Analysis and modification of the hydraulic circuit

2022-10-15
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Analysis and improvement of hydraulic circuit of normally closed disc brake hydraulic station

Abstract: the hydraulic solution pressure circuit of closed disc brake is analyzed, and a new hydraulic circuit is developed

key words: normally closed; Brake; Hydraulic station; Hydraulic circuit

1 preface

disc brakes have the advantages of compact structure, good adjustability, sensitive action, light weight, small inertia, high safety, good versatility and so on. Moreover, disc brakes are used in pairs, and their error is generally manifested as that the spindle does not bear axial additional force during negative differential braking. During normal braking, the brakes can be divided into two groups, one group can be put into operation first, and the second group can be put into operation after a certain interval, that is, the secondary braking is realized, and the secondary braking makes the braking deceleration generated during braking not too large. Only in the case of safe braking can the two groups be put into braking at the same time to produce the maximum braking torque. If one group fails, there is still another group of brakes working, which will not cause the brake to fail completely

due to the above advantages of disc brake, it is widely used in the braking system of mine hoisting equipment. For example, both multi rope friction hoists and single rope winding hoists use this normally closed disc brake

2 analysis of hydraulic circuit of normally closed disc brake hydraulic station

Figure 1 shows the hydraulic circuit of disc brake hydraulic station for 2JK hoist. The pressure oil discharged from the pump 5 enters the brake cylinder 15 through the oil filter 8, the manual reversing valve 9 and the secondary safety brake valve 11 (charged during normal operation) through the A and B pipes to release the disc brake 16. During the operation of the hoist, in order to keep the disc brake in the released state, the hydraulic system is in the pump on pressure maintaining state. At this time, all the hydraulic oil discharged by the pump flows back to the oil tank through overflow valve 7. During working braking, the pressure of the system is reduced by adjusting the current of the electro-hydraulic pressure regulating device 6, so that the disc brake generates braking torque and participates in the speed control of the hoist. In case of an emergency, the secondary brake safety valve is powered off and the brake cylinder returns oil to realize secondary safety braking

Figure 1 hydraulic system diagram of JK hoist hydraulic station

1 Oil tank 2 Electric contact pressure thermometer (WY) 3 Type oil filter 4 Motor (jdn=2.2kw) 5 Vane pump (yb-asb-fl) 6 Electrohydraulic pressure regulating device 7 Overflow valve (yf-820b) 8 Paper oil filter (zl-25 × 202)9. Manual directional valve 10 Pressure gauge 11 Secondary brake safety valve 12 Pressure relay 13 Five way valve 14 Four way valve 15 Brake cylinder 16 Disc brake

the hydraulic system has the following problems:

(1) when the elevator operates and the building materials industry completes the fixed asset investment of 1.46 trillion yuan, the system needs to start the pump to maintain the pressure. At this time, the motor power turns into the overflow loss of the pump, causing a waste of energy

(2) the overflow loss turns into heat, causing the rise of system temperature, accelerating the oxidation and deterioration of hydraulic oil and shortening the oil change cycle

(3) the pressure oil discharged by the pump directly leads to the brake cylinder, and its pressure pulsation directly affects the balance of the working braking of the hoist, so the requirements for the pressure pulsation of the pump are strict

3 new hydraulic system for disc brakes

Figure 2 is a new hydraulic circuit for disc brakes. In this circuit, the electro-hydraulic proportional reducing valve 8 is used to replace the electro-hydraulic pressure regulating device 6 and overflow valve 7 in the original system to regulate the oil pressure in the brake cylinder during the working braking stage. In order to make the electro-hydraulic proportional reducing valve adjust the pressure quickly, its reducing valve structure is three-way, the accumulator 7 is used to maintain the pressure for the brake cylinder, and the unloading overflow valve 6 controls the loading and unloading of the oil pump

Figure 2 hydraulic system diagram of new hydraulic station

1 Oil tank 2 Electric contact pressure thermometer (wtz-228) 3 Type oil filter 4 Motor (yn=0.75kw) 5 Gear pump

6 Unloading overflow valve 62ya standby system (the same as the left figure) 7 Accumulator 8 Electrohydraulic proportional reducing valve 8 Electrohydraulic pressure regulating device

9 Manual directional valve 10 Pressure gauge 11 Secondary brake safety valve 12 Five way valve 13 Four way valve 14 Brake cylinder 15 Disc brake

the working process of the system is: during the rest time of the hoist, the pump 5 fills the accumulator 7 with oil. When the accumulator pressure rises to the maximum working pressure, the pressure oil opens the safety valve of the unloading overflow valve 6, the oil pump unloads, the rest time ends, the current of the electro-hydraulic pressure regulating device 8 is adjusted to the maximum, the electro-hydraulic proportional reducing valve 8 is in a non working state, the valve 11 is charged, and the oil of the accumulator is environmentally friendly through valve 8, valve 9 and valve 11 Energy saving is the key to development. Enter the brake cylinder 14, release the disc brake 15, and start the hoist. During the operation stage of the hoist, the pressure of the brake cylinder is maintained by the accumulator, so that the disc brake is released. In the working braking stage, the current in the electro-hydraulic pressure regulating device 8 decreases, the oil pressure in the brake cylinder decreases, the pressure oil in the cylinder flows back to the oil tank through the pressure reducing valve, and the disc brake generates braking torque and participates in the control of the hoist

4 effect comparison

in the hydraulic system of the new hydraulic station, the electro-hydraulic proportional reducing valve directly regulates the pressure of the brake cylinder, and the pressure pulsation of the pump does not affect the balance of the hoist in the braking stage, so the hoist runs more smoothly in this stage, and the cheaper gear pump can be used as the hydraulic pump

The displacement value is displayed on the computer screen. In the new system, the accumulator is used to maintain the pressure, and the oil pump is unloaded, so there is almost no overflow loss, which greatly reduces the power consumption of the pump station. Practice has proved that it can save 90% electricity compared with the original system

since the new system has almost no overflow loss, the system has less heating, low temperature rise and slow oil oxidation, which can reduce the size of the oil tank, prolong the oil change cycle of hydraulic oil and reduce the consumption of hydraulic oil. (end)

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