Reversing valve group and pumping hydraulic system

Abstract

The invention belongs to the field of pumping, and discloses a reversing valve group and a pumping hydraulic system. The reversing valve set comprises a reversing valve and an unloading valve which are integrally arranged, the reversing valve is a sliding valve, and a reversing valve rod is used for controlling the unloading valve to be switched to an unloading closed state at the end stroke position of a valve rod and to be switched to an unloading open state at the midpoint stroke position of the valve rod. According to the reversing valve group and the pumping hydraulic system, the unloading valves are integrated in the reversing valves to form the reversing valve group, opening or closing of the unloading valves is controlled through the stroke of the reversing valve rod, and therefore pressure impact generated in the reversing process can be avoided.

Description

Technical Field

[0001] The present application belongs to the field of pumping, and in particular, relates to a pumping hydraulic system and a reversing valve group used therein. Background Art

[0002] In common pumping hydraulic systems, the reversing valves that control the pumping cylinder groups generally have an M-type neutral position function, meaning that all working oil ports are blocked, but port P is connected to port T, thereby achieving neutral unloading. Alternatively, when using a reversing valve with an O-type neutral position function, since all valve ports are blocked in the neutral position, an additional electromagnetic unloading valve is installed to unload the oil. However, the former reversing valve is prone to unloading, where the high-pressure oil at port P is suddenly released to port T, causing a large pressure shock when the return oil is on and off, and easily damaging the heat dissipation components. The latter reversing valve is prone to the problem of the reversing valve stem not yet shifting into place when the unloading valve is closed. At this time, the closed and blocked port P is prone to pressure shock, causing the engine to slow down or stall. Summary of the Invention

[0003] In response to the above-mentioned defects or shortcomings, the present application discloses a reversing valve group and a pumping hydraulic system to avoid pressure shock during the reversing process.

[0004] To achieve the above-mentioned purpose, the present application discloses a reversing valve group, including an integrated reversing valve and an unloading valve, wherein the reversing valve is a sliding valve and the reversing valve stem is used to control the unloading valve to switch to an unloading closed state at the end stroke position of the valve stem and to switch to an unloading open state at the midpoint stroke position of the valve stem.

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

[0006] The reversing valve body is provided with an axial reversing valve stem cavity and an oil inlet cavity, an oil return cavity and a working oil cavity extending to the reversing valve stem cavity; and

[0007] The reversing valve stem is slidably arranged in the reversing valve stem cavity, and a valve stem inner flow channel is arranged in the reversing valve stem;

[0008] In which, 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 in the valve wall; at the end stroke position of the valve stem, the flow channel in the valve wall connects the flow channel in the valve stem and the oil inlet chamber, and at the midpoint stroke position of the valve stem, the flow channel in the valve wall can connect the oil return chamber.

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

[0010] A conducting groove, used for controlling the working oil chamber to selectively connect with the oil inlet chamber or the oil return chamber;

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

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

[0013] In some embodiments, the flow cross-sectional area of ​​the flow channel in the valve stem and the flow channel in the valve wall is no greater than 1 / 5 of the minimum flow cross-sectional area of ​​the oil inlet cavity or the oil return cavity.

[0014] In some embodiments, the unloading valve is centrally disposed on the reversing valve body and distributed radially, 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 located on axial sides of the oil inlet chamber, and the oil return chamber is located on a first axial side of the oil inlet chamber and is spaced apart from 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 an inner oil return channel. The inner oil return channel extends to the second axial side of the oil inlet chamber and is spaced apart on the axial outside of the second working oil chamber.

[0016] In some embodiments, the valve stem inner flow channel includes a first valve stem inner flow channel and a second valve stem inner flow channel provided at both axial ends of the reversing valve stem; the valve wall inner flow channel includes a first valve wall inner flow channel and a second valve wall inner flow channel extending from the hydraulic control chamber toward both axial ends;

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

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

[0019] The overflow valve is integrated on the valve wall of the reversing valve body, and the valve mouth is arranged between the oil return flow channel and the oil inlet chamber.

