Classification and working principle characteristics of hydraulic system device plunger pump

The plunger pump is an important device in the hydraulic system. It relies on the reciprocating movement of the plunger in the cylinder to change the volume of the sealed chamber to achieve oil absorption and oil pressure. The plunger pump has the advantages of high rated pressure, compact structure, high efficiency, and convenient flow adjustment. Piston pumps are widely used in high pressure, large flow and flow regulation, such as hydraulic presses, engineering machinery and ships.

First, the classification of plunger pump

Piston pumps are generally divided into single plunger pumps, horizontal plunger pumps, axial plunger pumps and radial plunger pumps.

1. Single plunger pump

The main structure is composed of eccentric wheel, plunger, spring, cylinder and two check valves. A sealed volume is formed between the plunger and the cylinder bore. When the eccentric wheel rotates, the plunger reciprocates up and down once, sucking oil downwards and discharging oil upwards. The amount of oil pumped out per revolution is called the displacement, and the displacement is only related to the structural parameters of the pump.

2. Horizontal plunger pump

The horizontal plunger pump is a hydraulic pump in which several plungers (generally 3 or 6) are installed side by side, and the crankshaft directly pushes the plunger to reciprocate through the connecting rod slider or eccentric shaft to realize suction and discharge. They also use valve-type dispensing devices, and most are used with metering pumps. The emulsion pump in coal mine hydraulic support system generally adopts horizontal plunger pump. Emulsion pump is used in coal mining face to provide emulsion for hydraulic supports. Its working principle is to rely on the rotation of the crankshaft to drive the piston to do reciprocating motion to realize the suction of liquid.

3. Axial type

An axial piston pump is a pump in which the piston or plunger reciprocates in a direction parallel to the central axis of the cylinder. Axial piston pumps work by using the volume change caused by the reciprocating motion of the piston in the plunger hole parallel to the drive shaft. Since both the plunger and the plunger hole are circular parts, high-precision fit can be achieved, resulting in high volumetric efficiency.

4. Straight axis swash plate

Straight axis swash plate plunger pumps are divided into pressure oil supply type and self-priming type. The pressure oil supply hydraulic pump is mainly supplied by the hydraulic cylinder with air pressure, and the hydraulic cylinder is supplied with air pressure. After starting the machine every time, it is necessary to wait for the hydraulic cylinder to supply oil with air pressure before operating the machine. If the pressure of the hydraulic cylinder is not enough to start the machine, the hydraulic pump will cause a pull-off phenomenon in the sliding shoe, which will cause abnormal wear of the return plate and pressure plate of the pump body.

5. Radial formula

Radial piston pumps can be divided into two categories: valve distribution and shaft distribution. Valve-matched radial piston pump has high failure rate and high efficiency

6. Hydraulic

The hydraulic plunger pump is driven by the air pressure oil tank. After starting the machine each time, the machine must wait for the air pressure of the hydraulic oil tank to be used before running the machine. Straight axis swash plate plunger pumps are divided into pressure oil supply type and self-priming type. The pressure oil supply hydraulic pump mainly uses a pneumatic oil tank, and the hydraulic pump itself has a charge pump to provide pressure oil to the inlet of the hydraulic pump. The self-priming hydraulic pump has a strong self-priming ability and does not require external oil supply.

The axial-flow radial piston pump developed in the 1970s and 1980s overcomes the problem of insufficient valve position distribution of the radial piston pump. Due to the characteristics of the radial pump structure, the radial distribution radial piston pump has fixed impact resistance, longer service life and higher control precision than the axial piston pump. Under the action of the variable plunger and the limit plunger, the variable control of the variable stroke short pump is realized by changing the eccentricity of the stator. The determined eccentricity is 5-9mm (according to different displacements), and the variable stroke is very short. The variable mechanism is designed for high pressure operation and is controlled by a control valve. Therefore, the response speed of the pump is fast. The radial structure design overcomes the problem of eccentric wear of sliding shoes such as axial piston pumps. Thereby greatly improving its impact resistance.

The pressure oil pump body of the variable plunger pump, the oil hole of the pump casing enters the lower chamber of the variable casing through the check valve, when the rod moves downward, the servo piston moves downward, pushing the valve port of the servo valve to open, and the pressure of the oil in the lower chamber Variable variable piston cavity shell on variable shell oil hole.