Commutating union with load holding and hydraulic system

Abstract

The present invention relates to a hydraulic valve, and provides a commutation union for load holding, which includes a main valve, a first holding valve, a second holding valve, and a holding pilot valve. The main valve includes a main spool and a main valve chamber. The main spool can move within the main valve chamber under the control of hydraulic oil at a first control oil port and a second control oil port, so as to control the communication state between a first working oil port and a second working oil port, an oil inlet, and an oil return port. The first holding valve is located between the second working oil port and the main valve to be able to block the oil path therebetween. The second holding valve is arranged on a pressure relief oil path connected to the control end of the first holding valve, and the control end of the second holding valve is connected to the holding pilot valve to be able to block the pressure relief oil path connected to the control end of the first holding valve under the control of the holding pilot valve. Through the double sealing formed by the first holding valve and the second holding valve, the leakage risk is greatly reduced, and the load holding performance is improved. The present invention also provides a hydraulic system.

Description

Technical Field

[0001] The present invention relates to a hydraulic valve, and more particularly to a directional spool with load holding. In addition, the present invention also relates to a hydraulic system. Background Art

[0002] Currently, with the rapid development of excavators, people's requirements for the performance of excavators are becoming increasingly strict. Since the boom of an excavator is not allowed to have excessive settlement when it is stationary, the load holding performance of the excavator is an important indicator, which requires that the leakage of the directional spool of the excavator be low when it is in the neutral position.

[0003] To solve the leakage problem, in the prior art, usually the clearance between the valve stem and the valve hole is reduced. However, this method has extremely high requirements for the machining accuracy of the valve hole and the valve stem, and too small a clearance is likely to cause the valve stem to jam. In addition, a load holding valve can also be installed between the oil cylinder and the main spool, and the oil circuit is cut off by a conical seal to reduce leakage.

[0004] An existing directional spool with a holding valve is as Figure 1 shown. The existing directional spool mainly consists of a valve body 9, a main spool 10, a relief valve 11, an end cap 12, a main spool return spring 13, a check valve 14, a compensation valve 15, a holding valve, etc. Among them, the holding valve has a two-stage structure of a main holding valve and a pilot holding control valve. The main holding valve mainly consists of a 1 holding spool, a 2 holding spool return spring, and a 3 holding valve positioning plug. The pilot holding valve mainly consists of a 4 pilot valve plug, a 5 pilot spool return spring, a 6 pilot spool, and a 7 pilot valve sleeve. The working principle of this directional spool is as Figure 2 shown, and the specific description is as follows: The main spool 10 controls the movement direction of the actuator under the action of the pilot signals pa1 and pb1; the relief valve 11 plays an overload protection role; the check valve 14 prevents the oil from flowing back; the compensation valve 15 maintains the pressure difference before and after the main spool 10 unchanged, so that the movement speed of the actuator is only controlled by the opening area of the main spool. When the directional valve is in the neutral position, the oil circuits between P, A, B, and T are cut off by the main spool 10. At the same time, the conical seal between the holding spool 1 and the valve body 9 blocks the leakage of oil from the load B port to the main spool 10, and the load remains stationary in the neutral position; when the pa1 signal is given, the main spool 10 moves to the left, and the holding spool 1 opens forward, and the oil circuits between P and A, and B and T are connected, and the load rises; when the pb1 signal is given, at the same time, a control oil port signal is also given to the pilot holding valve, the main spool 10 moves to the right, the pilot holding valve changes direction, and the holding valve opens in the reverse direction, and the oil circuits between P and B, and A and T are connected, and the load descends.

[0005] The holding pilot valve in the commutation union of the above prior art is a separate valve block installed on the valve body, with many parts, complex structure and large volume. Due to the limited installation space of the small mechanical multi-way valve, its assembly space is too compact, making installation difficult. Moreover, the control oil port and drain oil port of the pilot valve need to be externally connected to the oil circuit through oil pipes, resulting in a messy oil circuit of the multi-way valve, which is not convenient for pre-assembly and subsequent maintenance and repair.

[0006] In addition, the commutation union gradually fails to meet the index requirements of the excavator for the load holding performance. Therefore, how to further improve the load holding performance of the commutation union is also an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a commutation union with load holding, which has good load holding performance, is structurally compact and has few externally connected oil circuits.

[0008] Another technical problem to be solved by the present invention is to provide a hydraulic system that can hold the load when the hydraulic actuator is in the neutral position, is structurally compact and has few externally connected oil circuits.

[0009] To solve the above technical problems, the present invention provides a commutation union with load holding, which is characterized in that it includes a valve body provided with an oil inlet, an oil return port, a first working oil port, a second working oil port, a first control oil port and a second control oil port. A main valve, a first holding valve, a second holding valve and a holding pilot valve are arranged inside the valve body. The main valve includes a main spool and a main valve cavity. The movement of the main spool in the main valve cavity is controlled by the hydraulic oil through the first control oil port and the second control oil port. The movement stroke range of the main spool at least includes a first working position and a second working position for controlling the hydraulic actuator to move in opposite directions to each other, and a neutral position located between the first working position and the second working position. In the state where the main spool is in the first working position, the first working oil port is communicated with the oil inlet, and the second working oil port is communicated with the oil return port; in the state where the main spool is in the neutral position, the oil inlet, the oil return port, the first working oil port and the second working oil port are mutually cut off; in the state where the main spool is in the second working position, the second working oil port is communicated with the oil inlet, and the first working oil port is communicated with the oil return port; the first holding valve is located between the second working oil port and the main valve to be able to block the oil circuit between the second working oil port and the main valve when the main spool is in the neutral position. The second holding valve is arranged on the unloading oil circuit connected to the control end of the first holding valve, and the control end of the second holding valve is connected to the holding pilot valve to be able to block the unloading oil circuit connected to the control end of the first holding valve under the control of the holding pilot valve.