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

[0021] The present application also discloses a pumping hydraulic system, comprising a pumping cylinder group and the above-mentioned reversing valve group, wherein the reversing valve is used to control the pumping cylinder group.

[0022] In the reversing valve assembly and pumping hydraulic system of the present application, an unloading valve is integrated into the reversing valve to form the reversing valve assembly, and the stroke of the reversing valve stem is used to control the opening or closing of the unloading valve, thereby avoiding pressure shock. As the reversing valve stem moves to the mid-stroke position of the valve stem, oil gradually returns to the hydraulic control chamber of the unloading valve, causing the unloading valve to gradually switch to the unloading open state. At this time, the high-pressure oil in port P will slowly open the unloading valve, and gradually unload the oil through the unloading valve at a large flow rate. Therefore, the high-pressure oil in port P will not be suddenly released to port T, causing a large pressure shock when the return oil is opened and closed, and damaging the heat dissipation components. As the reversing valve stem moves to the end stroke position of the valve stem, the high-pressure oil in port P can be at least partially unloaded through the unloading valve. Therefore, before the reversing valve switches to the working valve position, the pumped high-pressure oil can be at least partially unloaded through the unloading valve, thereby preventing oil blockage and pressure shock at port P. Moreover, the opening speed of the unloading valve can be further limited by the reversing valve stem, thereby significantly reducing the instantaneous pressure impact of the main pump's high-pressure oil on the T port.

[0023] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide an understanding of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the present application but do not constitute a limitation of the present application. In the accompanying drawings:

[0025] Figure 1 This is a structural schematic diagram of the reversing valve assembly according to a specific embodiment of the present application when the reversing valve stem is in the middle position;

[0026] Figure 2 for Figure 1 A schematic structural diagram of the reversing valve body in the reversing valve group shown;

[0027] Figure 3 for Figure 1 A schematic structural diagram of the reversing valve stem in the reversing valve group shown;

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

[0029] Figure 5 This is a structural 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 It is a hydraulic principle diagram of a pumping hydraulic system according to a specific embodiment of the present application.

[0031] Description of Reference Numerals

[0032] 100 Directional valve 200 Unloading valve

[0033] 300 Relief Valve 1 Reversing Valve Stem

[0034] 2. Directional valve body 3. Directional valve stem cavity

[0035] 11 Conducting slot 12 Gear slot

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

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

[0038] P Oil inlet chamber L Oil return channel

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

[0040] T oil return chamber DETAILED DESCRIPTION

[0041] The following is a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0042] The reversing valve group and the pumping hydraulic system according to the present application will be described below with reference to the accompanying drawings.

[0043] This application discloses a new type of reversing valve group. Figures 1 to 3 In a specific embodiment, the reversing valve group includes an integrated reversing valve 100 and an unloading valve 200. The reversing valve 100 is a sliding valve and the reversing valve stem 1 is used to control the unloading valve 200 to switch to an unloading closed state at the end stroke position of the valve stem and to switch to an unloading open state at the midpoint stroke position of the valve stem.

[0044] The present application aims to integrate the unloading valve 200 into the reversing valve 100, and utilize the stroke of the reversing valve stem 1 to control the opening or closing of the unloading valve 200 to avoid pressure shock. When the reversing valve stem 1 is at the mid-stroke position of the valve stem, the unloading valve 200 is controlled to be in the unloading open state, that is, the hydraulic control chamber of the unloading valve 200 returns oil, and at this time, the high-pressure oil at the P port will be unloaded at a large flow rate through the unloading valve 200. Before the reversing valve stem 1 moves to the working position (for example, the valve stem end stroke position in this embodiment), the high-pressure oil at the P port can be at least partially unloaded through the unloading valve 200, and the high-pressure oil will not cause oil blockage or pressure shock at the P port. Alternatively, when reversing valve stem 1 moves to a position near the midpoint of its travel, unloading valve 200 switches from a closed unloading state to an open unloading state. High-pressure oil at port P is unloaded through unloading valve 200 rather than suddenly released to port T or the oil return channel. Furthermore, because the pressure release in the hydraulic control chamber of unloading valve 200 is gradual, this prevents sudden release of high-pressure oil from port P to port T or the oil return channel. Therefore, limiting the opening speed of the unloading valve by reversing valve stem 1 during pumping reversal significantly reduces the instantaneous pressure shock of the main pump's high-pressure oil on port T, preventing radiator damage and other malfunctions.

