect of adopting the above further scheme is that the right end of the spring is sleeved outside the guide rod portion, which has a positioning and guiding effect on the spring.

[0026] Further, the left valve cover is threadedly connected to the valve body, and / or the right valve cover is threadedly connected to the valve body.

[0027] The beneficial effect of adopting the above further scheme is that the valve cover is threadedly connected to the valve body, which is convenient for connection and maintenance.

[0028] Further, a sealing ring is also provided between the left valve cover and the valve body and / or between the right valve cover and the valve body.

[0029] The beneficial effect of adopting the above further scheme is to increase the connection sealing performance between the valve cover and the valve body.

[0030] The present invention also relates to a usage method of the automatic reversing two-position eight-way reversing valve based on the above.

[0031] When no hydraulic oil is introduced into the Pi1 oil port and the Pi2 oil port, when hydraulic oil is introduced into the Pi1 oil port and no hydraulic oil is introduced into the Pi2 oil port, or when hydraulic oil is introduced into both the Pi1 oil port and the Pi2 oil port, and the acting force of the hydraulic oil at the Pi2 oil port on the main spool is less than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool and the spring force of the spring, under the action of the spring force of the spring or under the combined action of the acting force of the hydraulic oil at the Pi1 oil port on the main spool and the spring force of the spring, the main spool is in the left position, and the left end of the main spool fits against the left valve cover, and the A oil port and the B oil port are respectively communicated with the T1 oil port and the T2 oil port through the passages on the main spool;

[0032] When hydraulic oil is introduced into both the Pi1 oil port and the Pi2 oil port, and the acting force of the hydraulic oil at the Pi2 oil port on the main spool is greater than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool and the spring force of the spring, the main spool moves rightward under the action of the acting force of the hydraulic oil at the Pi2 oil port on the main spool, overcoming the spring force of the spring and the acting force of the hydraulic oil at the Pi1 oil port on the main spool, the right end of the main spool fits against the right valve cover, the main spool is in the right position, and the P1 oil port and the P2 oil port are respectively communicated with the A oil port and the B oil port through the passages on the main spool;

[0033] When the main spool valve is in the right position and needs to automatically change direction, the hydraulic pressure of the Pi1 oil port is increased. The aperture of the left core hole is smaller than that of the right core hole. The acting force of the hydraulic oil at the Pi1 oil port on the main spool valve and the spring force of the spring are greater than the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve. The main spool valve is subjected to a force towards the floating piston side, causing the main spool valve in the right position to actively move to the left position for automatic direction change. At this time, the P1 oil port and the P2 oil port no longer communicate with the A oil port and the B oil port through the passages on the main spool valve, and the A oil port and the B oil port communicate with the T1 oil port and the T2 oil port respectively through the passages on the main spool valve.

[0034] The beneficial effects of the present invention are as follows: When the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve is less than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool valve and the spring force, the main spool valve does not move, that is, the main spool valve remains in the left position, and the T1 oil port and the T2 oil port communicate with the A oil port and the B oil port respectively. The pressure oil of the actuator flows into the T1 oil port and the T2 oil port, and the actuator has no action; When the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve is greater than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool valve and the spring force, the main spool valve moves to the right position, and the P1 oil port and the P2 oil port communicate with the A oil port and the B oil port respectively, and the pressure oil controls the actuator to act; When the hydraulic pressure at the Pi1 oil port increases to the point where the acting force of the hydraulic oil at the Pi1 oil port on the main spool valve and the spring force are greater than the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve, the spool valve automatically moves to the left. Without an external manual direction change structure or hydraulic oil, the main spool valve can automatically change direction, achieving intelligent control. The spool valve of the present invention can achieve automatic direction change. The direction change process can reduce the hydraulic impact of the medium on the valve body and the main spool valve. The direction change is stable and without impact, greatly improving the stability of the direction change valve. Brief Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the main spool valve of the present invention when it is in the left position;

[0036] Figure 2 It is a schematic structural diagram of the main spool valve of the present invention when it is in the right position;

[0037] Figure 3 It is a schematic structural diagram of the cooperation state of the spool valve, the piston and the spring of the present invention;

[0038] Figure 4 It is a schematic structural diagram of the main spool valve of the present invention;

[0039] Figure 5 It is a hydraulic schematic diagram of the present invention.