[0010] Preferably, the unloading oil circuit connected to the control end of the first holding valve is connected to the main valve. When the main valve core is in the first working position, the unloading oil circuit is connected to the return oil port. When the main valve core is in the middle position or the second working position, the unloading oil circuit is cut off.

[0011] Preferably, a compensation valve is further provided inside the valve body, and the compensation valve is connected to the main valve to control the pressure difference before and after the main valve to be constant.

[0012] Preferably, the main valve chamber includes a first spring chamber, a first oil return chamber, a first working chamber, a first pressure compensation chamber, an oil inlet chamber, a second pressure compensation chamber, a third pressure compensation chamber, a second working chamber, a second oil return chamber and a second spring chamber, the first spring chamber is connected to the first control oil port, the second spring chamber is connected to the second control oil port, the first oil return chamber and the second oil return chamber are both connected to the oil return port, the oil inlet chamber is connected to the oil inlet, the first pressure compensation chamber, the second pressure compensation chamber and the third pressure compensation chamber are all connected to the compensation valve, the first working chamber is connected to the first working oil port, and the second working chamber is connected to the first holding valve, wherein, when the main valve core is in the first working position, the oil inlet chamber is connected to the second pressure compensation chamber, the first working chamber is connected to the second pressure compensation chamber, and the second working chamber is connected to the first holding valve. A pressure compensation chamber is communicated with the first working chamber, and the second oil return chamber is communicated with the second working chamber and the second holding valve; when the main valve core is in the second working position, the oil inlet chamber is communicated with the second pressure compensation chamber, the third pressure compensation chamber is communicated with the second working chamber, the oil circuit between the first oil return chamber and the first working chamber is connected, and the oil circuit between the second oil return chamber and the second holding valve is cut off; when the main valve core is in the neutral position, the oil circuit between the oil inlet chamber and the second pressure compensation chamber is cut off, the oil circuit between the first working chamber and the first oil return chamber and the first pressure compensation chamber is cut off, the second working chamber is not communicated with the third pressure compensation chamber and the second oil return chamber, and the oil circuit between the second oil return chamber and the second holding valve is cut off.

[0013] Preferably, the first holding valve includes a first holding valve core, a first holding valve return spring, a first holding valve oil inlet connected to the second working chamber, a first holding valve oil outlet chamber connected to the second working oil port, and a first holding valve control chamber connected to the second holding valve. The first holding valve return spring is arranged in the first holding valve control chamber to be able to hold one end of the first holding valve core against the first holding valve oil inlet, forming a conical seal between the first holding valve oil inlet and the first holding valve oil outlet chamber.

[0014] Preferably, the second holding valve includes a second holding valve core, a second holding valve return spring, a second holding valve oil inlet chamber, a second holding valve oil outlet, and a second holding valve control chamber. The second holding valve return spring is disposed within the second holding valve control chamber to abut one end of the second holding valve core against the second holding valve oil outlet, forming a conical seal between the second holding valve oil outlet and the second holding valve oil inlet chamber. Inside the valve body, a first holding valve control oil passage, a second holding valve control oil passage, and a second holding valve oil drain passage are formed. The first holding valve control oil passage connects the first holding valve control chamber and the second holding valve oil inlet chamber. The second holding valve control oil passage connects the second holding valve control chamber and the holding pilot valve. The second holding valve oil drain passage connects the second holding valve oil outlet and the main valve chamber. Wherein, when the main valve core is in the first working position state, the second holding valve oil drain passage communicates with the second oil return chamber. When the main valve core is in the second working position or the neutral position state, the main valve core blocks the connection between the second holding valve oil drain passage and the second oil return chamber.

[0015] Preferably, the holding pilot valve includes a holding pilot valve core and a holding pilot valve chamber. The holding pilot valve chamber includes a pilot valve signal oil chamber communicating with the first control oil port, a pilot valve oil inlet chamber communicating with the second holding valve control oil passage, and a pilot valve oil drain chamber communicating with the oil return port. The hydraulic oil at the first control oil port controls the movement of the holding pilot valve core within the holding pilot valve chamber to communicate the pilot valve oil inlet chamber and the pilot valve oil drain chamber.

[0016] Preferably, a check valve is provided between the compensation valve and the main valve.

[0017] Preferably, a first relief valve and a second relief valve are respectively provided between the first working oil port and the oil return port and between the second working oil port and the oil return port.

[0018] Furthermore, the present invention also provides a hydraulic system including the reversing union with load holding according to any one of the above technical solutions.

[0019] Through the above solutions, the beneficial effects of the present invention are as follows:

[0020] The reversing union with load holding of the present invention is serially arranged with two holding valves to form a double seal, greatly reducing the leakage risk, minimizing leakage, and having better load holding performance. Moreover, the holding pilot valve is disposed inside the valve body, reducing the number of parts, making the structure of the reversing union simpler and more compact, and reducing the overall volume and weight of the valve body. At the same time, the connecting oil passages between the various hydraulic structures are all disposed inside the valve body, eliminating the need for external oil pipes, simplifying the external oil circuit of the reversing union, and making the pre-assembly and subsequent maintenance and servicing more convenient and efficient.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed implementation, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0023] Figure 1 is a schematic structural diagram of an existing commutation union;

[0024] Figure 2 is a hydraulic schematic diagram of an existing commutation union;

[0025] Figure 3 is a hydraulic schematic diagram of the commutation union with load holding of the present invention;

[0026] Figure 4 is a schematic structural diagram of the commutation union with load holding of the present invention;

[0027] Figure 5 is an enlarged partial structural diagram of the commutation union with load holding of the present invention;

[0028] Figure 6 is a schematic structural diagram of the first holding spool of the present invention;

[0029] Figure 7 is a schematic structural diagram of the holding pilot spool of the present invention.

