Five-position eight-way electromagnetic directional valve

Abstract

The invention is suitable for the field of hydraulic control elements, and provides a five-position eight-way electromagnetic reversing valve which comprises a valve body assembly, a double-valve-element cooperative structure and an electromagnetic driving and resetting mechanism, the valve body assembly is cast through a high-strength material, and a first oil inlet P1 and a second oil return opening T2 are formed in the upper portion of the valve body assembly; a second oil inlet P2 and a first oil return port T1 are formed in the right side of the valve body assembly, and two pairs of oil outlets (A1 / B1 and A2 / B2) are symmetrically distributed on the left side and the right side of the valve body assembly; an axially-through main cavity and a plurality of radial oil guide holes are formed in the valve body assembly, an annular oil groove is precisely machined in the inner wall of the main cavity, the radial oil guide holes are ingeniously communicated with an external oil port, and a foundation is laid for precise distribution of oil liquid. According to the invention, the space utilization is optimized, the reversing stability is improved, the control logic is simplified, the leakage control is excellent, and the response speed is accelerated.

Description

Technical Field

[0001] The present invention belongs to the field of hydraulic control components, and particularly relates to a five-position eight-way electromagnetic directional valve. Background Art

[0002] In the field of hydraulic transmission and control, most traditional electromagnetic directional valves adopt a single spool structure, and their working principle is to realize the switching of oil circuits through the displacement of a single spool. However, this structure has many limitations. The number of ports and the combination of positions are restricted by the spool length and shoulder layout, making it difficult to balance the structural compactness when pursuing multi-channel independent control. Under high-pressure and large-flow conditions, the single spool scheme is more prone to hydrodynamic interference, which in turn leads to commutation jamming, seriously affecting the stability and reliability of the system. In addition, when multi-gear switching is required, it is often necessary to rely on multi-valve series connection or complex logic control methods, which not only result in a large volume of equipment, an increase in leakage points, but also cause a series of problems such as response lag.

[0003] From the perspective of theoretical research, the literature (Liu et al., Journal of Dynamic Systems, Measurement, and Control, 2019) clearly points out that the theoretically maximum number of ports of a single spool four-way valve is only 6 (P, T, A, B, and two load-sensitive ports). If the number of ports is to be extended to eight ports, the axial length of the spool needs to be increased significantly to more than 1.5 times that of the conventional design, which will inevitably lead to a significant increase in the volume of the valve body (volume increase ≥ 40%). Moreover, the too-long spool is extremely prone to eccentric wear and jamming problems due to uneven hydrodynamic force distribution (specifically, refer to the test specifications for spool clamping force in GB / T 15623-2022); In terms of improvement schemes, some technologies attempt to adopt a combination of multi-valve parallel or series connection. For example, the double spool parallel structure proposed in patent CN108895044A can achieve eight-port switching, but it brings new problems. This scheme requires an additional inter-valve connection oil circuit, which directly leads to a significant increase in the leakage path (the number of leakage points increases by more than 50%). Under high-pressure (≥ 25 MPa) conditions, the inter-valve coupling vibration will further increase the risk of seal failure (as mentioned in the literature Zhang et al., Tribology International, 2021). In addition, the control logic of the multi-valve system becomes extremely complex, and multiple independent electromagnetic drive units need to be configured, which not only greatly increases the system cost but also significantly increases the failure rate; Therefore, a five-position eight-way electromagnetic directional valve is needed to solve the above problems. Summary of the Invention