[0045] Comparatively, in Chinese patent application CN210461217U, for example, the high-flow spool valve employs an M-type mechanism. In the neutral position, port P connects to port T via the valve stem, achieving neutral unloading. In the reversing position, the valve stem disconnects port P and port T, allowing normal pumping operation. However, when the valve stem utilizes the neutral M-position for unloading, high-pressure oil is suddenly released into the oil return channel, causing a significant pressure surge, which can damage components such as the radiator. In Chinese patent application CN112096683A, for example, the valve stem employs an O-type mechanism, preventing unloading. Therefore, a solenoid unloading valve is added to provide this relief. However, in winter, at low temperatures, the high-flow spool valve's reversing speed slows. Often, after the solenoid unloading valve closes, the high-flow spool valve has not yet fully reversed and remains in the O-type mechanism. During this period, port P becomes a closed chamber, generating a pressure surge. This pressure surge can cause the engine to lose speed or stall. To this end, the power-on closing delay time of the electromagnetic unloading valve can be increased to avoid pressure shock at the pumping oil port of the main pump, but this also reduces the pumping efficiency, and the addition of the electromagnetic unloading valve reduces product reliability.

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

[0047] The reversing valve body 2 is provided with an axial reversing valve stem chamber 3 and an oil inlet chamber P, an oil return chamber T and a working oil chamber extending to the reversing valve stem chamber 3; and

[0048] The reversing valve stem 1 is slidably disposed in the reversing valve stem cavity 3, and a valve stem inner flow channel is disposed in the reversing valve stem 1;

[0049] Among them, 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 (that is, the spring chamber of the unloading valve 200 shown in the figure) extends to the reversing valve stem chamber 3 through the flow channel in the valve wall; at the end stroke position of the valve stem, the flow channel in the valve wall connects the flow channel in the valve stem and the oil inlet chamber P, and at the midpoint stroke position of the valve stem, the flow channel in the valve wall can connect to the oil return chamber T.

[0050] As can be seen, by designing the flow passages within the hydraulic control chamber of unloading valve 200 and the flow passages within the valve stem of reversing valve stem 1, as well as their positional distribution within reversing valve body 2, it is possible to utilize the stroke of reversing valve stem 1 to control the opening or closing of unloading valve 200. That is, unloading valve 200 can be switched to a closed, unloading state at the end of the valve stem stroke and to an open, unloading state at the midpoint of the valve stem stroke. Therefore, compared to using a separate unloading solenoid valve, the unloading solenoid valve can be eliminated, and the opening or closing of the unloading valve can be controlled solely by the reversing valve stem.

[0051] Among them, at the midpoint of the valve stem stroke, in order to enable the flow channel in the valve wall to connect to the oil return chamber T, Figure 3 The reversing valve stem 1 shown may include a gear slot 12, which is used to connect the flow channel in the valve wall to the oil return chamber T at the midpoint of the valve stem stroke. Figure 1 In addition, the reversing valve stem 1 may further include a conducting groove 11, which is used to control the working oil chamber to selectively connect to the oil inlet chamber P or the oil return chamber T, which will be described in detail below.

