예상 읽기 시간: 8 분

Hydraulic Circuit using a pressure-reducing valve Figure 15 allows a cylinder or stroke in the circuit to operate at a low relief valve set pressure. A pressure-reducing valve with a check valve is designed so that when the piston returns, the oil flow passes through the check valve without passing through the pressure-reducing element. Hydraulic Circuit

1. 문제에 주의를 기울이는 감압 회로의 설계

• Leakage problem of pilot operated pressure reducing Hydraulic Circuit

Be aware of the pilot-operated pressure reducing valve leakage than other control valves. The leakage of this valve can be as much as 1L / min or more. As long as the valve is in working condition, the leakage is always present. In the choice of hydraulic pump capacity, take this into full consideration. It should note that the minimum adjustment pressure of the pressure-reducing valve should ensure that the difference between the primary and the secondary is 0.31MPa. Hydraulic Circuit

• 2차 압력 불안정 문제

The damping hole of the main spool of the pressure reducing valve is blocked so that the oil exported from the pressure reducing valve cannot flow smoothly into the capacitive cavity between the main valve and the pilot valve. And the pilot valve also reduces the control role of the secondary pressure exported from the pressure reducing valve, resulting in unstable secondary pressure. Hydraulic Circuit

2. Decompression Hydraulic Circuit component setting problem

As shown in Figure 16, the pressure in the branch circuit cylinder 2 after the pressure-reducing valve 3 is lower than the fluid pressure in the master cylinder 1 branch circuit, which is called a pressure reducing circuit. The problems of this circuit are as follows. Hydraulic Circuit

• When cylinder 2 is stopped for a long time, the secondary pressure after pressure reducing valve 3 gradually increases. This is because when cylinder 2 is stopped for a long time, a small amount of oil is discharged through the pilot valve through the spool gap to keep the valve in working condition. Due to the leakage in the valve, the flow through the pilot valve increases, and the secondary pressure (outlet pressure) of the pressure-reducing valve increases. To prevent this failure, you can add the oil circuit shown in the dashed line in the pressure reducing circuit, and install a safety valve at b to ensure that the pressure reducing valve outlet pressure does not exceed its adjustment Hydraulic Circuit.

• The speed adjustment of the hydraulic cylinder in the pressure reducing circuit is not working or the speed is not stable. As shown in Figure 16, this problem occurs when the leakage of pressure-reducing valve 3 (the fluid flowing back to the tank from the pressure-reducing valve drain port) is large. The solution is to change the throttle valve from the position in the figure to connected in series at an after the pressure reducing valve, to avoid the effect of pressure reducing valve leakage on the speed of cylinder 2. Hydraulic Circuit

3. 감압 회로의 불안정한 작동 압력

In the system shown in Figure 17, the hydraulic pump is quantitative, and the hydraulic cylinders 7 and 8 in the main oil circuit are controlled by two-position four-way electro-hydraulic reversing valves 5 and 6 respectively to control the direction of motion, and the control fluid of the electro-hydraulic reversing valves comes from main oil Hydraulic Circuit.

감압 회로는 메인 오일 회로와 병렬로 연결되며 감압 밸브 3에 의해 감압됩니다. 2 위치 4 방향 솔레노이드 밸브는 유압 실린더 9의 이동 방향을 제어합니다.

The electro-hydraulic reversing valve controls the return line of the oil circuit and the external drain of the pressure reducing valve. The oil circuit merges and return to the tank, and the operating pressure of the system is regulated by the relief valve2. Hydraulic Circuit

The main oil circuit in the system works normally, but in the pressure reducing circuit, the pressure downstream of the pressure reducing valve fluctuates greatly, so that the working pressure of hydraulic cylinder 9 cannot be stabilized at the regulated pressure value of 1MPa. Hydraulic Circuit

In the pressure reducing circuit, the downstream pressure of the pressure reducing valve, the working pressure of the pressure reducing circuit, occurs in large fluctuations is a frequent failure phenomenon, the main reasons for which are the following. Hydraulic Circuit

• The prerequisite for a pressure reducing valve to be able to stabilise the pressure downstream of the valve at the regulated value is that the upstream pressure of the pressure reducing valve should be higher than the downstream pressure, otherwise the pressure downstream of the pressure reducing valve cannot be stabilised. Main hydraulic circuit working pressure change significantly. Hydraulic Circuit