[0040] In the figure, 1 is the valve body; 2 is the main spool; 20 is the left core hole; 21 is the right core hole; 22 is the through hole; 23 is the first annular channel; 24 is the first valve port; 25 is the second annular channel; 26 is the second valve port; 27 is the third annular channel; 28 is the fourth annular channel; 29 is the radial hole; 3 is the floating piston; 4 is the spring; 5 is the limit piston; 51 is the guide rod part; 6 is the left valve cover; 7 is the right valve cover; 8 is the sealing ring. Specific embodiments

[0041] The principles and features of the present invention will be described below in conjunction with examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0042] As Figures 1 - 5 shown, an automatic reversing two-position eight-way reversing valve includes a valve body 1 and a main spool 2 disposed within the valve body 1. It further includes a floating piston 3, a spring 4, and a limit piston 5 disposed within the main spool 2. The valve body 1 is provided with a valve cavity for the main spool 2 to move, a left valve cover 6 and a right valve cover 7 for limiting the movement amount of the main spool 2. The main spool 2 is provided with a spool hole. The floating piston 3 and the limit piston 5 are respectively sealed at the left end and the right end of the spool hole. The floating piston 3 and the limit piston 5 are respectively slidably connected to the main spool 2. The spool hole includes a left core hole 20 for accommodating the floating piston 3 and a right core hole 21 for accommodating the spring 4 and the limit piston 5. The left core hole 20 is communicated with the right core hole 21 through a through hole 22. The aperture of the left core hole 20 is smaller than the aperture of the right core hole 21;

[0043] The valve body 1 is further provided with a P1 oil port, a P2 oil port, an A oil port, a B oil port, a T1 oil port, a T2 oil port, a Pi1 oil port, and a Pi2 oil port. The Pi1 oil port is disposed in the middle of the valve cavity and is communicated with the right core hole 21. The Pi2 oil port is disposed at the left end of the valve cavity;

[0044] When the hydraulic force of the Pi2 oil port on the main spool 2 is less than the sum of the hydraulic force of the Pi1 oil port on the main spool 2 and the spring force of the spring 4, the main spool 2 is in the left position, and the A oil port is communicated with the T1 oil port, and the B oil port is communicated with the T2 oil port; when the hydraulic force of the Pi2 oil port on the main spool 2 is greater than the sum of the hydraulic force of the Pi1 oil port on the main spool 2 and the spring force of the spring 4, the main spool 2 is in the right position, and the P1 oil port is communicated with the A oil port, and the P2 oil port is communicated with the B oil port.

[0045] The Pi1 oil port is communicated with the right core hole 21 through an oil path. The oil path includes a fourth annular channel 28. The fourth annular channel 28 is communicated with the right core hole 21 through at least one radial hole 29.

[0046] The left or right position of the main spool corresponds to the left or right position of the structural diagram.

[0047] A first communication passage for connecting the A oil port and the T1 oil port when the main spool 2 is in the left position is provided on the main spool 2. The first communication passage is used to connect the P1 oil port and the A oil port when the main spool 2 is in the right position. The first communication passage is provided on the main spool 2, which not only meets the requirement that the A oil port can be connected to the T1 oil port through the first communication passage when the main spool 2 is in the left position, but also meets the requirement that the P1 oil port can be connected to the A oil port through the first communication passage when the main spool 2 is in the right position.

[0048] The first communication passage includes a first annular channel 23. The first communication passage adopts an annular channel form. There is a first annular channel 23 on the main spool 2. When the main spool 2 is in the left position, the A oil port can be connected to the T1 oil port through the first annular channel 23.

[0049] The first communication passage includes a first annular channel 23 and at least one first valve port 24. The first valve port 24 is arranged on the side close to the T1 oil port. Both the first annular channel 23 and the first valve port 24 are arranged on the main spool 2. When the main spool 2 is in the left position, the A oil port is connected to the T1 oil port through the first annular channel 23 and the first valve port 24. When the main spool 2 is in the right position, the A oil port is connected to the P1 oil port through the first annular channel 23. The first valve port is only used to connect the A oil port and the TI oil port. The first communication passage adopts a form of cooperation between an annular channel and a valve port. The valve port is smaller than the annular channel, which is easier to achieve precise control. When returning oil, it cannot be too fast or too much to prevent air suction.