[0052] See also Figure 1 At this point, the reversing valve stem 1 is at its mid-stroke position. The oil in the hydraulic control chamber of the unloading valve 200 is connected to the return oil flow channel L and the return oil chamber T through the inner flow channel of the valve wall and the gear 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 oil inlet chamber P with the return oil chamber T, thereby directly unloading and returning the oil. This avoids the problem of pressure shock caused by the sudden direct connection between the oil inlet chamber P and the return oil chamber T at the mid-stroke position of the valve stem. In other words, at the mid-stroke position of the valve stem, since the unloading of the unloading valve spring chamber requires time, a delay is also required between ports P and T before unloading can begin, meaning that no pressure shock is generated at port T.

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

[0054] In this embodiment, to achieve high-flow unloading and avoid pressure shock, both the oil inlet chamber P and the oil return chamber T utilize relatively large cross-sectional channels. Furthermore, the flow channels within the valve stem and valve wall are used to build up or release oil pressure in the hydraulic control chamber of the unloading valve 200. Therefore, relatively small cross-sectional channels are employed to provide a time delay or damping effect. For example, the cross-sectional area of ​​each of the flow channels within the valve stem and valve wall should be no greater than 1 / 5 of the minimum cross-sectional area of ​​the oil inlet chamber P or the oil return chamber T.

[0055] On the basis of realizing the above-mentioned reversing and unloading functions, in order to achieve the purpose of simple arrangement of each oil channel and chamber, see Figure 2 On the reversing valve body 2, the unloading valve 200 is centrally arranged 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, which are arranged on both axial sides of the oil inlet chamber P, and the return oil 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; wherein, the return oil chamber T is connected to the valve port end of the reversing valve body 2 through the return oil inner flow channel L, and the return oil inner flow channel L extends to the second axial side of the oil inlet chamber P and is spaced apart on the axial outside of the second working oil chamber A. It can be seen that in this reversing valve 100, when the reversing valve stem 1 moves to the middle position, it is the above-mentioned valve stem midpoint stroke position, and when the reversing valve stem 1 moves to the left end or the 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. Figure 6 , but it is obvious that the reversing valve 100 can have more valve positions and oil ports.

[0056] Specific to Figure 6 The three-position four-way electro-hydraulic directional valve shown in FIG. 1 is used to realize the reversing function of the directional valve 100 and the unloading function of the unloading valve 200. Figure 3 The above-mentioned valve stem inner flow channel may include a first valve stem inner flow channel 13 and a second valve stem inner flow channel 14 provided at both axial ends of the reversing valve stem 1; Figure 2 The valve wall inner flow channel may include a first valve wall inner flow channel 21 and a second valve wall inner flow channel 22 extending from the hydraulic control chamber toward both axial sides; wherein, the axial outer end of the first valve stem inner flow channel 13 is used to connect with the first valve wall inner flow channel 21 and the axial inner end is used to connect with the first working oil chamber B, and the axial outer end of the second valve stem inner flow channel 14 is used to connect with the second valve wall inner flow channel 22 and the axial inner end is used to connect with the second working oil chamber A.

[0057] The left-right symmetrical design of the flow channel inside the valve stem and the flow channel inside the valve wall makes it possible for the hydraulic control chamber of the unloading valve 200 to be connected to the relatively high-pressure oil chambers in the first working oil chamber B and the second working oil chamber A through the flow channel inside the valve wall and the flow channel inside the valve stem in sequence when the reversing valve stem 1 moves to the left-end valve stem end stroke position or the right-end valve stem end stroke position, thereby closing the unloading valve 200.

[0058] For the convenience of processing, any of 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 an axial flow channel and a radial flow channel. 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 viewing angle, only the respective radial flow channels are shown in the form of circles.

[0059] In this embodiment, if Figure 1 The illustrated reversing valve assembly also includes a relief valve 300, integrated into the valve wall of the reversing valve body 2, with its valve opening positioned between the return oil flow channel L and the oil inlet chamber P. The integration of the relief valve 300 enhances the integration of the reversing valve assembly, resulting in a more compact structure and comprehensive functionality. The return oil flow channel L extends to the second axial side of the oil inlet chamber P and is spaced axially outward of the second working oil chamber A. This not only facilitates communication between the hydraulic control chamber of the unloading valve 200 and the return oil chamber T via the shift groove 12, but also facilitates the installation of the relief valve 300.