[0004] The purpose of the embodiment of the present invention is to provide a five-position eight-way electromagnetic directional control valve to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A five-position eight-way electromagnetic directional control valve, comprising a valve body assembly, a double spool cooperative structure, and an electromagnetic drive and reset mechanism, characterized in that: the valve body assembly is cast with high-strength materials, a first oil inlet P1 and a second oil return port T2 are provided above the valve body assembly, a second oil inlet P2 and a first oil return port T1 are provided below the valve body assembly, and two pairs of oil outlets (A1 / B1, A2 / B2) are symmetrically distributed on the left and right sides of the valve body assembly; an axially penetrating main cavity and several radial oil guide holes are provided inside the valve body assembly, an annular oil groove is precisely machined on the inner wall of the main cavity, and the radial oil guide holes are ingeniously connected to the external oil ports, laying a foundation for the precise distribution of oil; The double spool cooperative structure is composed of a large spool and a small spool nested coaxially; the large spool is a carefully designed stepped shaft structure, a main oil passage axially penetrating is provided inside the large spool, and three shoulders are precisely machined on the outer surface of the large spool; the small spool is connected to the large spool through an axial sliding key, the sliding key precisely limits the displacement range of the small spool relative to the large spool, and a radial oil through hole is provided at the front end of the small spool and communicated with the main oil passage to achieve the cooperative control of the oil circuit; The electromagnetic drive and reset mechanism includes two groups of first proportional electromagnets and second proportional electromagnets with excellent performance, and a large spool return spring and a small spool return spring adapted thereto. The first proportional electromagnet and the second proportional electromagnet drive the large spool and the small spool to be connected through a first push rod and a second push rod respectively. The large spool return spring and the small spool return spring are respectively installed at the ends of the large spool and the small spool to ensure that the large spool and the small spool can be reset after power-off.

[0006] In a further technical solution, the axial strokes of the large spool and the small spool are precisely designed to satisfy the following relationship: the maximum displacement stroke L1 of the large spool = 5 ± 0.1 mm, and the maximum relative displacement stroke L2 of the small spool = 1.2 ± 0.05 mm; the keyway length of the sliding key is precisely designed to be L2, which precisely limits the displacement range of the small spool and ensures the accuracy of the spool movement.

[0007] In a further technical solution, the widths of the variable cross-section shoulders of the large spool are optimized and designed to be 2.4 mm, 1.6 mm, and 2.4 mm respectively, which are perfectly adapted to the oil passages of the valve body to achieve the high efficiency of oil circuit switching.

[0008] In a further technical solution, the stiffness k1 of the large spool return spring = 80 - 90 N / mm, and the pre-tightening force F1 = 100 - 130 N; the stiffness k2 of the small spool return spring = 50 - 60 N / mm, and the pre-tightening force F2 = 70 - 90 N, ensuring the stability and reliability of the spool reset.

[0009] Further technical solution: The driving force range of the first proportional electromagnet and the second proportional electromagnet is 0 - 220 N, and the response time is extremely short, ≤5 ms. High-performance antifriction coatings are provided on the contact surfaces between the first push rod and the end face of the large spool valve and between the second push rod and the end face of the small spool valve. The coating material is molybdenum disulfide (MoS2) or polytetrafluoroethylene (PTFE), which reduces friction and improves the driving efficiency.

[0010] Further technical solution: The first proportional electromagnets and the second proportional electromagnets at both left and right ends each have four gears. Through different gear combinations, diversified oil circuit control logics can be achieved.

[0011] Further technical solution: High-quality sealing rings are provided at the slip key joints. The sealing ring material is filled polytetrafluoroethylene, which has a wide operating temperature range of -40°C to +150°C and can withstand a pressure of ≥35 MPa, effectively preventing oil leakage and improving the sealing performance.

