Reversing valve group and pumping hydraulic system

Abstract

The application belongs to the field of pumping, and discloses a reversing valve group and a pumping hydraulic system. The reversing valve group comprises a reversing valve and an unloading valve which are arranged integrally, the reversing valve is a spool valve, and a reversing valve rod is used to control the unloading valve to switch to an unloading closed state at an end stroke position of the valve rod and to switch to an unloading open state at a middle stroke position of the valve rod. In the reversing valve group and the pumping hydraulic system, the unloading valve is integrated in the reversing valve to form the reversing valve group, and the stroke of the reversing valve rod is used to control the opening or closing of the unloading valve, so that pressure impact in the reversing process can be avoided.

Description

Technical Field

[0001] This application pertains to the field of pumping, and specifically relates to a pumping hydraulic system and the directional valve assembly used therein. Background Technology

[0002] In common pumping hydraulic systems, the directional valves controlling the pumping cylinder assembly typically have an M-type neutral position function, meaning all working ports are closed, but port P is connected to port T, thus achieving neutral unloading. Alternatively, when using a directional valve with an O-type neutral position function, since all ports are closed in the neutral position, an additional solenoid unloading valve is installed for unloading. However, the former directional valve is prone to issues where, during unloading, high-pressure oil at port P is suddenly released to port T, causing a large pressure surge during return oil switching, which can easily damage cooling components. The latter directional valve is prone to issues where, when the unloading valve closes, the directional valve stem has not yet switched to the correct position; in this closed state, port P is prone to pressure surges, leading to engine speed drops or stalling. Summary of the Invention

[0003] To address the aforementioned defects or deficiencies, this application discloses a directional valve assembly and a pumping hydraulic system to avoid pressure shocks during the directional switching process.

[0004] To achieve the above objectives, this application discloses a reversing valve assembly, including an integrated reversing valve and an unloading valve. The reversing valve is a spool valve, and the reversing valve stem is used to control the unloading valve to switch to an unloading closed state at the end of the stem stroke position and to switch to an unloading open state at the midpoint of the stem stroke position.

[0005] In some embodiments, the reversing valve includes:

[0006] The directional valve body includes an axially oriented directional valve stem cavity and an inlet cavity, a return cavity, and a working cavity extending into the directional valve stem cavity; and

[0007] The reversing valve stem is slidably disposed in the reversing valve stem cavity, and an internal flow channel is provided inside the reversing valve stem;

[0008] The unloading valve is installed on the valve wall of the reversing valve body, and the hydraulic control chamber of the unloading valve extends to the reversing valve stem chamber through the flow channel inside the valve wall. At the end of the valve stem, the flow channel inside the valve wall connects the flow channel inside the valve stem with the oil inlet chamber. At the midpoint of the valve stem, the flow channel inside the valve wall connects to the oil return chamber.

[0009] In some embodiments, the reversing valve stem includes:

[0010] The guide groove is used to control the working oil chamber to selectively connect to the oil inlet chamber or the oil return chamber;

[0011] The gear slot is used to connect the flow channel inside the valve wall to the oil return chamber at the midpoint of the valve stem stroke position.

[0012] In some embodiments, the directional valve is a three-position four-way valve with an O-type neutral position function.

[0013] In some embodiments, the cross-sectional area of ​​the flow channel in the valve stem and the flow channel in the valve wall is not greater than 1 / 5 of the minimum cross-sectional area of ​​the oil inlet chamber or the oil return chamber.

[0014] In some embodiments, the unloading valve is centrally located and radially distributed on the reversing valve body, the oil inlet chamber extends to the valve port end of the reversing valve body, the working oil chamber includes a first working oil chamber and a second working oil chamber arranged on both axial sides of the oil inlet chamber, and the oil return chamber is located on the first axial side of the oil inlet chamber and spaced apart on the axial outside of the first working oil chamber.

