Created on:2021-10-21 14:02

Railway engineering equipment_ Overview of hydraulic system of tamping truck

Railway engineering equipment_ Overview of hydraulic system of tamping truck

(1) Overview of hydraulic system of tamping truck

Tamping car is a large-scale railway maintenance machinery and equipment. It is used in the construction of new railway lines, large-scale screening operation of old lines and line maintenance. The tamping truck shall carry out track shifting, track lifting and leveling, ballast tamping of track bed and ballast tamping of track bed. After the tamping car is used, the track direction, left and right horizontal height difference and front and rear height can meet the requirements of the standards required in the line design and the requirements of the line maintenance rules. The tamping device is the main actuator of the tamping vehicle, which is used for tamping the track bed, so as to ensure the stability of the track bed. Hydraulic system is an important part of tamping device.

Taking 08-32 tamping truck as an example, it is equipped with left and right tamping devices in the car body, which can tamp the ballast on the track bed at the same time or work with a separate tamping device. During the operation of the tamping device, the insertion depth, clamping time and clamping force are adjusted according to the construction requirements. During the tamping operation, the rammer can be selected to tamp the ballast on both sides according to the needs. When it is necessary to use the rammer to cooperate with the tamping device, the lifting cylinder of the rammer and the lifting cylinder of the tamping device act synchronously; The transverse cylinder of the tamping device acts at any time according to the line conditions.

In addition to vibration, the clamping and lifting cylinders of the tamping device work intermittently. During tamping operation, the basic action procedure of the hydraulic cylinder is: after the lifting hydraulic cylinder makes the tamping pick insert into the track bed to a certain depth, the clamping hydraulic cylinder acts. After the clamping is completed, the lifting hydraulic cylinder raises the tamping device. At the same time, the clamping hydraulic cylinder acts to open the internal and external tamping picks for the next tamping.

(2) Composition and function of hydraulic system

The hydraulic circuit of left and right tamping devices of 08-32 tamping machine is shown in Figure C., The lifting, traverse and clamping hydraulic cylinders are supplied by three circuits with different pressures, which can be divided into several independent hydraulic circuits.

C.jpg

① The pressure of the hydraulic circuit of the outer clamping hydraulic cylinder is 15MPa. The oil circuits of the four outer clamping hydraulic cylinders on one side of the tamping device are connected in parallel, and the large chamber and small chamber oil circuits of the hydraulic cylinder are controlled by two electromagnetic directional valves 2 and 12 respectively. The oil circuit leading to the small cavity of the outer clamping hydraulic cylinder is equipped with two position four-way 12 and one-way throttle valve 13. In the initial position, the 15MPa pressure oil circuit is connected to the small cavity of the hydraulic cylinder. A two position four-way solenoid directional valve 2 and a one-way pressure reducing valve 11 are installed on the oil circuit leading to the large cavity of the outer clamping hydraulic cylinder, and the initial oil circuit is connected to the oil tank. When the electromagnetic directional valve does not act, the pressure oil in the small chamber of the hydraulic cylinder retracts the piston and the tamping pick is open.

When the outer clamping hydraulic cylinder acts, the solenoid valve 2 is powered on and reversed, and the 15MPa pressure oil is depressurized to 9 ~ 12.5mpa through the one-way pressure reducing valve and enters the large chamber of the hydraulic cylinder. At this time, although the large and small cavities of the hydraulic cylinder have pressure oil, the force at the large cavity end of the piston is greater than that at the small cavity end. The piston extends and the tamping device performs clamping action. When the electromagnetic reversing valve 12 reverses, the oil circuit in the small chamber of the hydraulic cylinder is cut off, and the clamping action of the outer clamping hydraulic cylinder cannot be carried out. At this time, only the clamping action of the inner clamping hydraulic cylinder can be realized, that is, the clamping and tamping operation on one side can be realized.