[0012] Further technical solution: The inner wall of the main cavity is specially treated with a uniformly plated hard chromium layer with a thickness of 15 - 25 μm and a surface roughness Ra ≤ 0.2 μm; the surfaces of the large spool valve and the small spool valve are nitrided, with a nitrided layer depth of ≥0.25 mm and a hardness of ≥HRC58, enhancing the wear resistance and corrosion resistance of the valve body and the spool valve.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, the space utilization is optimized: The present invention adopts an innovative double spool valve nested structure, which effectively reduces the axial space occupation compared with the traditional single spool valve structure; by reasonably arranging the valve body oil ports and the spool valve structure, while realizing the eight-port function, the problem of a significant increase in the valve body volume caused by the increase in ports is ingeniously avoided, significantly improving the space efficiency and providing strong support for the compact design of the equipment; In the present invention, the commutation stability is improved: The unique double spool valve design is combined with an electromagnetic-spring redundant drive mechanism; the electromagnet and the return spring form a force closed-loop, providing an adaptive buffering function during the commutation process. When the electromagnet drives the spool valve to move, the return spring can dynamically adjust the movement of the spool valve, effectively suppressing the risks of vibration and jamming, reducing the wear of the spool valve, greatly extending the service life, and significantly improving the commutation stability, ensuring that the system can operate reliably under various working conditions; In the present invention, the control logic is simplified: The first proportional electromagnet and the second proportional electromagnet independently control the gears, and five stable states can be achieved through different gear combinations, and then the oil circuit connection relationship between the eight ports can be dynamically switched; this innovative design simplifies the control logic, can more conveniently support the parallel operation of multiple actuators, meets the complex requirements of the coordinated operation of multiple actuators such as construction machinery, and improves the control accuracy and flexibility of the system; The present invention has excellent leakage control: the large spool shoulder adopts an asymmetric variable cross-section design, which is precisely matched with the gradient layout of the annular oil groove in the valve body. At a rated pressure of 35 MPa, the internal leakage is ≤ 0.1 L / min, effectively reducing the oil leakage. At the same time, a filled polytetrafluoroethylene sealing ring is added at the sliding key connection, further reducing the internal leakage, improving the sealing performance and reliability of the hydraulic system, and ensuring the efficient and stable operation of the system. The present invention has an accelerated response speed: thanks to the double spool linkage design and the coordinated drive of electromagnetic force and independent return springs, the inertia and frictional resistance of the spool movement are effectively reduced. Compared with traditional electromagnetic directional control valves, the commutation action time is significantly shortened, which is suitable for high-frequency commutation and high-precision control scenarios, can quickly and accurately achieve oil circuit switching, meet the strict requirements of the system for response speed, and improve the overall performance of the system.

[0014] In order to more clearly elaborate on the structural features and functions of the present invention, the present invention will be described in detail below in conjunction with the drawings and specific embodiments. Brief Description of the Drawings

[0015] Figure 1 is a three-dimensional structural schematic diagram of the whole of the present invention; Figure 2 is a sectional structural schematic diagram of the present invention; Figure 3 is a three-dimensional structural schematic diagram of the valve body assembly of the present invention; Figure 4 is a three-dimensional structural schematic diagram of the large spool of the present invention; Figure 5 is the hydraulic symbol schematic diagram of the present invention In the figure: 1. Valve body assembly; 101. Main cavity; 102. Annular oil groove; 103. Radial oil guiding hole; 2. Double spool coordinated structure; 201. Large spool; 202. Small spool; 203. Main oil passage; 204. Shoulder; 205. Sliding key; 206. Radial oil through hole; 3. Electromagnetic drive and return mechanism; 301. First proportional electromagnet; 302. Second proportional electromagnet; 303. Large spool return spring; 304. Small spool return spring; 305. First push rod; 306. Second push rod. Detailed Description of the Embodiments

[0016] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The following describes the specific implementation of the present invention in detail in conjunction with specific embodiments.