[0050] The first valve port can be selected according to specific conditions. For example, two first valve ports 24 can be provided. The two first valve ports 24 can be symmetrically arranged.

[0051] A second communication passage for connecting the B oil port and the T2 oil port when the main spool 2 is in the left position is provided on the main spool 2. The second communication passage can meet the requirement of the oil circuit connection between the B oil port and the T2 oil port when the main spool 2 is in the left position.

[0052] The second communication passage includes a second annular channel 25. The second communication passage adopts an annular channel form. There is a second annular channel 25 on the main spool 2. When the main spool 2 is in the left position, the B oil port can be connected to the T2 oil port through the second annular channel 25.

[0053] The second communication passage includes a second annular passage 25 and at least one second valve port 26. The second valve port 26 is arranged close to the side of the T2 oil port. Both the second annular passage 25 and the second valve port 26 are arranged on the main spool 2. When the main spool 2 is in the left position, the B oil port is communicated with the T2 oil port through the second annular passage 25 and the second valve port 26. The second communication passage adopts a form of cooperation between an annular passage and a valve port. The valve port is smaller than the annular passage, making it easier to achieve precise control. During oil return, the speed and amount cannot be too fast or too much to prevent air suction.

[0054] The second valve port can be selected according to specific circumstances. For example, two second valve ports 26 can be arranged. The two second valve ports 26 can be symmetrically arranged.

[0055] A third annular passage 27 for communicating the P2 oil port with the B oil port is further arranged on the main spool 2 when the main spool 2 is in the right position. The third annular passage 27 is arranged on the left side of the second annular passage 25. There is a third annular passage 27 on the main spool 2. When the main spool 2 is in the right position, the P2 oil port can be communicated with the B oil port through the third annular passage 27.

[0056] A guide rod portion 51 for positioning the spring 4 is arranged on the limiting piston 5. The right end of the spring 4 is sleeved outside the guide rod portion 51, which has a positioning and guiding effect on the spring 4.

[0057] The left valve cover 6 is threadedly connected to the valve body 1, and / or the right valve cover 7 is threadedly connected to the valve body 1. The valve cover is threadedly connected to the valve body 1, which is convenient for connection and maintenance.

[0058] A sealing ring 8 is further arranged between the left valve cover 6 and the valve body 1 and / or between the right valve cover 7 and the valve body 1. The connection tightness between the valve cover and the valve body 1 is increased.

[0059] When the hydraulic oil force on the main spool at the Pi2 oil port is greater than the sum of the hydraulic oil force on the main spool at the Pi1 oil port and the spring force of the spring, the main spool originally in the left position is in contact with the left valve cover, but not in a sealed contact. Therefore, the hydraulic oil can enter between the main spool and the left valve cover and act on the left end face of the main spool; the hydraulic oil can also enter the floating piston to act on the end face of the floating piston, thereby pushing the main spool.

[0060] The present invention also relates to a use method of the automatic reversing two-position eight-way reversing valve based on the above.

[0061] When no hydraulic oil is introduced into the Pi1 oil port and the Pi2 oil port, the main spool 2 is in the left position. Under the action of the spring force of the spring 4, the left end of the main spool 2 is in contact with the left valve cover 6. The A oil port and the B oil port are respectively communicated with the T1 oil port and the T2 oil port through the passages on the main spool 2.

[0062] Alternatively, when hydraulic oil is introduced into the Pi1 port and not into the Pi2 port, the main spool 2 is in the left position. Under the combined action of the hydraulic pressure at the Pi1 port and the spring force of the spring 4, the left end of the main spool 2 abuts against the left valve cover 6, and the A port and the B port are respectively connected to the T1 port and the T2 port through the passages on the main spool 2.

[0063] Alternatively, when hydraulic oil is introduced into both the Pi1 port and the Pi2 port, and the acting force of the hydraulic oil at the Pi2 port on the main spool is less than the sum of the acting force of the hydraulic oil at the Pi1 port on the main spool and the spring force of the spring, the main spool 2 is in the left position. Under the combined action of the hydraulic pressure at the Pi1 port and the spring force of the spring 4, the left end of the main spool 2 abuts against the left valve cover 6, and the A port and the B port are respectively connected to the T1 port and the T2 port through the passages on the main spool 2.

