Created on:2021-04-13 09:34

variable (speed regulation) principle and method

1.7.8 variable (speed regulation) principle and method

(1) Basic principle of variable speed and theoretical torque of hydraulic motor are respectively


It can be seen that the basic principle of hydraulic motor variable (speed regulation) is: by changing the theoretical flow port of hydraulic motor. Or changing the theoretical displacement V of the hydraulic motor itself can adjust the speed of the hydraulic motor.

When the inlet and outlet pressure difference △ P is fixed, changing the theoretical flow can only adjust the speed, but not the torque; if changing the theoretical displacement V, the torque can be adjusted, so as to keep the output power of the hydraulic motor constant.

(2) Variable method

① There are three ways to realize speed regulation by changing the flow QT of hydraulic motor.

a. Throttling speed regulation: oil is supplied by quantitative pump, and the flow control valve (throttling valve or speed regulating valve) is used to change the input flow of hydraulic motor (Fig. b).

b. Volume speed regulation: variable pump is used to supply oil and change the input flow of hydraulic motor (Fig. C).

c. Step volume speed regulation: use multiple quantitative pumps to supply oil, and change the input flow of hydraulic motor step by step through the combination of pump start and stop (Figure d).


② There are two ways to change the theoretical displacement V of hydraulic motor to realize speed regulation.

a. Stepless variable: such as stepless change of the inclination angle of the swash plate or cylinder block of the axial piston motor, thus continuously stepless change of the displacement.

b. Step variable: such as changing the number of action times of inner curve motor, the number of plunger or the number of plunger rows, so as to change the displacement step by step.

The specific structure of changing the theoretical flow rate and stepless displacement of the hydraulic motor varies with the structure of the motor.

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