[0015] The oil return chamber is connected to the valve port end of the reversing valve body through the oil return inner flow channel, and the oil return inner flow channel extends to the second axial side of the oil inlet chamber and is spaced apart on the axial outer side of the second working oil chamber.

[0016] In some embodiments, the valve stem internal flow passage includes a first valve stem internal flow passage and a second valve stem internal flow passage disposed at both axial ends of the reversing valve stem; the valve wall internal flow passage includes a first valve wall internal flow passage and a second valve wall internal flow passage extending from the hydraulic control chamber toward both axial sides.

[0017] Wherein, the outer axial end of the inner flow channel of the first valve stem is used to connect to the inner flow channel of the first valve wall and the inner axial end is used to connect to the first working oil chamber, and the outer axial end of the inner flow channel of the second valve stem is used to connect to the inner flow channel of the second valve wall and the inner axial end is used to connect to the second working oil chamber.

[0018] In some embodiments, the reversing valve assembly includes:

[0019] An overflow valve is integrated on the valve wall of the reversing valve body, with its valve port located between the return oil inner flow channel and the inlet oil chamber.

[0020] In some embodiments, the unloading valve is a cartridge valve.

[0021] This application also discloses a pumping hydraulic system, including a pumping cylinder assembly and the aforementioned reversing valve assembly, wherein the reversing valve is used to control the pumping cylinder assembly.

[0022] In the directional valve assembly and pumping hydraulic system of this application, the unloading valve is integrated into the directional valve to form a directional valve assembly. The opening or closing of the unloading valve is controlled by the stroke of the directional valve stem, thereby avoiding pressure shock. During the movement of the directional valve stem to the midpoint of its stroke, the hydraulic control chamber of the unloading valve gradually returns oil, causing the unloading valve to gradually switch to the unloading open state. At this time, the high-pressure oil at port P will slowly open the unloading valve, gradually unloading at a large flow rate. This prevents the high-pressure oil at port P from suddenly being released to port T, causing a large pressure shock during oil return and making heat dissipation components susceptible to damage. During the movement of the directional valve stem to the end of its stroke, the high-pressure oil at port P can be at least partially unloaded by the unloading valve. Therefore, before the directional valve switches to the working position, the pumped high-pressure oil can be at least partially unloaded by the unloading valve, thus preventing oil blockage and pressure shock at port P. Furthermore, the opening speed of the unloading valve can be limited by the reversing valve stem, which can significantly reduce the instantaneous pressure impact of the main pump high-pressure oil on the T port.

[0023] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0024] The accompanying drawings are provided to illustrate the present application and form part of the specification. They are used together with the following detailed description to explain the present application, but do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a schematic diagram of the reversing valve stem of the reversing valve assembly according to a specific embodiment of this application when the reversing valve stem is in the neutral position.

[0026] Figure 2 for Figure 1 A schematic diagram of the reversing valve body in the reversing valve assembly is shown.

[0027] Figure 3 for Figure 1 A schematic diagram of the reversing valve stem in the reversing valve assembly is shown.

[0028] Figure 4 This is a schematic diagram of the reversing valve stem of the reversing valve assembly according to a specific embodiment of this application when the reversing valve stem is in the left position;

[0029] Figure 5 This is a schematic diagram of the reversing valve assembly according to a specific embodiment of the present application when the reversing valve stem is in the right position;

[0030] Figure 6 This is a hydraulic schematic diagram of a pumping hydraulic system according to a specific embodiment of this application.

[0031] Explanation of reference numerals in the attached figures

[0032] 100 Reversing valve 200 Unloading valve

[0033] 300 Relief Valve 1 Reversing Valve Stem

[0034] 2. Reversing valve body; 3. Reversing valve stem chamber

[0035] 11. Conductor groove; 12. Gear slot

[0036] 13 First valve stem internal flow channel 14 Second valve stem internal flow channel

[0037] 21 First valve wall internal flow channel 22 Second valve wall internal flow channel

[0038] P Inlet oil chamber L Return oil inner flow channel

[0039] A. Second working oil chamber B. First working oil chamber

[0040] T return oil chamber Detailed Implementation

[0041] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this application.