[0030] DESCRIPTION OF THE REFERENCE NUMERALS

[0031] DETAILED IMPLEMENTATION

[0032] The following will describe in detail the detailed implementation of the present invention with reference to the drawings. It should be understood that the detailed implementation described herein is only used to illustrate and explain the present invention, and the protection scope of the present invention is not limited to the following detailed implementation.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "formed", "provided with", "arranged", "connected", etc. shall be understood in a broad sense. For example, the connection can be a direct connection, or an indirect connection through an intermediate medium, and can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate connecting member, and can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, without corresponding explanation, the orientation terms "left", "right", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. What is touched is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention; for the orientation terms of the present invention, they should be understood in combination with the actual installation state.

[0035] The terms "first", "second", "third" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", "third" may explicitly or implicitly include one or more of the said features.

[0036] Such as Figures 3 to 4As shown, a specific embodiment of the commutation union with load holding of the present invention includes a valve body 1 provided with an oil inlet P, an oil return port T, a first working oil port A, a second working oil port B, a first control oil port a, and a second control oil port b. The oil inlet P is used to externally connect the hydraulic pump of the hydraulic system, the oil return port T is used to externally connect the oil return tank of the hydraulic system, the first working oil port A and the second working oil port B are used to connect the hydraulic actuator, and the first control oil port a and the second control oil port b are respectively used to connect different control oil circuits in the hydraulic system. Inside the valve body 1, there are a main valve 2, a first holding valve 3, a second holding valve 4, and a holding pilot valve 5. The main valve 2 includes a main spool 21 and a main valve cavity 22. The first control oil port a and the second control oil port b are respectively connected to both ends of the main valve cavity 22 through oil channels provided inside the valve body 1. The hydraulic oil through the first control oil port a and the second control oil port b controls the movement of the main spool 21 within the main valve cavity 22. The movement stroke range of the main spool 21 at least includes a first working position and a second working position for controlling the hydraulic actuator to move in opposite directions to each other, and a neutral position located between the first working position and the second working position. Among them, when the main spool 21 is in the first working position state, the first working oil port A is communicated with the oil inlet P, and the second working oil port B is communicated with the oil return port T; when the main spool 21 is in the neutral position state, the oil inlet P, the oil return port T, the first working oil port A, and the second working oil port B are mutually cut off; when the main spool 21 is in the second working position state, the second working oil port B is communicated with the oil inlet P, and the first working oil port A is communicated with the oil return port T. By switching the communication states of the first working oil port A with the oil inlet P and the oil return port T, and the communication states of the second working oil port B with the oil inlet P and the oil return port T through the main spool 2, the working states of the hydraulic actuators on the first working oil port A and the second working oil port B are controlled; the first holding valve 3 is located between the second working oil port B and the main valve 2 to be able to block the oil circuit between the second working oil port B and the main valve 2 when the main spool 21 is in the neutral position state. The second holding valve 4 is arranged on the unloading oil circuit connected to the control end of the first holding valve 3, and the control end of the second holding valve 4 is connected to the holding pilot valve 5 to be able to block the unloading oil circuit connected to the control end of the first holding valve 3 under the control of the holding pilot valve 5.When the main spool 21 is in the neutral position, the second working oil port B is cut off from both the oil inlet port P and the oil return port T. By maintaining the pilot valve 5 to control the spool position of the second holding valve 4, a tapered seal of the internal oil passage of the second holding valve 4 is formed, so that the control end of the first holding valve 3 cannot unload the oil pressure through the unloading oil passage. The spool position of the first holding valve 3 always remains in the closed state, ensuring the tapered seal of the internal oil passage of the first holding valve 3 to block the oil passage between the second working oil port B and the main valve 2, preventing the hydraulic oil at the second working oil port B from leaking to the oil return port T through the gap between the main spool 21 and the main valve cavity 22. Through the double seal formed by the first holding valve 3 and the second holding valve 4, the leakage risk is greatly reduced, and the occurrence of oil leakage is minimized, so that the reversing union with load holding of the present invention has better load holding performance.

[0037] As a specific embodiment of the reversing union with load holding of the present invention, refer to Figure 3 and Figure 4 , the unloading oil passage connected to the control end of the first holding valve 3 is connected to the main valve 2. When the main spool 21 is in the first working position, the unloading oil passage is communicated with the oil return port T. When the main spool 21 is in the neutral or second working position, the unloading oil passage is cut off. By controlling the movement of the main spool 21 in the main valve cavity 22, the on-off of the unloading oil passage and the oil return port T can be synchronously controlled.

[0038] As a preferred embodiment of the reversing union with load holding of the present invention, refer to Figure 3 and Figure 4 , a compensation valve 9 is further provided inside the valve body 1. The compensation valve 9 is connected to the main valve 2 and is used to compensate the pressure of the hydraulic oil output through the main valve 2 to control the constant pressure difference before and after the main valve 2, so that the flow rate of the hydraulic oil passing through the main valve 2 is only controlled by the opening degree of the valve port of the main spool 21, and further better control the movement speed of the hydraulic actuator, making it only affected by the opening degree of the valve port.

[0039] As a preferred embodiment of the reversing union with load holding of the present invention, refer to Figure 4, the main valve chamber 22 includes a first spring chamber 201, a first oil return chamber 202, a first working chamber 203, a first pressure compensation chamber 204, an oil inlet chamber 205, a second pressure compensation chamber 206, a third pressure compensation chamber 207, a second working chamber 208, a second oil return chamber 209 and a second spring chamber 211 arranged in sequence. The first spring chamber 201 is connected to the first control oil port a through an internal oil passage of the valve body 1, the second spring chamber 211 is connected to the second control oil port b through an internal oil passage of the valve body 1, both the first oil return chamber 202 and the second oil return chamber 209 are connected to the oil return port T through internal oil passages of the valve body 1, the oil inlet chamber 205 is connected to the oil inlet port P through an internal oil passage of the valve body 1, the first pressure compensation chamber 204, the second pressure compensation chamber 206 and the third pressure compensation chamber 207 are all connected to the compensation valve 9 through internal oil passages of the valve body 1, the first working chamber 203 is connected to the first working oil port A through an internal oil passage of the valve body 1, and the second working chamber 208 is connected to the first holding valve 3 through an internal oil passage of the valve body 1.