[0018] Such as Figures 1-5As shown in the figure, an embodiment of the present invention provides a five-position eight-way electromagnetic reversing valve, which includes a valve body assembly 1, a double spool cooperative structure 2, and an electromagnetic driving and reset mechanism 3. The valve body assembly 1 is cast from high-strength cast iron or aluminum alloy. The base material of the valve body assembly 1 is selected as high-strength ductile iron, and through a specific heat treatment process, the material meets the specified excellent hardness and tensile strength requirements. The internal main cavity 101 is a cylindrical through hole, and the surface roughness Ra of the inner wall surface is ≤0.4 μm, forming a high-precision sliding seal pair with the large spool 201. During the processing of the internal main cavity 101, a special tool is used for deep hole drilling, and it is carried out under preset precise cutting parameters. The inner wall is processed by precision honing technology and surface hardening treatment, strictly meeting the high-precision requirements of hole diameter tolerance, surface roughness, and plating requirements, ensuring the high quality and reliability of the valve body. The axial distance between the first oil inlet P1 and the second oil return port T2 on the upper side of the valve body is L1, and the axial distance between the second oil inlet P2 and the first oil return port T1 on the lower side is L2, and L1 = L2. The connecting lines of the oil inlet and outlet holes on the upper and lower sides are distributed in a parallelogram to ensure uniform oil distribution. The distance between the two pairs of oil outlet ports A1 / B1 and A2 / B2 on the left and right sides is L3, which is used to connect the two-way working chambers of the hydraulic actuator. The annular oil groove 102 on the inner wall of the main cavity 101 is connected to the external oil port through the radial oil guiding hole 103. The inner wall of the radial oil guiding hole 103 is plated with hard chromium to reduce the flow resistance. The oil outlet ports A1 / B1 and A2 / B2 are connected to the main cavity 101 through the annular oil groove 102 to achieve corresponding functions. The cylindricity of the main cavity 101 of the valve body is ≤0.005 mm, and the axial tolerance of the annular oil groove is ±0.02 mm, strictly ensuring the manufacturing accuracy of the valve body. During the processing of the oil port and the flow channel, the high and low pressure oil ports adopt standard thread interfaces, and the flow channel is designed with specific angles and structures to effectively reduce the flow resistance. The flow channel of the working oil port adopts an optimized fluid structure and the inner wall is polished. The annular oil groove system forms multiple groups of gradient oil grooves with different widths on the inner wall of the main cavity through numerical control machining. Each group of oil grooves is connected to the external oil port through evenly distributed oil guiding holes to achieve precise oil distribution and efficient oil flow. The double spool cooperative structure 2 is composed of a large spool 201 and a small spool 202 nested coaxially. The large spool 201 is a stepped shaft structure, and there are three shoulders 204 on the outer surface, which cooperate with the annular oil groove of the valve body to realize the oil circuit switching. It is driven by the first proportional electro-magnet 301 with a stroke of 5 ± 0.1 mm. The small spool 202 is connected to the large spool 201 through an axial sliding key 205. The sliding key 205 limits its displacement range relative to the large spool 201. There is a radial oil through hole 206 at the front end, which is connected to the main oil passage 203. It is driven by the second proportional electro-magnet 302 with a stroke of 1.2 ± 0.05 mm and a repeat positioning accuracy of ±0.01 mm. Reset springs are installed at the ends of the two spools respectively. The stiffness of the reset spring of the large spool is k1 = 80 - 90 N / mm, and the pre-tightening force F1 = 100 - 130 N. The stiffness of the reset spring of the small spool is k2 = 50 - 60 N / mm, and the pre-tightening force F2 = 70 - 90 N. The processing materials of the large spool valve 201 and the small spool valve 202 are selected as specific alloy steels, and the surface hardness and wear resistance are significantly improved after nitriding treatment; during machining, key parts such as the outer diameter, total length, oil passage and shoulder are precisely machined and surface strengthening treatment is implemented. The machining of the sliding key groove meets the high-precision geometric tolerance requirements to ensure the high-precision manufacturing of the spool valve; the nested structure of the small spool valve 202 and the large spool valve 201 forms a precise clearance fit with the main oil passage, and the oil passage interconnection design is realized through radially distributed through holes. The sliding key is assembled with high-strength materials and surface coating treatment is carried out to effectively reduce friction; a sealing ring made of special materials is used and micro-textures are machined on the surface to form a hydrodynamic lubricating film, strengthening the dynamic sealing performance and ensuring the sealing and stability of the spool valve during movement.

[0019] The electromagnetic drive and reset mechanism 3 includes two sets of first proportional electromagnets 301 and second proportional electromagnets 302 with excellent performance, and the adapted large spool valve reset spring 303 and small spool valve reset spring 304. The first proportional electromagnet 301 and the second proportional electromagnet 302 drive the large spool valve 201 and the small spool valve 202 respectively through the first push rod 305 and the second push rod 306; the driving force range of the first proportional electromagnet 301 and the second proportional electromagnet 302 is 0 - 220N, and the response time ≤ 5ms; the contact surface between the first push rod 305 and the spool valve end face has an anti-friction coating 306, and the material is molybdenum disulfide MoS2 or polytetrafluoroethylene PTFE; the large spool valve reset spring 303 and the small spool valve reset spring 304 are respectively installed at the ends of the large spool valve 201 and the small spool valve 202 for the reset of the large spool valve 201 and the small spool valve 202 after power-off; the first proportional electromagnets 301 and the second proportional electromagnets 302 at both left and right ends each have four gears, and diverse oil passage control logics are realized through different gear combinations.