[0042] The following description, with reference to the accompanying drawings, describes the directional valve assembly and pumping hydraulic system according to this application.

[0043] This application discloses a novel directional valve assembly. See also: Figures 1 to 3 In one specific embodiment, the reversing valve group includes an integrated reversing valve 100 and an unloading valve 200. The reversing valve 100 is a spool valve and the reversing valve stem 1 is used to control the unloading valve 200 to switch to the unloading closed state at the end of the stem stroke position and to switch to the unloading open state at the midpoint of the stem stroke position.

[0044] This application aims to integrate the unloading valve 200 into the directional valve 100, using the stroke of the directional valve stem 1 to control the opening or closing of the unloading valve 200, thereby avoiding pressure surges. When the directional valve stem 1 is at the midpoint of its stroke, the unloading valve 200 is controlled to be in the unloading open state, i.e., the hydraulic control chamber of the unloading valve 200 returns oil. At this time, the high-pressure oil at port P will be unloaded at a large flow rate through the unloading valve 200. Before the directional valve stem 1 moves to the working position (e.g., the end stroke position of the valve stem in this embodiment), the high-pressure oil at port P can be at least partially unloaded through the unloading valve 200, and the high-pressure oil will not cause oil blockage or pressure surges at port P. Alternatively, when the directional valve stem 1 moves to a position near the midpoint of its stroke, the unloading valve 200 switches from the unloading closed state to the unloading open state. The high-pressure oil at port P will be unloaded through the unloading valve 200, rather than being suddenly released to port T or the return oil passage. Furthermore, because the pressure release in the hydraulic control chamber of the unloading valve 200 is gradual, it will not cause a sudden release of high-pressure oil from port P to port T or the return oil passage. Therefore, during pump reversal, limiting the opening speed of the unloading valve by the directional valve stem 1 can significantly reduce the instantaneous pressure impact of the main pump's high-pressure oil on port T, preventing radiator damage and other malfunctions.

[0045] Comparatively, in Chinese patent application CN210461217U, the high-flow spool valve uses an M-type function. In the neutral position, port P is connected to port T via the valve stem, achieving neutral unloading. In the reversing position, the valve stem disconnects port P from port T, allowing normal pumping operation. However, using the valve stem's neutral M-type unloading function results in a sudden release of high-pressure oil into the return oil channel, causing a large pressure surge that can easily damage components such as the radiator. In Chinese patent application CN112096683A, for example, the valve stem uses an O-type function, which cannot unload, so a solenoid unloading valve is added. However, in low temperatures during winter, the reversing of the high-flow spool valve slows down. Often, after the solenoid unloading valve closes, the high-flow spool valve has not yet reversed to its correct position and remains in the O-type function position. At this time, port P is a closed cavity, generating a pressure surge. This pressure surge at port P can cause the engine to slow down or stall. To address this, the energization and closure delay time of the electromagnetic unloading valve can be increased to avoid pressure surges at the pumping port of the main pump. However, this also reduces pumping efficiency and lowers product reliability due to the addition of the electromagnetic unloading valve.

[0046] To achieve the integration of the directional control valve and the unloading valve and to avoid oil shock, as an example, the directional control valve 100 of this embodiment may include:

[0047] The directional valve body 2 includes an axially oriented directional valve stem cavity 3, and an inlet cavity P, a return cavity T, and a working cavity extending to the directional valve stem cavity 3; and

[0048] The reversing valve stem 1 is slidably disposed in the reversing valve stem cavity 3, and an internal flow channel is provided inside the reversing valve stem 1;

[0049] The unloading valve 200 is installed on the valve wall of the reversing valve body 2. The hydraulic control chamber of the unloading valve 200 (i.e., the spring chamber of the unloading valve 200 shown in the figure) extends to the reversing valve stem chamber 3 through the flow channel inside the valve wall. At the end of the valve stem, the flow channel inside the valve wall connects the flow channel inside the valve stem with the oil inlet chamber P. At the midpoint of the valve stem, the flow channel inside the valve wall can connect to the return oil chamber T.