On the oil inlet path of the small cavity of the outer clamping hydraulic cylinder, the one-way throttle valve 13 is used to change the return oil flow of the small cavity of the hydraulic cylinder, so as to change the clamping action speed of the outer clamping hydraulic cylinder. The large chamber oil circuit of the outer clamping hydraulic cylinder is equipped with edge valve 18 and pressure relay 19 to detect the oil pressure during clamping action. When the oil pressure reaches the set value of the pressure relay, the pressure relay acts to provide the clamping end electrical signal to the control system of automatic circulation in the tamping process.

② The four inner clamping hydraulic cylinders of the tamping device on one side of the hydraulic circuit of the inner clamping hydraulic cylinder are connected in parallel, and the large and small cavities of the hydraulic cylinder are supplied by high and low pressure hydraulic pumps respectively. The large chamber of the hydraulic cylinder is connected with 4.5MPa pressure oil, and the small chamber is connected with 14MPa pressure oil through the directional valve 10.

The initial position of directional valve 10 allows the small chamber of the hydraulic cylinder to pass through the oil tank. When the valve does not act, there is 4.5MPa pressure oil in the large cavity of the inner clamping hydraulic cylinder, the piston extends, and the tamping pick is open. The reversing valve 10 reverses, the high-pressure oil enters the small chamber of the hydraulic cylinder, the force acting on the small chamber end of the piston of the inner hydraulic cylinder is greater than the force at the large chamber end, the piston rod retracts and clamps the hydraulic cylinder for clamping operation. The two 15 are used to absorb pressure pulsation and hydraulic shock. At the same time, it also has the function of oil supplement and pressure maintenance.

③ The transverse hydraulic circuit of the tamping device the transverse hydraulic cylinder 9 of the tamping device is controlled by the reversing valve 5, and the large and small cavity oil circuits of the hydraulic cylinder are equipped with a fixed throttle and a hydraulic lock 4. When valve 5 does not act, the large and small oil chambers of the hydraulic cylinder are closed by the hydraulic lock, and the piston is in a fixed position and does not move; When valve 5 acts, the pressure oil pushes the hydraulic lock open, communicates the large and small cavity oil circuits of the hydraulic cylinder, and the piston rod moves. The traverse speed of the tamping device is low, so a fixed throttle valve is installed on the inlet and outlet oil circuit of the hydraulic cylinder to limit the flow and reduce the action speed of the traverse hydraulic cylinder.

④ The left and right tampers of the rammer lifting hydraulic circuit have two lifting hydraulic cylinders 7 respectively. The two lifting hydraulic cylinders adopt parallel oil circuit and are controlled by three position four-way solenoid directional valve 3. The large chamber oil circuit of the hydraulic cylinder is equipped with a one-way throttle valve 8, which can adjust the oil inlet of the hydraulic cylinder and change the falling speed of the compactor.

⑤ The lifting hydraulic circuit of tamping device adopts electro-hydraulic position servo control, which has the characteristics of high position control accuracy and convenient adjustment of tamping pick insertion depth. Lifting hydraulic cylinder 14 is controlled by proportional directional valve 1. The circuit pressure oil is 14MPa, and the proportion control requires high oil cleanliness, so high pressure filter 6 is installed. The tamping electro-hydraulic position control system is composed of electro-hydraulic proportional directional valve, electronic amplifier, setting potentiometer, position sensor and lifting hydraulic cylinder. Its principle is shown in Figure D.

When the tamping device descends, the position sensor 4 changes the descending position into an electrical signal and inputs it into the electronic amplifier 2 for comparison with the signal of the set potentiometer. After amplification, the deviation signal is input into the proportional electromagnet B of the electro-hydraulic proportional directional valve 1. The proportional valve outputs the pressure oil flow proportional to the input electrical signal into the lifting cylinder to push the piston down.

As the insertion depth of the tamping device approaches the set depth, the deviation signal gradually decreases to zero and returns to zero. At this time, the output flow is also zero, and the lifting cylinder stops acting.

After the clamping action of the tamping device is completed, the amplifier inputs a certain electrical signal to the proportional electromagnet a of the electro-hydraulic proportional reversing valve 1, the proportional valve reverses, the hydraulic pressure enters the small cavity of the lifting hydraulic cylinder, and the tamping device rises to the set height.

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