[0060] In addition, in order to realize large flow rate oil return, the unloading valve 200 adopts the form of a cartridge valve. Figure 6 After adopting the cartridge valve, even when the reversing valve with the O-type center position function is in the center position, the high-pressure oil at the P port can open the cartridge valve in the positive direction, thereby achieving large-flow unloading, and will not cause pressure accumulation or pressure shock to the oil inlet chamber P of the reversing valve.

[0061] Based on the above, this application also discloses a pumping hydraulic system, including a pumping cylinder group and the aforementioned reversing valve group, with reversing valve 100 used to control the pumping cylinder group. The integrated and optimized design of the reversing valve group not only achieves high integration and low cost, but also provides smooth operation, timely unloading during the reversing process, and no pressure shock.

[0062] Specifically, during the pumping reversing process, the reversing valve stem 1 is used to control the opening or closing of the unloading valve 200, thereby avoiding the pressure shock at the P port and significantly reducing the instantaneous pressure shock of the high-pressure oil at the P port on the oil return chamber T. Figure 6 When the reversing valve 100 is in the middle position, the spring chamber of the unloading valve 200 can be connected to the oil return chamber T from both ends through the flow channel in the valve wall and the gear groove 12, so that the unloading valve 200 is opened 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, the reversing valve stem 1 moves from the middle position to the left end until it reaches the bottom. As the valve stem reversing stroke increases, the gear groove 12 at the left end can successively disconnect the connection between the flow channel 22 in the second valve wall and the return oil chamber T, the oil inlet chamber P is connected to the first working oil chamber B, and the second working oil chamber A is connected to the return oil chamber T. The gear groove 12 at the right end disconnects the connection between the flow channel 21 in the first valve wall and the return oil chamber T, the flow channel 13 in the first valve stem is connected to the first working oil chamber B and the flow channel 21 in the first valve wall, the unloading valve 200 is closed, and the main pump pressure oil enters the first working oil chamber B through the oil inlet chamber P, driving the pumping cylinder group to operate.

[0064] like Figure 5 As shown, the reversing valve stem 1 moves from the middle position to the right until it reaches the bottom. As the valve stem reversing stroke increases, the gear groove 12 at the right end disconnects the flow channel 21 in the first valve wall and the return oil chamber T, the oil inlet chamber P is connected to the second working oil chamber A, and the first working oil chamber B is connected to the T chamber. The gear groove 12 at the left end disconnects the flow channel 22 in the second valve wall and the return oil chamber T, the flow channel 14 in the second valve stem is connected to the second working oil chamber A and the flow channel 22 in the second valve wall, the unloading valve 200 is closed, and the main pump pressure oil enters the second working oil chamber A through the oil inlet chamber P, driving the pumping cylinder group to operate.

[0065] It can be seen that the unloading solenoid valve is cancelled in the pumping hydraulic system of the present application, and the opening or closing of the unloading valve 200 is controlled by the reversing valve stem 1 to avoid the pressure shock of the pumping oil port of the main pump during the pumping reversing process. Damping can also be set in the flow channel inside the valve stem of the reversing valve stem 1 to limit the opening speed of the unloading valve 200, which can avoid the pressure oil of the pumping oil port of the main pump from impacting the return oil chamber T, causing the instantaneous pressure of the return oil chamber T to be too high, damaging the radiator and other components. In short, the present application adopts the reversing valve stem 1 to control the opening or closing of the unloading valve 200, which can avoid the pressure shock caused by the pumping oil port of the main pump during the reversing process, and avoid the engine from dropping speed or stalling. During the pumping reversing process, by limiting the opening speed of the unloading valve 200 by the reversing valve stem 1, the instantaneous pressure shock of the high-pressure oil of the main pump on the return oil chamber T can be greatly reduced, avoiding radiator damage and other faults.

