Created on:2021-06-05 10:00

Performance parameters of swing hydraulic motor

Performance parameters of swing hydraulic motor

The performance parameters of swing hydraulic motor mainly include pressure, torque, efficiency, angular velocity and angle.

(l) At present, the working pressure of vane swing hydraulic motor is generally not more than 32 MPa.

(2) The output torque, angular velocity, efficiency torque and angular velocity are the main performance parameters of the swing hydraulic motor, and the calculation formula varies with the structure type. Table 6-7 gives the calculation formulas of output torque and return angle speed of vane type and piston type swing hydraulic motors.

Technical formula of output torque and angular velocity of swing hydraulic motor

Motor type

Output shaft torque T / N · M

Angular velocity of gyration ω / rad · S-1


Vane type



/(D2-d2)Zb] ×10-4

P1 - inlet pressure, PA;

P2 - pressure of oil discharge, PA;

Q - input flow, L / min;

Z-number of blades;

D-inner diameter of cylinder block, m;

D - outer diameter of blade mounting shaft, inner diameter of small cylinder block (chain type), piston diameter (reciprocating), m;

B - blade axial width, m;

DG - gear indexing element diameter (rack and pinion type), screw pitch diameter (piston screw type), sprocket pitch diameter (chain type), m;

λ - helix angle, RAD;

ρ - equivalent friction angle, RAD;

T-pitch, m;

I - crank length, m;

S-crank length, m;

η m - mechanical efficiency of motor, single blade type η M = 80% ~ 90%, multi blade type even 90% ~ 95%, piston type η M = 80%;

η V - volumetric efficiency, single blade type is η v = 90-95, multi blade type is usually less than 90%, piston type efficiency is almost 100%

Piston type






T=1/8πDgD2(p1-p2) ηm








tan(λ-ρ)(p1-p2) ηm


/[t(D2-d2) ]×10-4





T=1/8πDg(D2-d2)(p1-p2) ηm


/[Dg(D2-d2)] ×10-4






T=1/4πID2(p1-p2) ηm

ω=2/3×qηv/(πID2) ×10-4




T=1/8S(D2-d2)(p1-p2) ηm


/[S(D2-d2)] ×10-4


In all kinds of swing hydraulic motors, the volume leakage is all internal leakage, which mainly depends on the structure of the seal and the selection of the seal material. It also plays a decisive role in the mechanical friction loss, starting characteristics and low speed stability of the motor. The mechanical efficiency of the vane type swing motor is higher than that of the piston type swing motor, while the internal leakage of the piston type swing motor is very small, and its volumetric efficiency is higher than that of the vane type swing motor. The efficiency range of various motors is shown in table 6-7.

The output torque of single blade swing hydraulic motor is not more than 35000 n · m, and that of multi blade swing hydraulic motor is not more than 83000 n · M.

The output torque of piston rack and pinion swing hydraulic motor can reach more than 1000000 N.M.

The angular velocity of various swing hydraulic motors is usually not greater than 100 ° / s.

(3) The maximum angle of single blade swing motor is not more than 310 ° and that of multi blade swing motor is not more than 100 °.

In the piston swing motor, the angle of rack and pinion type and piston screw type motor can be selected freely by controlling the piston stroke, and the angle can be greater than 360 ° if necessary; the angle of compound swing motor can be obtained by controlling the lead of compound screw pair, and greater than 360 ° if necessary. The maximum angle of the chain swing motor is not more than 90 degrees.


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