[0050] As can be seen, by configuring the flow channels within the valve wall of the hydraulic control chamber of the unloading valve 200, the flow channels within the valve stem of the reversing valve stem 1, and their positions within the reversing valve body 2, the stroke of the reversing valve stem 1 can be used to control the opening or closing of the unloading valve 200. Specifically, the unloading valve 200 can switch to an unloading closed state at the end of the valve stem's stroke and to an unloading open state at the midpoint of the valve stem's stroke. Therefore, compared to using a separate unloading solenoid valve, the unloading solenoid valve can be eliminated, and the unloading valve can be opened or closed simply by controlling it through the reversing valve stem.

[0051] Specifically, at the midpoint of the valve stem's stroke position, to ensure that the flow channel within the valve wall can connect to the return oil chamber T, Figure 3 The directional valve stem 1 shown may include a stop groove 12, which is used to connect the flow channel inside the valve wall to the return oil chamber T when the valve stem is in the midpoint of its stroke position. Figure 1 As shown. In addition, the reversing valve stem 1 may also include a guide groove 11, which is used to control the selective connection of the working oil chamber to the inlet oil chamber P or the return oil chamber T, as will be described in detail below.

[0052] See Figure 1 At this point, the directional valve stem 1 is in the midpoint of its stroke. The oil in the hydraulic control chamber of the unloading valve 200 connects to the return oil flow channel L and the return oil chamber T through the internal flow channel of the valve wall and the stop groove 12. As the pressure in the hydraulic control chamber gradually decreases, the pressure oil at port P gradually opens the valve port of the unloading valve 200, connecting the inlet chamber P and the return oil chamber T, thus directly unloading and returning the oil. This avoids the problem of pressure shock caused by the abrupt direct connection between the inlet chamber P and the return oil chamber T at the midpoint of the valve stem stroke. In other words, at the midpoint of the valve stem stroke, because the unloading of the unloading valve spring chamber requires time, there is also a delay between ports P and T before unloading can begin, meaning that there will be no pressure shock at port T.

[0053] Since the pressure oil at port P will be unloaded and returned by opening the unloading valve 200 at the midpoint of the valve stem stroke position, the directional valve 100 itself can be a three-position four-way valve with O-type neutral position function. The three-position four-way valve with O-type neutral position function is more conventional, with simple structure and low cost.

[0054] In this embodiment, to achieve high-flow unloading and avoid pressure shock, both the inlet chamber P and the return chamber T employ relatively large cross-sectional channels. Meanwhile, the valve stem inner flow channel and the valve wall inner flow channel are used for establishing or releasing oil pressure in the hydraulic control chamber of the unloading valve 200; therefore, they employ relatively small cross-sectional channels to provide delay or damping effects. As an example, the flow cross-sectional area of ​​both the valve stem inner flow channel and the valve wall inner flow channel should not exceed 1 / 5 of the minimum flow cross-sectional area of ​​the inlet chamber P or the return chamber T.