[0020] The working principle and usage process of the present invention: The five-position eight-way electromagnetic reversing valve realizes the oil passage switching in five positions through the coordinated movement of the large spool valve 201 and the small spool valve 202, in cooperation with the electromagnetic drive and reset mechanism 3; There are 5 radial through holes at the front end of the small spool valve 202, which are connected to the main oil passage of the large spool valve 201 and the oil outlet holes of the valve body assembly 1, ensuring that when the large spool valve 201 and the small spool valve 202 work simultaneously, high-pressure oil can be supplied to both spool valves at the same time, enabling the oil to flow out smoothly from the left and right side outlet ports; Position state Ⅰ: In the initial state, the first proportional electromagnets 301 and the second proportional electromagnets 302 on both left and right sides are not energized. At this time, the large spool valve 201 and the small spool valve 202 are in the initial position under the action of the large spool valve reset spring 303 and the small spool valve reset spring 304; the shoulder 204 of the large spool valve 201 completely closes all oil ports, preventing the system pressure oil from entering the actuator oil passage, and isolating the return oil passage from the pressure oil passage, thus realizing the equipment shutdown protection or emergency braking function; Position II: When the first proportional electromagnet 301 and the second proportional electromagnet 302 are in the first gear position, the electromagnetic force generated by the first proportional electromagnet 301 pushes the large valve core 201 to move to the right through the first push rod 305. As the large valve core 201 moves to the right, its shoulder 204 changes the connection state of the oil port, so that the first oil inlet P1 is directly connected to the first oil return port T1, and the second oil inlet P2 is directly connected to the second oil return port T2, realizing a dual-path unloading function; in this state, the pressure oil in the system can smoothly return to the oil tank through these two paths, which is suitable for no-load operation of the hydraulic pump or standby state of the equipment, and can reduce system energy consumption and reduce the heat generated by oil circulation friction; Position III: When the first proportional solenoid 301 and the second proportional solenoid 302 are switched to the second gear, the first proportional solenoid 301 further pushes the large valve core 201 to move rightward, and at the same time, the second proportional solenoid 302 pushes the small valve core 202 to move relative to the large valve core 201 through the second push rod 306. At this time, the main oil passage 203 inside the large valve core 201 and the four groups of oil outlets A1, B1, A2, and B2 are connected through the radial oil hole 206 at the front end of the small valve core 202, that is, the first oil inlet P1 is connected to the four groups of oil outlets A1, B1, A2, and B2 through the parallel oil passage inside the valve core, so as to realize synchronous oil supply to multiple actuators. Since different actuators may have different loads, a diverter valve or a balancing valve is required to ensure uniform distribution of oil flow. This position is typically used in multi-cylinder synchronous lifting systems and engineering machinery requiring compound actions. Position IV: In this position, the first proportional solenoid 301 and the second proportional solenoid 302 are in a specific state, and the large valve core 201 and the small valve core 202 move to the corresponding position. At this time, the shoulder 204 of the large valve core 201 closes the P1 oil port, and only the second oil inlet P2 is connected to the second oil return port T2. It is suitable for unloading the second hydraulic pump separately in the dual-pump hydraulic system, while the main pump can continue to supply oil to realize partial function operation, so as to achieve the purpose of energy-saving control; Position V: In this position, the first proportional solenoid 301 and the second proportional solenoid 302 adjust the large valve core 201 and the small valve core 202 into place, and the shoulder 204 of the large valve core 201 realizes the connection from P1 to T1, while closing the P2 oil port. This state is used for unloading the main oil circuit of a single-pump system, or for a dual-pump system to release the main pump pressure first and retain the standby pressure reserve of the backup pump, which is common in intermittent working equipment that requires rapid load switching.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A five-position eight-way electromagnetic directional valve, comprising a valve body assembly (1), a double spool cooperative structure (2), and an electromagnetic drive and reset mechanism (3), characterized in that: The valve body assembly (1) is cast with high-strength materials. A first oil inlet P1 and a second oil return port T2 are provided above the valve body assembly (1), and a second oil inlet P2 and a first oil return port T1 are provided below the valve body assembly (1). Two pairs of oil outlets (A1 / B1, A2 / B2) are symmetrically distributed on the left and right sides of the valve body assembly (1); an axially penetrating main cavity (101) and several radial oil guide holes (103) are provided inside the valve body assembly (1). An annular oil groove (102) is precision machined on the inner wall of the main cavity (101), and the radial oil guide holes (103) are ingeniously connected to the external oil ports. The double spool cooperative structure (2) is composed of a large spool (201) and a small spool (202) nested coaxially; the large spool (201) is a carefully designed stepped shaft structure. An axially penetrating main oil passage (203) is provided inside the large spool (201), and three shoulders (204) are precisely machined on the outer surface of the large spool (201); the small spool (202) is connected to the large spool (201) through an axial sliding key (205). The sliding key (205) precisely limits the displacement range of the small spool (202) relative to the large spool (201), and a radial oil passage hole (206) is provided at the front end of the small spool (202) and is connected to the main oil passage (203). The electromagnetic drive and reset mechanism (3) includes two sets of first proportional electromagnets (301) and second proportional electromagnets (302) with excellent performance, and a large spool return spring (303) and a small spool return spring (304) that match. The first proportional electromagnet (301) and the second proportional electromagnet (302) drive the large spool (201) and the small spool (202) to be connected through a first push rod (305) and a second push rod (306) respectively. The large spool return spring (303) and the small spool return spring (304) are respectively installed at the ends of the large spool (201) and the small spool (202).