[0064] When hydraulic oil is introduced into both the Pi1 port and the Pi2 port and the acting force of the hydraulic oil at the Pi2 port on the main spool is greater than the sum of the acting force of the hydraulic oil at the Pi1 port on the main spool and the spring force of the spring 4, the main spool moves rightward under the action of the hydraulic pressure at the Pi2 port, overcoming the spring force of the spring 4 and the hydraulic pressure at the Pi1 port. The right end of the main spool 2 abuts against the right valve cover 7, and the main spool 2 is in the right position. At this time, the P1 port and the P2 port are respectively connected to the A port and the B port through the passages on the main spool 2.

[0065] When the main spool 2 needs to automatically reverse while in the right position, increase the hydraulic pressure at the Pi1 port. The diameter of the left core hole 20 is smaller than the diameter of the right core hole 21, as Figure 4 shown in D2 < D1. The acting force of the hydraulic oil at the Pi1 port on the main spool and the spring force of the spring are greater than the acting force of the hydraulic oil at the Pi2 port on the main spool. The main spool 2 is subjected to a force towards the floating piston 3 side, causing the main spool 2 in the right position to actively move to the left position to achieve automatic reversal. At this time, the P1 port and the P2 port are no longer respectively connected to the A port and the B port through the passages on the main spool 2. The A port and the B port are respectively connected to the T1 port and the T2 port through the passages on the main spool 2.

[0066] When the force exerted by the hydraulic oil at the Pi2 port on the main spool is less than the sum of the force exerted by the hydraulic oil at the Pi1 port on the main spool and the spring force, the main spool does not move, that is, the main spool remains in the left position, and the T1 port and the T2 port are respectively connected to the A port and the B port. The pressure oil of the actuator flows into the T1 port and the T2 port, and the actuator does not operate. When the force exerted by the hydraulic oil at the Pi2 port on the main spool is greater than the sum of the force exerted by the hydraulic oil at the Pi1 port on the main spool and the spring force, the main spool moves to the right position, and the P1 port and the P2 port are respectively connected to the A port and the B port, and the pressure oil controls the actuator to operate. When the hydraulic pressure at the Pi1 port increases to the point where the sum of the force exerted by the hydraulic oil at the Pi1 port on the main spool and the spring force is greater than the force exerted by the hydraulic oil at the Pi2 port on the main spool, the spool automatically moves to the left. In the absence of an external manual reversing structure or hydraulic oil, the main spool can automatically reverse, achieving intelligent control. The present invention controls the automatic reversal of the main spool by controlling the internal pressure magnitude. After the internal pressure increases, the automatic reversal of the main spool can be achieved, thereby realizing the purpose of intelligent control of the reversing valve.

[0067] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An automatic reversing two-position eight-way reversing valve, comprising a valve body (1) and a main spool (2) disposed within the valve body (1), characterized in that, It further includes a floating piston (3), a spring (4) and a limit piston (5) arranged in the main spool valve (2). A valve cavity for the movement of the main spool valve (2), a left valve cover (6) and a right valve cover (7) for limiting the movement amount of the main spool valve (2) are provided on the valve body (1). A spool hole is provided in the main spool valve (2). The floating piston (3) and the limit piston (5) are respectively and sealingly arranged at the left end and the right end of the spool hole. The floating piston (3) and the limit piston (5) are respectively slidably connected to the main spool valve (2). The spool hole includes a left core hole (20) for accommodating the floating piston (3) and a right core hole (21) for accommodating the spring (4) and the limit piston (5). The left core hole (20) is communicated with the right core hole (21) through a through hole (22). The aperture of the left core hole (20) is smaller than that of the right core hole (21). The valve body (1) is further provided with a P1 oil port, a P2 oil port, an A oil port, a B oil port, a T1 oil port, a T2 oil port, a Pi1 oil port and a Pi2 oil port. The Pi1 oil port is arranged in the middle of the valve cavity and is communicated with the right core hole (21). The Pi2 oil port is arranged at the left end of the valve cavity. When the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve (2) is less than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool valve (2) and the spring force of the spring (4), the main spool valve (2) is in the left position, the A oil port is communicated with the T1 oil port, and the B oil port is communicated with the T2 oil port. When the acting force of the hydraulic oil at the Pi2 oil port on the main spool valve (2) is greater than the sum of the acting force of the hydraulic oil at the Pi1 oil port on the main spool valve (2) and the spring force of the spring (4), the main spool valve (2) is in the right position, the P1 oil port is communicated with the A oil port, and the P2 oil port is communicated with the B oil port. The main spool valve (2) is provided with a first communication passage for communicating the A oil port with the T1 oil port when the main spool valve (2) is in the left position. The first communication passage is used for communicating the P1 oil port with the A oil port when the main spool valve (2) is in the right position. The first communication passage includes a first annular channel (23) and at least one first valve port (24). The first valve port (24) is arranged on the side close to the T1 oil port. The main spool valve (2) is provided with a second communication passage for communicating the B oil port with the T2 oil port when the main spool valve (2) is in the left position. The second communication passage includes a second annular channel (25) and at least one second valve port (26).