[0040] When control oil fluid is provided into the first spring chamber 201 through the first control oil port a to push the main spool 21 in the direction of the second spring chamber 211 and make the main spool 21 in the first working position state, the oil inlet chamber 205 is communicated with the second pressure compensation chamber 206, the first pressure compensation chamber 204 is communicated with the first working chamber 203, and the second oil return chamber 209 is communicated with the second working chamber 208 and the second holding valve 4; the hydraulic oil at the oil inlet port P can flow through the oil inlet chamber 205 and the second pressure compensation chamber 206 in sequence to flow into the compensation valve 9 for pressure compensation, the pressure-compensated hydraulic oil flows to the first pressure compensation chamber 204, and flows to the first working oil port A through the first working chamber 203 to supply oil to the hydraulic actuator. At the same time, the holding pilot valve 5 controls the spool of the second holding valve 4 to open, the hydraulic oil at the control end of the first holding valve 3 can flow through the second holding valve 4 to the second oil return chamber 209, and flow into the oil return port T to complete unloading, so that the spool of the first holding valve 3 opens, and the hydraulic actuator returns oil to the first holding valve 3 through the second working oil port B, and flows through the second working chamber 208 and the second oil return chamber 209 in sequence through the first holding valve 3 to flow to the oil return port T for oil return.

[0041] When control oil is supplied into the second spring chamber 211 through the second control oil port b to push the main spool 21 to move in the direction of the first spring chamber 201, so that the main spool 21 is in the second working position state, the oil inlet chamber 205 is communicated with the second pressure compensation chamber 206, the third pressure compensation chamber 207 is communicated with the second working chamber 208, the oil path between the first oil return chamber 202 and the first working chamber 203 is conducted, and the oil path between the second oil return chamber 209 and the second holding valve 4 is cut off; the hydraulic oil at the oil inlet port P can sequentially pass through the oil inlet chamber 205 and the second pressure compensation chamber 206 to flow into the compensation valve 9 for pressure compensation, the compensated hydraulic oil flows to the third pressure compensation chamber 207, and flows to the first holding valve 3 through the second working chamber 208. The hydraulic oil pushes the spool of the first holding valve 3 to open, and the hydraulic oil passing through the first holding valve 3 flows to the second working oil port B to supply oil to the hydraulic actuator. At the same time, the hydraulic actuator sequentially flows through the first working chamber 203 and the first oil return chamber 202 through the first working oil port A to flow back to the oil return port T for oil return.

[0042] When the main spool 21 is in the neutral position, the oil path between the oil inlet chamber 205 and the second pressure compensation chamber 206 is cut off, the oil paths between the first working chamber 203 and the first oil return chamber 202 and the first pressure compensation chamber 204 are cut off, the second working chamber 208 is not communicated with the third pressure compensation chamber 207 and the second oil return chamber 209, the oil path between the second oil return chamber 209 and the second holding valve 4 is cut off, and the spool of the second holding valve 4 is closed to keep the spool of the first holding valve 3 in the closed state, forming a double seal.

[0043] As a preferred embodiment of the reversing union with load holding of the present invention, refer to Figure 4 and Figure 5, the first holding valve 3 includes a first holding valve core 31, a first holding valve return spring 32, a first holding valve oil inlet 33 communicating with the second working chamber 208, a first holding valve oil outlet chamber 34 communicating with the second working oil port B, and a first holding valve control chamber 35 connected to the second holding valve 4. The first holding valve return spring 32 and the first holding valve core 31 are both installed in the cavity of the valve body 1, and a plug is installed at the opening of the cavity to form a seal. The first holding valve oil inlet 33 and the first holding valve control chamber 35 are respectively located at both ends of the first holding valve core 31. The first holding valve return spring 32 is disposed in the first holding valve control chamber 35 so as to be able to abut one end of the first holding valve core 31 against the first holding valve oil inlet 33, thereby abutting the conical sealing surface at the end of the first holding valve core 31 against the edge of the first holding valve oil inlet 33 to form a conical seal between the first holding valve oil inlet 33 and the first holding valve oil outlet chamber 34, which can well prevent oil leakage from the first holding valve oil outlet chamber 34 to the first holding valve oil outlet 33 and can well maintain the working state of the hydraulic actuator when the main valve 2 is in the neutral position. In addition, the first holding valve control chamber 35 is connected to the second holding valve 4, and when the valve core of the second holding valve 4 is in the closed state, the pressure of the hydraulic oil in the first holding valve control chamber 35 (i.e., the hydraulic oil at the control end of the first holding valve 3) cannot be unloaded through the unloading oil circuit, so as to ensure that the oil pressure in the first holding valve control chamber 35 will not decrease, so as to maintain the abutting state between the first holding valve core 31 and the first holding valve oil inlet 33, making the conical seal between them stable and reliable, blocking the communication between the first holding valve control chamber 35 and the second working chamber 208, and effectively preventing leakage.

