Hydraulic motor

From the perspective of energy conversion, hydraulic pumps and hydraulic motors are hydraulic components that work reversibly. Inputting working fluid to any hydraulic pump can turn it into a hydraulic motor working condition; on the contrary, when the main shaft of the hydraulic motor is external When the torque is driven to rotate, it can also be changed to the working condition of the hydraulic pump. Because they have the same basic structural elements-airtight but cyclically variable volume and corresponding oil distribution mechanism.

1. What is a hydraulic motor

The hydraulic motor is an executive component of the hydraulic system. It converts the hydraulic pressure energy provided by the hydraulic pump into the mechanical energy (torque and speed) of its output shaft. Hydraulic motors, also known as oil motors, are mainly used in injection molding machinery, ships, hoists, construction machinery, construction machinery, coal mining machinery, mining machinery, metallurgical machinery, ship machinery, petrochemicals, port machinery, etc.

2. Working principle of hydraulic motor

The characteristics and classification of hydraulic motors A hydraulic motor is a device that converts the pressure energy of a liquid into mechanical energy. In principle, a hydraulic pump can be used as a hydraulic motor, and a hydraulic motor can also be used as a hydraulic pump. But in fact, although the same type of hydraulic pump and hydraulic motor are similar in structure, due to the different working conditions of the two, there are some differences in the structure of the two. E.g:

1. Hydraulic motors generally need forward and reverse rotations, so they should have symmetry in the internal structure, while hydraulic pumps generally rotate in one direction, so there is no such requirement.

2. In order to reduce the oil suction resistance and radial force, the oil suction port of the hydraulic pump is generally larger in size than the oil outlet. The pressure in the low pressure chamber of the hydraulic motor is slightly higher than the atmospheric pressure, so there is no such requirement.

3. The hydraulic motor is required to work normally in a wide range of speed. Therefore, hydraulic bearings or hydrostatic bearings should be used. Because when the motor speed is very low, it is difficult to form a lubricating sliding film if a dynamic pressure bearing is used.

4. The vane pump relies on the centrifugal force generated by the high-speed rotation of the vane and the rotor to make the vane always close to the inner surface of the stator to seal the oil and form a working volume. If it is used as a motor, a spring must be installed at the root of the blade of the hydraulic motor to ensure that the blade is always close to the inner surface of the stator so that the motor can start normally.

5. The structure of the hydraulic pump needs to ensure that it has the self-priming ability, but the hydraulic motor does not have this requirement.

6. The hydraulic motor must have a large starting torque. The so-called starting torque is the torque that can be output on the motor shaft when the motor is started from a stationary state. The torque is usually greater than the torque in the running state at the same working pressure difference. Therefore, in order to make the starting torque as close as possible to the working state The torque of the motor requires small pulsation of the motor torque and small internal friction.Due to the above-mentioned different characteristics of hydraulic motors and hydraulic pumps, many types of hydraulic motors and hydraulic pumps cannot be used in reverse.

3. The role of hydraulic motors

Mainly used in injection molding machinery, ships, hoists, construction machinery, construction machinery, coal mining machinery, mining machinery, metallurgical machinery, ship machinery, petrochemicals, port machinery, etc.

The high-speed motor gear motor has the advantages of small size, light weight, simple structure, good manufacturability, insensitivity to oil pollution, impact resistance and low inertia. Disadvantages include large torque pulsation, low efficiency, low starting torque (only 60%-70% of rated torque) and poor low-speed stability.