2. The two-position eight-way reversing valve with automatic commutation according to claim 1, wherein The main spool valve (2) is further provided with a third annular channel (27) for communicating the P2 oil port with the B oil port when the main spool valve (2) is in the right position. The third annular channel (27) is arranged on the left side of the second annular channel (25).

3. The two-position eight-way reversing valve with automatic commutation according to claim 1, characterized in that, The limit piston (5) is provided with a guide rod portion (51) for positioning the spring (4).

4. The two-position eight-way reversing valve with automatic commutation according to claim 1, characterized in that, The left valve cover (6) is threadedly connected to the valve body (1), and / or the right valve cover (7) is threadedly connected to the valve body (1).

5. The two-position eight-way reversing valve with automatic commutation according to claim 4, characterized in that, A sealing ring (8) is also provided between the left valve cover (6) and the valve body (1) and / or between the right valve cover (7) and the valve body (1).

6. A method for using an automatic reversing two-position eight-way reversing valve according to any one of claims 1-5, characterized in that when no hydraulic oil is introduced into the Pi1 oil port and the Pi2 oil port, or when hydraulic oil is introduced into the Pi1 oil port and no hydraulic oil is introduced into the Pi2 oil port, or when hydraulic oil is introduced into both the Pi1 oil port and the Pi2 oil port, and the acting force of the hydraulic oil in the Pi2 oil port on the main spool (2) is less than the sum of the acting force of the hydraulic oil in the Pi1 oil port on the main spool (2) and the spring force of the spring, under the action of the spring force of the spring (4) or under the combined action of the acting force of the hydraulic oil in the Pi1 oil port on the main spool (2) and the spring force of the spring (4), the main spool (2) is in the left position, the left end of the main spool (2) is in contact with the left valve cover (6), and the A oil port and the B oil port are respectively communicated with the T1 oil port and the T2 oil port through the passages on the main spool (2); when hydraulic oil is introduced into both the Pi1 oil port and the Pi2 oil port, and the acting force of the hydraulic oil in the Pi2 oil port on the main spool (2) is greater than the sum of the acting force of the hydraulic oil in the Pi1 oil port on the main spool (2) and the spring force of the spring (4), the main spool (2) moves rightward under the action of the hydraulic pressure in the Pi2 oil port, overcoming the spring force of the spring (4) and the hydraulic pressure in the Pi1 oil port, the right end of the main spool (2) is in contact with the right valve cover (7), the main spool (2) is in the right position, and the P1 oil port and the P2 oil port are respectively communicated with the A oil port and the B oil port through the passages on the main spool (2); when the main spool (2) needs to automatically reverse in the right position, the acting force of the hydraulic oil in the Pi1 oil port on the main spool (2) is increased. The aperture of the left core hole (20) is smaller than the aperture of the right core hole (21). The hydraulic pressure in the Pi1 oil port and the spring force of the spring are greater than the hydraulic pressure in the Pi2 oil port. The main spool (2) is subjected to a force towards the floating piston (3) side, so that the main spool (2) in the right position actively moves to the left position for automatic reversing. At this time, the P1 oil port and the P2 oil port are no longer communicated with the A oil port and the B oil port through the passages on the main spool (2), and the A oil port and the B oil port are respectively communicated with the T1 oil port and the T2 oil port through the passages on the main spool (2).

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