It will have a larger impact if the minimum pressure value changes lower than the downstream pressure of the pressure-reducing valve, this is because when the upstream pressure of the pressure reducing valve is increase, the downstream pressure may have to be increase instantaneously, but through the regulating action of the pressure reducing valve it will quickly return to the regulating valve. Conversely, when the upstream pressure of the pressure-reducing valve reduces, the downstream pressure of the pressure-reducing valve should reduce instantaneously, and the pressure-reducing valve will quickly adjust so that the downstream pressure rises to the regulated value. Hydraulic Circuit

상류 압력이 변동하고 최소 압력이 하류 압력의 고정 값보다 낮으면 그에 따라 하류 압력을 감소시켜야 하며 규정된 압력 값으로 안정화될 수 없습니다.

따라서 작동 조건의 주유 회로 액츄에이터 부하 변화에서 최소 작동 압력이 압력 하류 압력보다 낮을 때 회로 설계는 체크 밸브를 추가하고 상류측 압력이 하류측 압력 이하로 변화하는 것을 방지하기 위해 체크 밸브 및 감압 밸브 등.

• 액추에이터의 부하가 불안정합니다. 감압 회로에서 하류 압력은 감압 밸브의 조절 효과로 인해 안정적입니다. 액츄에이터에 충분한 부하가 있으면 하류 압력은 여전히 객관적인 법칙을 따라야 합니다. 즉, 압력은 부하에 의해 결정되어야 합니다. 부하가 없으면 압력이 형성되지 않으며 부하가 낮으면 압력이 낮아집니다. 감압 회로의 경우 감압 밸브 후의 압력은 특정 순간에 부하 조건 하에서 설정되지만 감압 회로의 작동 과정에서 부하가 감소되면 감압 밸브의 하류 압력은 0까지 줄입니다. 부하가 다시 증가하면 감압밸브의 하류측 압력이 증가하고, 부하에 따라 감압밸브의 조절압력까지 압력이 증가하면 압력은 부하와 함께 증가하지 않고 조절압력으로 유지된다. 감압 밸브의 값.

따라서 가변 부하 조건에서 감압 밸브의 하류 압력 값은 변하며 이 변동은 감압 밸브의 조절 값보다 낮을 수 있지만 조절 값보다 높을 수는 없습니다.

• 외부 드레인 라인에 배압이 있습니다. 감압 밸브의 제어 라인은 외부 배수 라인입니다. 제어 유체는 콘 밸브를 밀어 열고 별도로 탱크로 돌아갑니다. 외부 드레인 라인에 배압이 변화하면 콘 밸브를 누르는 압력유의 압력에 직접적인 영향을 주어 압력 변화를 일으켜 감압 밸브의 하류 작동 압력을 변화시킵니다.

그림 17과 같은 시스템의 고장 현상은 점검을 통해 분석한 것으로, 감압밸브 외부 배수유 회로의 배압 변화로 인한 것이다.

It is easy to see that the electro-hydraulic reversing valves 5 and 6 in the system is changing in the process of reversing the flow and pressure of the return oil in the control oil circuit. The oil in the external drainage circuit of the pressure-reducing valve is also fluctuating, and the two streams of oil merge to produce unstable backpressure.

After debugging, when the electro-hydraulic reversing valves 5 and 6 act at the same time, the pressure gauge 10 reads 1.5 MPa. This is because the electro-hydraulic reversing valve is under the action of a high-pressure control fluid, the instantaneous flow is larger, and in the case of a longer drain pipe, higher backpressure is generated, the backpressure increases. So that the main valve opening of the pressure reducing valve increases, and the local pressure at the valve opening decreases, so the working pressure of the pressure reducing valve increases.

이 결함을 제거하려면 감압 밸브의 드레인 라인과 전자 유압식 반전 밸브 5 및 6을 별도로 오일 탱크에 다시 연결해야 감압 밸브의 드레인 라인이 간섭없이 오일 탱크로 안정적으로 다시 흐를 수 있고 변동하고 하류 압력은 규정된 압력 값에서 안정될 것입니다.

위의 분석은 시스템을 설계하고 설치하는 동안 구성 요소의 작동 성능을 이해하면서 구성 요소가 서로 간섭하는지 여부를 신중하게 고려해야 함을 보여줍니다.

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