[0044] As a preferred embodiment of the commutation union with load holding of the present invention, refer to Figure 4 and Figure 5, the second holding valve 4 includes a second holding valve core 41, a second holding valve return spring 42, a second holding valve oil inlet chamber 43, a second holding valve oil outlet 44, and a second holding valve control chamber 45. The second holding valve core 41 and the second holding valve return spring 42 are both installed in the cavity of the valve body 1, and a plug is installed at the opening of the cavity to form a seal. The second holding valve oil outlet 44 and the second holding valve control chamber 45 are respectively located at both ends of the second holding valve core 41. The second holding valve return spring 42 is arranged in the second holding valve control chamber 45 to be able to abut one end of the second holding valve core 41 against the second holding valve oil outlet 44, forming a conical seal between the second holding valve oil outlet 44 and the second holding valve oil inlet chamber 43. Inside the valve body 1, a first holding valve control oil passage 102, a second holding valve control oil passage 104, and a second holding valve oil drain passage 105 are formed. The first holding valve control oil passage 102 connects the first holding valve control chamber 35 and the second holding valve oil inlet chamber 43. The second holding valve oil drain passage 105 connects the second holding valve oil outlet 44 and the main valve chamber 22. The first holding valve control oil passage 102 and the second holding valve oil drain passage 105 together constitute a pressure relief oil circuit connected to the control end of the first holding valve 3. The second holding valve control oil passage 104 connects the second holding valve control chamber 45 and the holding pilot valve 5 to enable the hydraulic oil in the second holding valve control chamber 45 to be unloaded through the second holding valve control oil passage 104 under the control of the holding pilot valve 5. Among them, when the main valve core 21 is in the first working position state, the second holding valve oil drain passage 105 of the main valve core 21 communicates with the second oil return chamber 209. When the main valve core is in the second working position or the middle position state, the communication between the second holding valve oil drain passage 105 and the second oil return chamber 209 is blocked by the main valve core 21.

[0045] It should be noted that the structures of the first holding valve core 31 and the second holding valve core 41 are the same. Taking the first holding valve core 31 as an example, see Figure 4 and Figure 6, a spring hole 311 for installing the first holding valve return spring 32 is provided at one end of the first holding valve core 31, and a conical sealing surface for abutting against the first holding valve oil inlet 33 to form a conical seal is formed at the other end. A central hole 312 is provided at the bottom of the spring hole 311, and the central hole 312 is a blind hole. A damping hole 313 communicating with the central hole 312 is formed on the outer circumferential surface of the first holding valve core 31, so that the hydraulic oil in the first holding valve oil outlet cavity 34 can flow through the damping hole 313, the central hole 312 and the spring hole 311 in sequence to the first holding valve control cavity 35, so that a pressure acting on the end face of the first holding valve core 31 can be formed in the first holding valve control cavity 35, which can cancel out the pressure acting on the other end face of the first holding valve core 31 by the oil pressure in the first holding valve oil outlet cavity 34, and keep the first holding valve core 31 always abutting against the first holding valve oil inlet 33 to form a conical seal under the elastic force of the first holding valve return spring 32. When the oil pressure in the first holding valve control cavity 35 is unloaded, due to the existence of the damping hole 313, a hydraulic pressure difference is formed between the first holding valve control cavity 35 and the first holding valve oil outlet cavity 34. This hydraulic pressure difference acts on the first holding valve core 31 to form a force that pushes the first holding valve core 31 to move towards the first holding valve control cavity 35 against the elastic force of the first holding valve return spring 32, so that the first holding valve oil outlet cavity 34 is communicated with the first holding valve oil inlet 33. Since the structure of the second holding valve core 41 is the same as that of the first holding valve core 31, as a person skilled in the art, knowing the structure and working principle of the first holding valve core 31, the structure and working principle of the second holding valve core 41 should also be known, and no more elaboration will be made here.

[0046] As a preferred embodiment of the commutation union with load holding of the present invention, refer to Figure 4 and Figure 5, the holding pilot valve 5 includes a holding pilot valve spool 51 and a holding pilot valve chamber. The holding pilot valve chamber includes a pilot valve signal oil chamber 52 communicating with the first control oil port a, a pilot valve inlet oil chamber 53 communicating with the second holding valve control oil passage 104, and a pilot valve drain oil chamber 54 communicating with the oil return port T. A pilot signal oil passage 101 and a pilot drain oil passage 103 are formed inside the valve body 1. The pilot signal oil passage 101 connects the first spring chamber 201 with the pilot valve signal oil chamber 52. The hydraulic oil at the first control oil port a can flow into the pilot valve signal oil chamber 52 to control the movement of the holding pilot valve spool 51 in the holding pilot valve chamber, so that the pilot valve inlet oil chamber 53 communicates with the pilot valve drain oil chamber 54. The pilot drain oil passage 103 is connected to the oil return port T, so that the hydraulic oil in the second holding valve control chamber 45 can communicate with the oil return port T for unloading. Wherein, a pilot valve spring 55 is arranged in the holding pilot valve chamber to form a thrust pushing the holding pilot valve spool 51 towards the pilot valve signal oil chamber 52 through the pilot valve spring 55. The holding pilot valve 5 is installed inside the valve body 1, and the control oil port and the drain oil port are both connected inside the valve body 1, reducing the number of parts, making the commutation connection structure with load of the present invention simpler and more compact, reducing the overall volume and weight, saving the assembly space, and reducing the assembly difficulty.

[0047] It should be noted that, referring to Figure 4 and Figure 7 , the holding pilot valve spool 51 includes a control seal part 511, a channel part 512, a conical seal part 513 and a spring installation part 514 arranged in sequence. The control seal part 511 is located between the pilot valve signal oil chamber 52 and the pilot valve inlet oil chamber 53 to isolate the two from each other. The channel part 512 is located between the pilot valve inlet oil chamber 53 and the pilot valve drain oil chamber 54 to form a flow oil passage for their communication. The conical seal part 513 is located in the pilot valve drain oil chamber 54. The pilot valve spring 55 is installed on the spring installation part 514 to form an elastic force pushing the holding pilot valve spool 51 towards the pilot valve signal oil chamber 52, and further abut the conical seal part 513 against the end face of the pilot valve drain oil chamber 54 close to the pilot valve inlet oil chamber 53 for conical sealing between the pilot valve inlet oil chamber 53 and the flow oil passage; when pilot oil is input at the first control oil port a, the pilot oil can enter the pilot valve signal oil chamber 52 to push the holding pilot valve spool 51 towards the pilot valve drain oil chamber 54, so that the pilot valve inlet oil chamber 53 communicates with the flow oil passage.

