**Abstract:**
This paper presents an optimal structural model for a pilot pressure valve, which offers high precision and stability. This design can be applied to conventional pilot-operated relief valves, sequence valves, and pressure-reducing valves, integrating them into a single, universal pilot pressure valve system. The proposed model simplifies the overall structure while enhancing performance. Key words: Pilot pressure valve; Optimal structural model; Precise zero-difference control; Universal pilot valve; Stability margin.
**Introduction:**
Most existing pilot-operated pressure valves follow traditional design principles. However, this paper introduces a patented best structural model that significantly improves accuracy and stability. By modifying conventional pilot-operated relief valves, sequence valves, and pressure-reducing valves, they can all be transformed into a unified pilot pressure valve with a common pilot valve. This approach not only reduces complexity but also enhances efficiency and reliability in various hydraulic applications.
**Pilot Pressure Valve Structure and Function:**
Figure 1 illustrates the structure of a pilot relief valve. The relationships between key parameters are defined as follows:
Kt2(Y20 + Y2) = p1A2 - Ky2Y2p2 - Fr2Q = KQY1p1
Kt1(Y10 + Y1) = (p1 - p2)A1 - p2(A3 - A1) - Ky1Y1p1 - Ff1q = KqY2p1 / 2 - qj
q = Kd(p1 - p2)^{1/2}d^2e
Where:
- Kt2, Kt1: spring stiffness of main valve
- Y20, Y10: pre-compression of pilot and main valve springs
- Y2, Y1: displacement of pilot and main valve spools
- p1, p2: pressure at main and pilot valve ports
- Ky2Y2p2, Ky1Y1p1: steady-state hydraulic forces
- Ff2, Ff1: friction forces of pilot and main spool
- Q, q: flow through main and pilot valves
- KQ, Kq, Kd: structural constants
- qj: leakage from pilot valve guide piston
- A1, A2, A3: cross-sectional areas of main and pilot valve ports
- de: differential orifice size of main valve
The pilot flow is regulated through a separate orifice E, which does not affect the speed of pressure wave transmission. The pilot valve core and main spool each have their own damping orifices D and F, ensuring smooth operation. The size of these orifices influences the movement speed but not the pressure regulation accuracy. The pilot valve is directly driven by the control pressure, eliminating partial pressure loss. Its opening pressure is much lower than conventional designs, and the pressure difference required to open it is minimal—only a few atmospheres. This leads to reduced pressure drop at the pilot valve port and improved overall efficiency.
The main valve is fully actuated by the pressure difference created by the control flow, with no pressure loss. The control flow mainly causes a pressure drop between the front and back chambers of the main spool and at the pilot valve port. The former has a large pressure drop, allowing the damping orifice E to be minimized for better static characteristics. The size of the differential orifice determines the amount of control flow needed. Since the pilot pressure directly controls the valve opening, and the three damping orifices operate independently, the structure achieves maximum performance.
The pilot pressure valve opens as follows: when the control pressure increases, the pilot valve opens, allowing the control flow to pass. This flow creates a pressure drop across the main valve’s differential orifice. As the control pressure continues to rise, the pilot valve opens further, increasing the control flow and the pressure drop. When the pressure reaches the main valve’s full-opening threshold, the main spool lifts, allowing the rated flow to pass.
**Performance Characteristics:**
1. **High Precision Control:** Based on the imported structural model, the valve maintains consistent installation dimensions, pressure levels, and orifice sizes. The regulated pressure difference is only 0.1–0.2 bar, and with a smaller orifice, it can be as low as 0.05–0.1 bar. In high-cleanliness systems, the pilot valve can open slightly, achieving near-zero pressure difference for precise control.
2. **Universal Design:** With a uniform design featuring low stiffness and high-strength compression springs, the need for multiple pressure level series is eliminated. This allows the conventional pilot valve to be unified under the best mode, creating a versatile universal pilot valve.
3. **Excellent Stability and Noise Reduction:** By incorporating a spring-oriented sleeve to prevent radial vibration, the pilot valve achieves superior anti-vibration and noise reduction. The special damping holes D and F enhance stability, and by minimizing their aperture, the system ensures rapid response without compromising stability. The presence of the guide sleeve makes the steady-state hydraulic power negligible, enabling precise control over the pilot valve opening based on known technical requirements.
4. **Further Structural Optimization:** To facilitate inspection and ensure interchangeability of main valve components, the main spool and valve sleeve can be designed with low-friction seals, improving long-term performance and maintenance ease.
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