2. The five-position eight-way electromagnetic directional control valve according to claim 1, wherein: The axial strokes of the large spool (201) and the small spool (202) are precisely designed to satisfy the following relationship: the maximum displacement stroke L1 of the large spool (201) = 5 ± 0.1 mm, and the maximum relative displacement stroke L2 of the small spool (202) = 1.2 ± 0.05 mm; the keyway length of the sliding key (205) is precisely designed to be L2, which precisely limits the displacement range of the small spool (202) and ensures the accuracy of the spool movement.

3. The five-position eight-way electromagnetic directional control valve according to claim 1, characterized in that: The widths of the variable cross-section shoulders (204) of the large spool (201) are optimized and designed to be 2.4 mm, 1.6 mm, and 2.4 mm respectively, which are perfectly adapted to the oil passages of the valve body, realizing the high efficiency of oil circuit switching.

4. The five-position eight-way electromagnetic directional valve according to claim 1, characterized in that: The stiffness k1 of the large spool return spring (303) = 80 - 90 N / mm, and the pre-tightening force F1 = 100 - 130 N; the stiffness k2 of the small spool return spring (304) = 50 - 60 N / mm, and the pre-tightening force F2 = 70 - 90 N, ensuring the stability and reliability of the spool reset.

5. The five-position eight-way electromagnetic directional control valve according to claim 1, characterized in that: The driving force range of the first proportional electromagnet (301) and the second proportional electromagnet (302) is 0 - 220 N, and the response time is extremely short, ≤5 ms. High-performance anti-friction coatings are provided on the contact surfaces between the first push rod (305) and the end face of the large spool valve (201) and between the second push rod (306) and the end face of the small spool valve (202). The coating material is molybdenum disulfide (MoS2) or polytetrafluoroethylene (PTFE), which reduces friction and improves the driving efficiency.

6. The five-position eight-way electromagnetic directional control valve according to claim 1, characterized in that: The first proportional electromagnet (301) and the second proportional electromagnet (302) at both the left and right ends each have four gears. Through different gear combinations, diverse oil circuit control logics are achieved.

7. The five-position eight-way electromagnetic directional control valve according to claim 1, wherein: A high-quality sealing ring (208) is provided at the connection of the sliding key (205). The material of the sealing ring is filled polytetrafluoroethylene, which has a wide working temperature range of -40°C to +150°C and can withstand a pressure ≥35 MPa, effectively preventing oil leakage and improving the sealing performance.

8. The five-position eight-way electromagnetic directional control valve according to claim 1, characterized in that: The inner wall of the main cavity (101) is specially treated with a uniform hard chromium layer (104) with a thickness of 15 - 25 μm and a surface roughness Ra ≤0.2 μm. The surfaces of the large spool valve (201) and the small spool valve (202) are nitrided with a nitrided layer depth ≥0.25 mm and a hardness ≥HRC58, enhancing the wear resistance and corrosion resistance of the valve body and the spool valve.

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