[0048] Specifically, when there is control pressure at the first control oil port a, the main spool 21 moves towards the second control oil port b to be in the first working position, and the hydraulic oil at the first control oil port a flows into the pilot valve signal oil chamber 52 through the pilot signal oil passage 101, thereby pushing the holding pilot spool 51 to move in the direction of the pilot valve spring 55. The hydraulic oil in the second holding valve control chamber 45 can return oil to the oil return port T through the second holding valve control oil passage 104 for unloading, thereby controlling the movement of the second holding spool 41, making the first holding valve control oil passage 102 communicate with the second holding valve oil unloading passage 105, so that the hydraulic oil in the first holding valve control chamber 35 flows through the first holding valve control oil passage 102, the second holding valve 4, the second holding valve oil unloading passage 105, and the second oil return chamber 209 in sequence to return oil to the oil return port T for unloading, and further controlling the movement of the first holding spool 31 to achieve the communication between the second working oil port B and the second working chamber 208 for the second working oil port B to return oil; when there is no control pressure at the first control oil port a, that is, the main spool 21 is in the second working position or the neutral position, the oil passage between the second holding valve oil unloading passage 105 and the second oil return chamber 209 is blocked by the main spool 21. The holding pilot spool 51 returns to its original position under the elastic force of the pilot valve spring 55, blocking the second holding valve control oil passage 104 and the pilot oil unloading passage 103. Therefore, the spools of the first holding valve 3 and the second holding valve 4 are both in the closed state. When the main spool 21 is in the second working position, the high-pressure oil flowing from the oil inlet P to the second working chamber 208 can push open the first holding spool 31 to supply oil to the second working port B. When the main spool 21 is in the neutral position, the second working chamber 208 is cut off from the oil inlet P. Therefore, the spools of the first holding valve 3 and the second holding valve 4 are always in the closed state under the action of the spring force and the oil pressure to form a double seal.

[0049] As a preferred embodiment of the commutation union with load holding of the present invention, refer to Figure 4 , a check valve 8 is arranged between the compensation valve 9 and the main valve 2 to prevent the hydraulic oil in the main valve 2 from flowing back to the compensation valve 9. Specifically, the compensation valve 9 includes a compensation spool 91 and a compensation valve chamber. The compensation valve chamber includes a compensation valve oil inlet chamber 92 communicating with the second pressure compensation chamber 206, and a compensation chamber oil outlet chamber 93 communicating with the first pressure compensation chamber 204 and the third pressure compensation chamber 207 respectively. When the oil inlet P supplies oil to the second pressure compensation chamber 206, the change in the oil pressure in the second pressure compensation chamber 206 will cause the compensation spool 91 to move in the compensation valve chamber, thereby controlling the oil flow rate between the compensation valve oil inlet chamber 92 and the compensation chamber oil outlet chamber 93, so as to keep the pressure difference between the first working chamber 203 or the second working chamber 208 and the second pressure compensation chamber 206 constant. Check valves 8 are arranged between the compensation chamber oil outlet chamber 93 and the first pressure compensation chamber 204 and the third pressure compensation chamber 207 respectively to ensure that the hydraulic oil in the compensation chamber oil outlet chamber 93 flows into the first pressure compensation chamber 204 or the third pressure compensation chamber 207 unidirectionally.

[0050] As a preferred embodiment of the commutation union with load holding of the present invention, refer to Figure 4 and Figure 5 , a first overflow valve 6 and a second overflow valve 7 are respectively provided between the first working oil port A and the oil return port T, and between the second working oil port B and the oil return port T. Specifically, the oil inlet of the first overflow valve 6 is communicated with the first working chamber 203, and the oil outlet of the first overflow valve 6 is communicated with the first oil return chamber 202. When the hydraulic oil pressure at the first working oil port A exceeds the set value, it can directly unload to the oil return port T through the first overflow valve 6: Since the first holding valve 3, the second holding valve 4 and the holding pilot valve 5 are arranged in the valve body 1 at the second working oil port B, in order to facilitate the installation of the second overflow valve 7, an overflow oil passage 106 and an overflow oil passage 107 are also provided in the valve body 1. The main valve chamber 22 further includes a third oil return chamber 210 located between the second oil return chamber 209 and the second spring chamber 211. The third oil return chamber 210 is communicated with the oil return port T. The oil inlet of the second overflow valve 7 is communicated with the first holding valve oil outlet chamber 34 through the overflow oil passage 107, and the oil return port of the second overflow valve 7 is communicated with the third oil return chamber 210 through the overflow oil passage 106. When the hydraulic oil pressure at the second working oil port B exceeds the set value, it can directly unload to the oil return port T through the second overflow valve 7 to ensure that the hydraulic actuator works at the set pressure and ensure work safety.

[0051] It should be noted that, for the convenience of repairing the oil passages inside the main valve 2 and the valve body 1, refer to Figure 4 , the valve body 1 adopts a split design, including a main valve body 11, a first end cover 12 and a second end cover 13. The main valve chamber 22 penetrates through the main valve body 11. The first end cover 12 and the second end cover 13 are respectively installed on both sides of the main valve body 11 to seal the two ends of the main valve chamber 22 on the main valve body 11 to form a complete main valve chamber 22. Among them, the first spring chamber 201 is arranged in the first end cover 12, and a first control oil port a is opened on the first end cover 12. The second spring chamber 211 is arranged in the second end cover 13, and a second control oil port b is opened on the second end cover 13.

