Source analysis and solution of hydraulic system noise

The working principle of the hydraulic system: After the pressure oil output by the hydraulic pump 4 passes through the oil filter 5, part of it enters the A tube (disc brake), and part of it enters the pressure regulating circuit composed of the relief valve 8 and the electro-hydraulic proportional pressure valve 14. The function of the electro-hydraulic proportional pressure valve 14 is equivalent to the pilot valve of the relief valve 8. By continuously adjusting the control current input of the electro-hydraulic proportional pressure valve 14, the continuous adjustment of the oil pressure of the main oil circuit can be realized, and then the continuous adjustment of the braking force can be realized, and the continuous control of the braking process can be realized. The main control element of the hydraulic brake system of this structure is the electro-hydraulic proportional pressure valve, which is easy to realize pressure control and strong anti-pollution ability. The dynamic response of the system is fast, and the safety and reliability are high.

1, hydraulic station noise causes and noise reduction processing

The hydraulic station is the heart of the lifting mechanism, which reliably ensures the safe operation of the lifting system. But the noise produced by its hydraulic system also increases. Noise is very harmful to people's health and seriously affects the physical and mental health of the elevator driver. How to eliminate noise and reduce the harm of noise is an urgent problem to be solved. Based on years of work experience, the author has conducted a preliminary discussion on the causes of noise and how to reduce noise, and summarized that the main reasons for noise are as follows:

2, air into the hydraulic system

When the hydraulic system invades the air, the gas is mixed in the hydraulic oil, and the volume changes with the change in the pressure of the hydraulic oil, when the flow to the high pressure area is compressed, the volume suddenly decreases, and when it flows into the low pressure area, the volume suddenly increases, the sudden change in the volume of the bubble, resulting in an "explosion" phenomenon, thus producing noise, this phenomenon is usually called "hole". "Hole" not only causes vibration and noise, but also destroys the continuity of the fluid, reduces the physical characteristics of the medium, while reducing the efficiency of the system, the deterioration of dynamic characteristics, seriously affecting the transmission of liquid pressure, brake performance is not good, brake lag, but also easy to cause the elevator speeding, over-winding or braking and other accidents, should be paid enough attention to.

For this reason, the commonly used method to reduce noise is: set an exhaust device on the connection pipeline or the actuator, often check the residual gas in the system and clean the system, when the noise occurs, open the exhaust hole in time to discharge the air in the system, which can effectively eliminate noise.

3, hydraulic pump or hydraulic motor own characteristics or quality defects

Hydraulic pump and hydraulic motor are the main parts that produce noise in hydraulic transmission. The main causes of noise are: (1) the flow pulsation and pressure pulsation of the pump or motor, resulting in vibration of the pump components. This vibration (the future development of the vibrating screening machinery industry) can sometimes produce resonance. The resonant frequency can be 2 to 3 times the flow pulsation frequency or greater, and the basic frequency of the pump or motor and its resonant frequency are consistent with the natural frequency of the mechanical or hydraulic, then the noise will be greatly increased. The results show that the effect of increasing speed on noise is generally greater than that of increasing pressure.

(2) When the working chamber of the pump or motor is suddenly connected with the oil pressure chamber from the oil suction chamber, or the oil pressure chamber is suddenly connected with the oil suction chamber, the oil flow and pressure are sudden changes, which has a great impact on the noise.

(3) Hole phenomenon. When the pressure in the oil suction chamber of the pump or motor is less than the air separation pressure at the temperature of the oil, the air dissolved in the oil will precipitate into bubbles. When the oil with bubbles enters the high pressure chamber, the bubbles will be broken, forming a local high frequency pressure impact, resulting in noise.

(4) The flow channel in the pump or motor has a sudden expansion and contraction of the cross section, sharp bends, and the cross section of the channel is too small, resulting in liquid turbulence, vortices and jets, which increases the noise.

(5) In the use of the pump or motor, due to the wear of the hydraulic pump parts, the gap is too large, the flow is insufficient, and the pressure is easy to fluctuate, which will also cause noise. For this reason, common noise reduction measures are:

(5-1) Eliminate sharp changes in oil pressure inside the hydraulic pump.

(5-2) In order to absorb the hydraulic pump flow and pressure pulsation, a silencer can be installed at the outlet of the hydraulic pump.

(5-3) To prevent the cavitation of the pump, a large diameter suction pipe can be used to reduce the local resistance of the pipeline; A large capacity oil suction filter is used to prevent the oil from mixing air.

(5-4) Reasonable design of hydraulic pump, improve the stiffness of parts.

4. Improper adjustment of the reversing valve

The flow regulation of the reversing valve is not appropriate, or the voltage of the solenoid reversing valve coil does not match, so that the reversing valve spool moves too fast, or the valve spool is blocked, causing the reversing impact and causing noise.

If there is noise caused by this situation, when the reversing valve is a hydraulic reversing valve, the throttling element in the control oil circuit should be adjusted to make the reversing smooth without impact. In addition, because the reversing valve is working, the spool is supported on the spring, when its frequency is similar to the hydraulic pump oil pulsation frequency or other vibration source frequency, it will cause vibration and noise. At this time, by changing the natural frequency of the pipeline system, changing the position of the control valve or adding the accumulator appropriately, the effect of vibration and noise reduction can also be produced.

The relief valve is faulty

The failure of the relief valve can also make the system produce noise, such as the spool and the valve hole are not properly matched, the contact between the cone valve and the seat is stuck by dirt, the damping hole is blocked, the spring is crooked or fails, so that the spool is stuck or the movement in the valve hole is not flexible, causing system pressure fluctuations and noise.

If this happens, the relief valve should be repaired in time. Pay attention to cleaning and dredging Yin hole. Check the relief valve, if found to be damaged, or due to wear exceeds the provisions, it should be repaired or replaced in time; 2.5 Mechanical reasons Mechanical reasons are also the main part of the noise generated by the system:

Mechanical noise caused by mechanical vibration such as unbalance of rotating part, bad bearing and bending of pump shaft.

The pipe is long and the elbow is not fixed, which is easy to cause the pipe to shake when the oil flow passes through, especially when the flow rate is high.

The pipe and hydraulic station are rigidly connected to transmit the mechanical vibration of the motor and hydraulic pump. For this reason, the following methods should be adopted to reduce noise

Adjust the installation accuracy of motor and hydraulic pump; Reinstall the coupling to ensure that the coaxiality meets the requirements.

Longer tubing should be separated from each other, and a supporting pipe frame should be added in the middle.

The pump mounted on the fuel tank should be cushioned by rubber pads.

A section of the outlet pipe of the hydraulic station uses a rubber hose to isolate the connection between the hydraulic station and the pipeline.

5. The noise generated by the hydraulic system of the hoist not only affects the physical and mental health of the operating driver, but also seriously affects the safe operation of the hoist. In the coal mine use site, the training of maintenance personnel should be strengthened, the maintenance level should be improved, the normal operation of equipment should be ensured, the adverse factors caused by noise should be eliminated in time, and the noise should be reduced. Ensure the safe operation of the hoist and create a pleasant working environment.

Four column hydraulic press