[0055] Based on achieving the aforementioned reversing and unloading functions, and to achieve a simplified layout of the oil passages and chambers, see [reference needed]. Figure 2 On the reversing valve body 2, the unloading valve 200 is centrally located and radially distributed. The inlet chamber P extends to the valve port end of the reversing valve body 2. The working oil chambers include a first working oil chamber B and a second working oil chamber A located on both axial sides of the inlet chamber P. The return oil chamber T is located on the first axial side of the inlet chamber P and is spaced apart on the axial outer side of the first working oil chamber B. The return oil chamber T is connected to the valve port end of the reversing valve body 2 through a return oil internal flow channel L, which extends to the second axial side of the inlet chamber P and is spaced apart on the axial outer side of the second working oil chamber A. Therefore, in this reversing valve 100, when the reversing valve stem 1 moves to the neutral position, it is the aforementioned valve stem midpoint stroke position; when the reversing valve stem 1 moves to the left or right end, it is the working valve position or the valve stem end stroke position. Of course, this is only an example. Figures 1 to 3 The directional control valve 100 shown is a three-position four-way electro-hydraulic directional control valve. See [link / reference]. Figure 6 The schematic diagram is shown, but obviously the directional valve 100 can have more valve positions and oil ports.

[0056] Specifically Figure 6 The three-position four-way electro-hydraulic directional valve shown is used to realize the directional switching function of the directional valve 100 and its unloading function in conjunction with the unloading valve 200. (See [reference needed]). Figure 3 The aforementioned valve stem internal flow channel may include a first valve stem internal flow channel 13 and a second valve stem internal flow channel 14 disposed at both axial ends of the reversing valve stem 1; see also Figure 2 The valve wall internal flow channel may include a first valve wall internal flow channel 21 and a second valve wall internal flow channel 22 extending from the hydraulic control chamber toward both axial sides; wherein, the outer axial end of the first valve stem internal flow channel 13 is used to connect to the first valve wall internal flow channel 21 and the inner axial end is used to connect to the first working oil chamber B, and the outer axial end of the second valve stem internal flow channel 14 is used to connect to the second valve wall internal flow channel 22 and the inner axial end is used to connect to the second working oil chamber A.

[0057] The symmetrical design of the valve stem inner flow channel and the valve wall inner flow channel facilitates the connection between the hydraulic control chamber of the unloading valve 200 and the relatively high-pressure oil chambers in the first working oil chamber B and the second working oil chamber A through the valve wall inner flow channel and the valve stem inner flow channel when the reversing valve stem 1 moves to the left end of the valve stem stroke position or the right end of the valve stem stroke position, thereby closing the unloading valve 200.

[0058] For ease of manufacturing, each of the following flow channels—the first valve stem inner flow channel 13, the second valve stem inner flow channel 14, the first valve wall inner flow channel 21, and the second valve wall inner flow channel 22—includes both axial and radial flow channels. It should be noted that... Figure 3 In the first valve stem inner flow channel 13 and the second valve stem inner flow channel 14 shown, due to the sectional view angle, their respective radial flow channels are only shown in the form of circles.

[0059] In this embodiment, such as Figure 1 The directional valve assembly shown may also include a relief valve 300, which is integrated into the valve wall of the directional valve body 2 and has its valve port located between the return oil inner flow channel L and the inlet oil chamber P. With the relief valve 300 integrated, the directional valve assembly has a higher degree of integration, a more compact structure, and more comprehensive functions. The return oil inner flow channel L extends to the second axial side of the inlet oil chamber P and is spaced apart on the axial outer side of the second working oil chamber A. This not only facilitates the connection of the hydraulic control chamber of the unloading valve 200 to the return oil chamber T via the gear slot 12, but also facilitates the installation of the relief valve 300.

[0060] In addition, to facilitate high-flow-rate oil return, the unloading valve 200 adopts a cartridge valve form. See also Figure 6 With the adoption of cartridge valves, even when the O-type neutral position directional valve is in the neutral position, the high-pressure oil at port P can open the cartridge valve in the forward direction, thereby achieving large-flow unloading without causing pressure accumulation or pressure shock to the oil inlet chamber P of the directional valve.

[0061] Based on the above, this application also discloses a pumping hydraulic system, including a pumping cylinder assembly and the aforementioned directional valve assembly, wherein the directional valve 100 is used to control the pumping cylinder assembly. Through the integrated and optimized design of the aforementioned directional valve assembly, not only is the integration high and the cost low, but it also operates smoothly, and the unloading during the directional switching process is timely, without causing pressure shock.