[0052] The working principle of the commutation union with load holding of the present invention will be described below in combination with relatively preferred embodiments. Among them, the hydraulic actuator is a hydraulic cylinder, the first working oil port A is connected to the rod chamber of the hydraulic cylinder, and the second working oil port B is connected to the rodless chamber of the hydraulic cylinder:

[0053] When there is no control oil input to both the first control oil port a and the second control oil port b, the main spool 21 is in the neutral position, and the oil circuits between the first working oil port A, the second working oil port B, the oil return port T, and the oil inlet port P are all blocked by the seal formed between the main spool 21 and the main valve cavity 22. At the same time, the oil circuit between the oil discharge oil passage 105 of the second holding valve and the oil return port T is also blocked by the seal formed between the main spool 21 and the main valve cavity 22, and the holding pilot valve 5 is in the closed state. Under the action of the oil pressure in the control cavity 45 of the second holding valve and the return spring 42 of the second holding valve, the second holding spool 41 is tightly held against the oil outlet 44 of the second holding valve, forming a conical seal between the oil outlet 44 of the second holding valve and the oil inlet cavity 43 of the second holding valve, blocking the hydraulic oil in the control cavity 35 of the first holding valve from leaking through the control oil passage 102 of the first holding valve and the oil discharge oil passage 105 of the second holding valve from the gap between the main spool 21 and the main valve cavity 22, ensuring that the oil pressure in the oil discharge oil passage 105 of the second holding valve will not decrease, so that under the action of the oil pressure in the control cavity 35 of the first holding valve and the return spring 32 of the first holding valve, the first holding spool 31 can always be tightly held against the oil inlet 33 of the first holding valve, forming a conical seal between the oil inlet 33 of the first holding valve and the oil outlet cavity 34 of the first holding valve, blocking the oil from leaking through the gap between the main spool 21 and the main valve cavity 22 from the second working oil port B, so that the hydraulic cylinders connected to the first working oil port A and the second working oil port B remain stationary at the original position, and their telescopic lengths will not change due to the load. Under the action of the double seal, its load holding function is greatly improved.

[0054] When control oil is input to the first control oil port a, the main spool 21 is in the first working position, the oil inlet cavity 205 is communicated with the second pressure compensation cavity 206, the first pressure compensation cavity 204 is communicated with the first working cavity 203, the second oil return cavity 209 is communicated with the second working cavity 208, and the oil discharge oil passage 105 of the second holding valve is communicated with the second oil return cavity 209. The high-pressure hydraulic oil at the oil inlet port P flows into the compensation valve 9 from the oil inlet cavity 205 and the second pressure compensation cavity 206 in sequence, and after pressure compensation, it flows into the rod chamber from the first pressure compensation cavity 204, the first working cavity 203, and the first working oil port A in sequence; at the same time, the control hydraulic oil at the first control oil port a passes through the first spring cavity 201 and the pilot signal oil passage 101 into the pilot valve signal cavity 52 in sequence, pushing the holding pilot spool 51 to open the flow oil passage between the pilot valve oil inlet cavity 53 and the pilot valve oil discharge cavity 54, and the control cavity 45 of the second holding valve is unloaded through the second holding valve control oil passage 104 to push the second holding spool 41 to open, so that the control cavity 35 of the first holding valve is communicated with the oil return port T to realize unloading, to push the first holding spool 31 to open, and the hydraulic oil in the rodless cavity of the hydraulic cylinder passes through the second working port B and flows through the oil outlet cavity 34 of the first holding valve, the oil outlet of the first holding valve 33, the second working cavity 208, and the second oil return chamber 209 to return oil to the oil return port T in sequence, thereby realizing the retraction of the piston rod of the hydraulic cylinder.

[0055] When the control oil is input from the second control oil port b, the main spool 21 is in the second working position. The oil inlet chamber 205 is communicated with the second pressure compensation chamber 206, the third pressure compensation chamber 207 is communicated with the second working chamber 208, the first oil return chamber 202 is communicated with the first working chamber 203, and the oil path between the second oil return chamber 209 and the oil discharge oil path 105 of the second holding valve is sealed off by the main spool 21 and the main valve chamber 22. The high-pressure hydraulic oil at the oil inlet P flows into the compensation chamber 9 from the oil inlet chamber 205 and the second pressure compensation chamber 206 in sequence. After pressure compensation, it flows through the third pressure compensation chamber 207 and the second working chamber 208 in sequence and flows to the oil inlet 33 of the first holding valve, pushing the first holding valve 31 to make the oil inlet 33 of the first holding valve and the oil outlet chamber 34 of the first holding valve the same, and then flowing to the second working oil port B to supply oil to the rodless chamber; at the same time, the hydraulic oil in the rod chamber of the hydraulic cylinder flows back to the oil return port T through the first working oil port A, the first working chamber 203 and the first oil return chamber 202 in sequence, thereby realizing the extension of the piston rod of the hydraulic cylinder.

[0056] The present invention also provides a hydraulic system, which includes the commutation union with load holding of the present invention. Therefore, this hydraulic system has all the beneficial effects of the commutation union with load holding of the present invention, and will not be elaborated here too much.

[0057] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0058] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any appropriate way without contradiction. To avoid unnecessary repetition, the present invention will not describe various possible combination methods separately.