[0066] like Figure 6 As shown, the present application also discloses a pumping hydraulic system comprising a pumping cylinder group and the aforementioned reversing valve group, which is used to control the pumping cylinder group. With this highly integrated pumping control valve group, only two basic valve groups are required between the pumping cylinder group and the oil pump or the system's main oil circuit. Furthermore, the system provides comprehensive control functions, smooth control operation, and low cost.

[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 understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0068] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0069] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0070] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. Directional valve group, It is characterized in that The reversing valve group comprises an integrated reversing valve (100) and an unloading valve (200); the reversing valve (100) is a sliding valve; and the reversing valve stem (1) is used to control the unloading valve (200) to switch to an unloading closed state at a valve stem end stroke position and to switch to an unloading open state at a valve stem midpoint stroke position.

2. The reversing valve assembly according to claim 1, It is characterized in that The reversing valve (100) comprises: A reversing valve body (2) is provided with an axially arranged reversing valve stem chamber (3) and an oil inlet chamber (P), an oil return chamber (T) and a working oil chamber extending to the reversing valve stem chamber (3); and The reversing valve stem (1) is slidably arranged in the reversing valve stem cavity (3), and a valve stem inner flow channel is arranged in the reversing valve stem (1); The unloading valve (200) is mounted 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 a flow channel in the valve wall; at the end stroke position of the valve stem, the flow channel in the valve wall connects the flow channel in the valve stem with the oil inlet chamber (P); at the midpoint stroke position of the valve stem, the flow channel in the valve wall can connect the oil return chamber (T).

3. The reversing valve assembly according to claim 2, It is characterized in that The reversing valve stem (1) comprises: A conducting groove (11) for controlling the working oil chamber to selectively connect to the oil inlet chamber (P) or the oil return chamber (T); The gear position groove (12) is used to connect the flow channel in the valve wall to the oil return chamber (T) at the midpoint stroke position of the valve stem.

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

5. The reversing valve assembly according to claim 2, It is characterized in that The flow cross-sectional areas of the flow channel in the valve stem and the flow channel in the valve wall are not greater than 1 / 5 of the minimum flow cross-sectional area of ​​the oil inlet chamber (P) or the oil return chamber (T).

6. The reversing valve assembly according to any one of claims 2 to 5, It is characterized in that On the reversing valve body (2), the unloading valve (200) is centrally arranged and radially distributed, the oil inlet chamber (P) extends to the valve port end of the reversing valve body (2), the working oil chamber comprises a first working oil chamber (B) and a second working oil chamber (A) which are arranged on both axial sides of the oil inlet chamber (P), and the oil return chamber (T) is located on the first axial side of the oil inlet chamber (P) and is arranged at intervals on the axial outer side of the first working oil chamber (B); The oil return chamber (T) is connected to the valve port end of the reversing valve body (2) through an oil return inner flow channel (L), and the oil return inner flow channel (L) extends to the second axial side of the oil inlet chamber (P) and is arranged at an interval on the axial outer side of the second working oil chamber (A).

7. The reversing valve assembly according to claim 6, It is characterized in that The valve stem inner flow channel comprises a first valve stem inner flow channel (13) and a second valve stem inner flow channel (14) arranged at two axial ends of the reversing valve stem (1); the valve wall inner flow channel comprises a first valve wall inner flow channel (21) and a second valve wall inner flow channel (22) extending from the hydraulic control chamber toward two axial ends; The axial outer 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 axial inner end is used to connect to the first working oil chamber (B); the axial outer 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 axial inner end is used to connect to the second working oil chamber (A).

8. The reversing valve assembly according to claim 6, It is characterized in that The reversing valve group comprises: The overflow valve (300) is integrally arranged on the valve wall of the reversing valve body (2), and the valve opening is arranged between the oil return inner flow channel (L) and the oil inlet chamber (P).

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

10. Pumping hydraulic system, including pumping cylinder group, It is characterized in that The pumping hydraulic system further comprises a reversing valve group according to any one of claims 1 to 9, wherein the reversing valve (100) is used to control the pumping cylinder group.

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