[0062] Specifically, during the pumping reversing process, the reversing valve stem 1 controls the opening or closing of the unloading valve 200, which avoids the pressure surge at port P and significantly reduces the instantaneous pressure surge of high-pressure oil at port P on the return oil chamber T. See also Figure 6 When the reversing valve 100 is in the neutral position, the spring chamber of the unloading valve 200 can be connected to the return oil chamber T from both ends through the flow channel inside the valve wall and the stop groove 12, so that the unloading valve 200 opens under the action of the pressure oil in the oil inlet chamber P, and the pumping port of the main pump is unloaded.

[0063] like Figure 4 As shown, during the movement of the reversing valve stem 1 from the middle position to the left, as the reversing stroke of the valve stem increases, the left-end shift groove 12 disconnects the connection between the second valve wall inner flow channel 22 and the return oil chamber T, the inlet oil chamber P connects to the first working oil chamber B, the second working oil chamber A connects to the return oil chamber T, the right-end shift groove 12 disconnects the connection between the first valve wall inner flow channel 21 and the return oil chamber T, the first valve stem inner flow channel 13 connects the first working oil chamber B and the first valve wall inner flow channel 21, the unloading valve 200 closes, and the main pump pressure oil enters the first working oil chamber B through the inlet oil chamber P, driving the pumping cylinder group to operate.

[0064] like Figure 5 As shown, during the process of the reversing valve stem 1 moving from the middle position to the right until it reaches the bottom, as the reversing stroke of the valve stem increases, the right end of the shift groove 12 disconnects the first valve wall inner flow channel 21 from the return oil chamber T, the inlet oil chamber P connects to the second working oil chamber A, and the first working oil chamber B connects to the T chamber. The left end of the shift groove 12 disconnects the second valve wall inner flow channel 22 from the return oil chamber T, the second valve stem inner flow channel 14 connects the second working oil chamber A with the second valve wall inner flow channel 22, the unloading valve 200 closes, and the main pump pressure oil enters the second working oil chamber A through the inlet oil chamber P, driving the pumping cylinder group to operate.

[0065] As can be seen, the unloading solenoid valve is eliminated in the pumping hydraulic system of this application. The opening and closing of the unloading valve 200 is controlled by the reversing valve stem 1, avoiding pressure shocks at the pumping port of the main pump during pumping reversal. Furthermore, damping can be installed in the flow channel within the valve stem of the reversing valve stem 1 to limit the opening speed of the unloading valve 200, preventing pressure oil from the pumping port of the main pump from impacting the return oil chamber T, which could cause excessively high instantaneous pressure in the return oil chamber T and damage components such as the radiator. In summary, this application uses the reversing valve stem 1 to control the opening and closing of the unloading valve 200, avoiding pressure shocks from the pumping port of the main pump during reversal, preventing engine speed drops or stalling. During pumping reversal, limiting the opening speed of the unloading valve 200 by the reversing valve stem 1 significantly reduces the instantaneous pressure shock of the high-pressure oil from the main pump on the return oil chamber T, preventing radiator damage and other malfunctions.

[0066] like Figure 6 As shown, this application also discloses a pumping hydraulic system, including a pumping cylinder assembly and the aforementioned directional valve assembly, wherein the directional valve is used to control the pumping cylinder assembly. By employing this highly integrated pumping control valve assembly, only two basic valve assemblies are required between the pumping cylinder assembly and the oil pump or the main oil circuit of the system. Furthermore, the control function is comprehensive, the control operation is smooth, and the cost is low.

