A radial piston pump is a piston pump in which the reciprocating direction of the piston or plunger is perpendicular to the drive shaft. Radial piston pumps have the advantages of low noise and high working pressure, but the piston pump is more sensitive to contamination of hydraulic oil and has a higher cost. Radial piston pumps are widely used in aircraft, hydraulic presses, engineering machinery and ships.

Radial piston pump types:

According to the flow distribution mode, radial piston pumps are generally divided into two types: axial flow and valve flow. Valve flow radial piston pumps have shortcomings such as high failure rate and low efficiency, while axial flow radial piston pumps overcome the shortcomings of valve flow radial piston pumps. Axial flow radial piston pumps are destined to be more impact resistant, longer life, and have higher control accuracy than axial piston pumps. The following are some common radial piston pumps:

1. High pressure radial piston pump;

2. Axial flow radial piston pump;

3. Valve-matched radial piston pump;

4. Load-sensitive variable radial piston pump, etc.

Radial piston pump performance parameters:

The main performance of the radial piston pump includes pressure, displacement, speed, efficiency and life, etc. The main structural parameters include the diameter and number of plungers, the inclination angle of the swash plate, etc.

① Pressure: Among radial piston pumps, the pressure of the valve distribution pump is relatively high, generally reaching more than 32MPa, and some products are even as high as 200MPa; the pressure of the axial distribution pump is generally more than 20MPa.

② Estimation and range of displacement: The displacement of a radial piston pump mainly depends on the diameter of the plunger, the effective stroke and eccentricity of the plunger, and the number of actions of each plunger in each working cycle.

③Rotation speed: The allowable speed of the radial piston pump is also very high, and the specific value varies depending on the displacement specifications.

④Efficiency: The volumetric efficiency and total efficiency of the radial piston pump are related to the working conditions of the pump.

⑤Service life: Under correct usage conditions (especially when using a working medium of appropriate viscosity and maintaining sufficient cleanliness), the service life of the radial piston pump is very long under rated working conditions.

⑥Flow pulsation and noise: Compared with gear pumps, vane pumps and screw pumps, the flow pulsation and noise of plunger pumps are larger.

Radial piston pump structure:

The radial piston pump is mainly composed of a stator, a rotor, a sleeve, an oil distribution shaft and a plunger. There is an eccentricity between the center of the rotor and the stator. The oil distribution shaft is fixed and has an oil distribution window along the circumference. The upper half of the oil distribution window corresponds to the oil suction port, and the lower half corresponds to the oil pressure port. The following is a schematic diagram of the radial piston pump structure:

Working principle of radial piston pump:

The driving torque is transmitted from the drive shaft to the star-shaped hydraulic cylinder rotor through the cross coupling, and the stator is not subject to other lateral forces. The rotor is mounted on the distribution shaft. A radially arranged plunger located in the rotor rests against the eccentric stroke stator via a hydrostatically balanced sliding shoe. The plunger is connected to the sliding shoe ball hinge and locked by a circlip. Two retaining rings hold the sliding shoe on the stroke stator.

When the pump rotates, it relies on centrifugal force and hydraulic pressure to press against the inner surface of the stator. When the rotor rotates, due to the eccentricity of the stator, the plunger will reciprocate, and its stroke is twice the eccentricity of the stator. The eccentricity of the stator can be adjusted by two radially opposite plungers on the pump body.

The inflow and outflow of oil passes through the flow channel on the pump body and the distribution shaft, and is controlled by the oil suction port on the distribution shaft. The hydraulic pressure generated in the pump body is absorbed by the surface of the static pressure balance. The static pressure balance of the friction pair adopts the overbalance pressure compensation method, forming an open-loop control. The bearing supporting the drive shaft only plays a supporting role and is not affected by other external forces.

Radial piston pump features:

1. The plungers are distributed radially, with large radial dimensions and small axial dimensions, making it easy to form a hydraulic pump-hydraulic motor unit.

2. The pressure does not need to be very high, the flow rate is large.

3. Changing the eccentricity can change the flow rate, and changing the direction of the eccentricity can change the direction of oil suction and discharge.

4. Without self-priming ability, a gear pump is often used to provide 0.5 MPa low-pressure oil to its inlet.

The difference between radial piston pump and axial piston pump:

1. The relative positions of the plunger and the power shaft are different. The reciprocating direction of the plunger of the axial piston pump is parallel to the direction of the central axis of the cylinder; the reciprocating direction of the plunger of the radial piston pump is perpendicular to the drive shaft.

2. The axial piston pump has the advantages of simple structure, small size, low noise, high efficiency, long life and self-priming ability. However, the structure is more complex than the radial piston pump and requires high processing and manufacturing requirements.

3. The radial piston pump has low noise, high working pressure, impact resistance, longer life and higher control accuracy than the axial piston pump; however, it also has the disadvantage of being more sensitive to contamination of hydraulic oil and having a higher cost.