[0059] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A commutation union with load holding, characterized in that, It includes a valve body (1) provided with an oil inlet (P), an oil return port (T), a first working oil port (A), a second working oil port (B), a first control oil port (a) and a second control oil port (b). Inside the valve body (1), a main valve (2), a first holding valve (3), a second holding valve (4) and a holding pilot valve (5) are arranged. The main valve (2) includes a main spool (21) and a main valve chamber (22). The hydraulic oil through the first control oil port (a) and the second control oil port (b) controls the movement of the main spool (21) in the main valve chamber (22). The movement stroke range of the main spool (21) at least includes a first working position and a second working position for controlling the hydraulic actuator to move in opposite directions to each other, and a neutral position located between the first working position and the second working position. Wherein, when the main spool (21) is in the first working position state, the first working oil port (A) is communicated with the oil inlet (P), and the second working oil port (B) is communicated with the oil return port (T); when the main spool (21) is in the neutral position state, the oil inlet (P), the oil return port (T), the first working oil port (A) and the second working oil port (B) are mutually cut off; when the main spool (21) is in the second working position state, the second working oil port (B) is communicated with the oil inlet (P), and the first working oil port (A) is communicated with the oil return port (T); the first holding valve (3) is located between the second working oil port (B) and the main valve (2) to be able to block the oil circuit between the second working oil port (B) and the main valve (2) when the main spool (21) is in the neutral position state. The second holding valve (4) is arranged on the unloading oil circuit connected to the control end of the first holding valve (3), and the control end of the second holding valve (4) is connected to the holding pilot valve (5) to be able to block the unloading oil circuit connected to the control end of the first holding valve (3) under the control of the holding pilot valve (5); A compensation valve (9) is further arranged inside the valve body (1). The compensation valve (9) is connected to the main valve (2) to control the constant pressure difference before and after the main valve (2); The main valve chamber (22) includes a first spring chamber (201), a first oil return chamber (202), a first working chamber (203), a first pressure compensation chamber (204), an oil inlet chamber (205), a second pressure compensation chamber (206), a third pressure compensation chamber (207), a second working chamber (208), a second oil return chamber (209) and a second spring chamber (211). The first spring chamber (201) is connected to the first control oil port (a), the second spring chamber (211) is connected to the second control oil port (b), both the first oil return chamber (202) and the second oil return chamber (209) are connected to the oil return port (T), the oil inlet chamber (205) is connected to the oil inlet port (P), the first pressure compensation chamber (204), the second pressure compensation chamber (206) and the third pressure compensation chamber (207) are all connected to the compensation valve (9), the first working chamber (203) is connected to the first working oil port (A), and the second working chamber (208) is connected to the first holding valve (3). Among them, when the main valve spool (21) is in the first working position state, the oil inlet chamber (205) communicates with the second pressure compensation chamber (206), the first pressure compensation chamber (204) communicates with the first working chamber (203), and the second oil return chamber (209) communicates with the second working chamber (208) and the second holding valve (4); when the main valve spool (21) is in the second working position state, the oil inlet chamber (205) communicates with the second pressure compensation chamber (206), the third pressure compensation chamber (207) communicates with the second working chamber (208), the oil path between the first oil return chamber (202) and the first working chamber (203) is conducted, and the oil path between the second oil return chamber (209) and the second holding valve (4) is cut off; when the main valve spool (21) is in the middle position state, the oil path between the oil inlet chamber (205) and the second pressure compensation chamber (206) is cut off, the oil paths between the first working chamber (203) and the first oil return chamber (202) and the first pressure compensation chamber (204) are cut off, the second working chamber (208) is not communicated with the third pressure compensation chamber (207) and the second oil return chamber (209), and the oil path between the second oil return chamber (209) and the second holding valve (4) is cut off.

2. The commutation link with load holding according to claim 1, characterized in that, The unloading oil path connected to the control end of the first holding valve (3) is connected to the main valve (2). When the main valve spool (21) is in the first working position state, this unloading oil path communicates with the oil return port (T). When the main valve spool (21) is in the middle position or the second working position state, this unloading oil path is cut off.

3. The reversing union with load holding according to claim 1, characterized in that, The first holding valve (3) includes a first holding valve core (31), a first holding valve return spring (32), a first holding valve oil inlet (33) communicating with the second working chamber (208), a first holding valve oil outlet chamber (34) communicating with the second working oil port (B), and a first holding valve control chamber (35) connected to the second holding valve (4). The first holding valve return spring (32) is disposed within the first holding valve control chamber (35) so as to be able to abut one end of the first holding valve core (31) against the first holding valve oil inlet (33), forming a conical seal between the first holding valve oil inlet (33) and the first holding valve oil outlet chamber (34).

4. The commutation union with load holding according to claim 3, characterized in that The second holding valve (4) includes a second holding valve core (41), a second holding valve return spring (42), a second holding valve oil inlet chamber (43), a second holding valve oil outlet (44), and a second holding valve control chamber (45). The second holding valve return spring (42) is disposed within the second holding valve control chamber (45) so as to be able to abut one end of the second holding valve core (41) against the second holding valve oil outlet (44), forming a conical seal between the second holding valve oil outlet (44) and the second holding valve oil inlet chamber (43). Inside the valve body (1), a first holding valve control oil passage (102), a second holding valve control oil passage (104), and a second holding valve oil drain passage (105) are formed. The first holding valve control oil passage (102) communicates the first holding valve control chamber (35) with the second holding valve oil inlet chamber (43). The second holding valve control oil passage (104) communicates the second holding valve control chamber (4) with the holding pilot valve (5). The second holding valve oil drain passage (105) communicates the second holding valve oil outlet (44) with the main valve chamber (22). Wherein, when the main valve core (21) is in the first working position state, the second holding valve oil drain passage (105) communicates with the second oil return chamber (209). When the main valve core is in the second working position or the neutral position state, the main valve core (21) blocks the connection between the second holding valve oil drain passage (105) and the second oil return chamber (209).

5. The commutating union with load holding according to claim 4, characterized in that, The holding pilot valve (5) includes a holding pilot valve core (51) and a holding pilot valve chamber. The holding pilot valve chamber includes a pilot valve signal oil chamber (52) communicating with the first control oil port (a), a pilot valve oil inlet chamber (53) communicating with the second holding valve control oil passage (104), and a pilot valve oil drain chamber (54) communicating with the oil return port (T). The hydraulic oil at the first control oil port (a) controls the movement of the holding pilot valve core (51) within the holding pilot valve chamber, so that the pilot valve oil inlet chamber (53) communicates with the pilot valve oil drain chamber (54).

6. The commutation union with load holding according to claim 1, characterized in that, A check valve (8) is provided between the compensating valve (9) and the main valve (2).

7. The commutation link with load holding according to any one of claims 1-6, characterized in that, A first overflow valve (6) and a second overflow valve (7) are respectively arranged between the first working oil port (A) and the oil return port (T) and between the second working oil port (B) and the oil return port (T).

8. A hydraulic system, characterized in that, Comprising a commutation union with load holding according to any one of claims 1-7.

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