The hottest VDL thread cartridge safety valve

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VDL type thread cartridge safety valve (hereinafter referred to as VDL type safety valve) is a newly developed pilot relief valve developed by Qingzhou Hydraulic Parts Factory Co., Ltd. on the basis of digesting and absorbing foreign advanced hydraulic valve technology. The structure is obviously different. The main structural features are as follows: (1) the main valve core inner hole guide combined sealing structure is adopted; (2) The inner hole of the main valve core and the conical surface are two-stage concentric seals; (3) Secondary damping of damping hole and annular damping slot. VDL type safety valve has the functions of overload protection and oil replenishment. It has been used in batch on the multi-channel directional valve of the hydraulic system of loaders, combine harvesters and other working devices. It has excellent performance and reliable operation, and can well meet the performance requirements of the whole machine. 1. Main performance parameters: pressure regulation range (MPA) 8--25 nominal flow (l/min) 100 opening ratio =94% closing ratio =90% pressure swing (MPA) =0.5 overflow flow (l/min) =1 transient recovery time (s) =0.12 structure composition the structure composition of VDL safety valve is shown in Figure 1. 1. pilot valve seat

2 Pressure regulating spring

3 Pilot valve element

4 Combined seal

5 Return spring

6 Main valve element

7 Slide valve

8 Working principle of the connecting sleeve 3 when the inlet pressure P of the safety valve exceeds its set pressure value, the pilot valve element 3 is opened, and the oil passes through the small damping effect of the hole in the center of the slide valve 7, so that the pressure P1 in the rear chamber of the slide valve 7 is slightly lower than the oil inlet pressure P. the slide valve 7 moves left without the weak force of the return spring 5 under the p--p1 pressure difference until the pilot valve element 3 is close. At this time, The force of oil inlet pressure P on slide valve 7 is directly transmitted to pilot valve element 3, which further increases the pilot valve element 3. At the same time, since pilot valve element 3 blocks the central hole of slide valve 7, oil can only flow through the annular gap between slide valve 7 and main valve element 6. The damping effect of this ring gap is far greater than that of the central hole of the slide valve 7, which rapidly reduces the P1 pressure. Mainly affected by the raw ore export restriction policies of Indonesia and other countries, the valve element 6 quickly moves to the left along the pilot valve seat 1 with its inner hole guide under the p--p1 pressure difference, playing the role of safety overload protection. During the above process, the return oil after pilot valve element 3 is opened passes through α Through the gap between the main valve core 6 and the connecting sleeve 8, it flows to the oil return port for oil return. When the inlet pressure P is lower than the return oil pressure pt--p, the main valve element 6 is opened to reverse the flow of the return oil port and realize the oil replenishment function. If the influence of the self weight and friction force of the main valve core is ignored, The force balance equations under each limit state in the above working process are as follows: force balance equation when the slide valve is about to move but not to move π/4 · D22 (p-p1) =ky0 force balance equation when the slide valve is about to move but not to move up the pilot valve: force balance equation when π/4 · D22 (p-p1) =ky0 (y0-l0) force balance equation when the main valve core is about to move but not to move π/4 · D22 (p-p1) p= π/4 (d2-d22) p1+f0 force balance equation when the main valve core is about to move but not to move at the beginning of oil makeup π/4 (d02-d2) (P0 T-P) =In ky0 formula, p--- inlet pressure of safety valve, MPa, p1--- back cavity pressure of slide valve, MPa, pt--- return port pressure, MPa, d2--- slide valve diameter, mm, d--- seat hole diameter of main valve core, mm, d--- inner diameter of main valve core, mm, d0--- outer diameter of main valve core, mm, k--- return spring stiffness, n/mm, y0--- pre compression shrinkage of return spring, mm, l0--- slide valve stroke, mm, f0--- friction force of combined seal, n. The calculation formula of oil inlet and return flow rate after the main valve core is opened is as follows: oil inlet flow rate v1=66.667 · q/π · D2 (m/s) oil return flow rate v2=66.667 · q/n · π · D32 (m/s), where Q - flow through the valve, l/min, D3 - diameter of all human organs, mm, N - diameter and quantity of oil return holes 4. The opening and closing characteristics are adjusted at constant pressure p=16mpa Nominal flow q=100l/min2) the longitudinal stress of the section near the center line of the box girder at the supporting position is greater than that at the web. When the load can no longer rise, according to the measured p--q corresponding value during the opening and closing process, the starting characteristic curve of the safety valve can be drawn as shown in Figure 2. Curve 1 in the figure is the opening process and curve 2 is the closing process. Conclusion (1) the VDL safety valve is designed with compact and reasonable structure, small volume and convenient disassembly and assembly. From the analysis of test use, the safety valve has good opening and closing characteristics, small pressure swing and no noise. It can be widely used as safety valve, overload valve and oil makeup valve in hydraulic systems such as engineering machinery, agricultural machinery and mining machinery. (2) Since the VDL safety valve adopts the two-stage concentric sealing structure of inner hole and conical surface, the sealing directly affects the static and dynamic characteristics of the safety valve. The coaxiality of inner hole and conical surface is required to be small, while the inner hole is a blind hole with small aperture, so it is difficult to ensure the coaxiality of the two and difficult to process

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