[0067] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A reversing valve assembly, characterized in that, The reversing valve group includes an integrated reversing valve (100) and an unloading valve (200). The reversing valve (100) is a spool valve and the reversing valve stem (1) is used to control the unloading valve (200) to switch to the unloading closed state at the end of the stem stroke position and to switch to the unloading open state at the midpoint of the stem stroke position. The reversing valve (100) includes: The reversing valve body (2) includes an axially oriented reversing valve stem cavity (3) and an inlet oil cavity (P), a return oil cavity (T), and a working oil cavity extending to the reversing valve stem cavity (3); and The reversing valve stem (1) is slidably disposed in the reversing valve stem cavity (3), and an internal flow channel is provided inside the reversing valve stem (1); The unloading valve (200) is installed on the valve wall of the reversing valve body (2), and the hydraulic control chamber of the unloading valve (200) extends to the reversing valve stem chamber (3) through the flow channel inside the valve wall. At the end of the valve stem, the flow channel inside the valve wall connects the flow channel inside the valve stem with the oil inlet chamber (P). At the midpoint of the valve stem, the flow channel inside the valve wall connects to the oil return chamber (T). The reversing valve stem (1) includes: The guide groove (11) is used to control the working oil chamber to selectively connect to the oil inlet chamber (P) or the oil return chamber (T). The gear slot (12) is used to connect the flow channel inside the valve wall to the oil return chamber (T) at the midpoint stroke position of the valve stem. The pressure release of the hydraulic control chamber of the unloading valve (200) is gradual. When the reversing valve stem (1) moves to a position close to the midpoint of the valve stem stroke, the unloading valve (200) will switch from the unloading closed state to the unloading open state.

2. The reversing valve assembly according to claim 1, characterized in that, The reversing valve (100) is a three-position four-way valve with O-type neutral position function.

3. The reversing valve assembly according to claim 1, characterized in that, The cross-sectional area of ​​the flow channel in the valve stem and the flow channel in the valve wall is not greater than 1 / 5 of the minimum cross-sectional area of ​​the oil inlet chamber (P) or the oil return chamber (T).

4. The reversing valve assembly according to any one of claims 1 to 3, characterized in that, On the reversing valve body (2), the unloading valve (200) is centrally located and radially distributed. The oil inlet chamber (P) extends to the valve port end of the reversing valve body (2). The working oil chamber includes a first working oil chamber (B) and a second working oil chamber (A) located on both axial sides of the oil inlet chamber (P). The oil return chamber (T) is located on the first axial side of the oil inlet chamber (P) and is spaced apart on the axial outside of the first working oil chamber (B). The oil return chamber (T) is connected to the valve port of the reversing valve body (2) through the oil return inner flow channel (L). The oil return inner flow channel (L) extends to the second axial side of the oil inlet chamber (P) and is spaced apart on the axial outer side of the second working oil chamber (A).

5. The reversing valve assembly according to claim 4, characterized in that, The valve stem internal flow channel includes a first valve stem internal flow channel (13) and a second valve stem internal flow channel (14) disposed at both axial ends of the reversing valve stem (1); the valve wall internal flow channel includes a first valve wall internal flow channel (21) and a second valve wall internal flow channel (22) extending from the hydraulic control chamber toward both axial sides. Wherein, the outer axial end of the first valve stem inner flow channel (13) is used to connect to the first valve wall inner flow channel (21) and the inner axial end is used to connect to the first working oil chamber (B), the outer axial end of the second valve stem inner flow channel (14) is used to connect to the second valve wall inner flow channel (22) and the inner axial end is used to connect to the second working oil chamber (A).

6. The reversing valve assembly according to claim 4, characterized in that, The reversing valve assembly includes: An overflow valve (300) is integrated on the valve wall of the reversing valve body (2) and its valve port is located between the return oil inner flow channel (L) and the oil inlet chamber (P).

7. The reversing valve assembly according to claim 1, characterized in that, The unloading valve (200) is a cartridge valve.

8. A pumping hydraulic system, including a pumping cylinder assembly, characterized in that, The pumping hydraulic system further includes a reversing valve assembly according to any one of claims 1 to 7, wherein the reversing valve (100) is used to control the pumping cylinder assembly.

Images