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Piston Hydraulic motor working principle

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Author : Peter
Update time : 2019-10-08 21:36:13
Hydraulic motor working principle
First, 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. However, in fact, the same type of hydraulic pump and hydraulic motor are structurally similar, but 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 to be so there should be symmetry in the internal structure, and the hydraulic pump is generally unidirectional, there is no such requirement.
2. In order to reduce the oil absorption resistance and reduce the radial force, the suction port of the general hydraulic pump is larger than the size of 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. Hydraulic motors are required to operate normally over a wide range of speeds. Therefore, hydraulic or hydrostatic bearings should be used. Because when the motor speed is very low, if a dynamic pressure bearing is used, it is difficult to form a lubricating slip film.
4. The vane pump relies on the centrifugal force generated by the high speed rotation of the vane and the rotor so that the vane always adheres to the inner surface of the stator.
It acts as a sealing oil to form a working volume. If it is used as a motor, a spring must be attached to the blade root of the hydraulic motor to ensure that the blade is always in close contact with the inner surface of the stator so that the motor can start normally.
5. The hydraulic pump must be self-priming in terms of construction, and 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 standstill state. This torque is usually greater than the torque in the running state when the same working pressure difference is used.
In order to make the starting torque as close as possible to the torque in the operating state, the pulsation of the motor torque is required to be small, and the internal friction is small.
Since the hydraulic motor and the hydraulic pump have the above different characteristics, many types of hydraulic motors and hydraulic pumps cannot be used interchangeably.
The hydraulic motor is divided into two categories according to its rated speed: high speed and low speed. The rated speed is higher than 500r/min, which belongs to high speed hydraulic motor. The rated speed is lower than 500r/min.
The basic types of high-speed hydraulic motors are gear, screw, vane and axial piston. Their main features are high speed, small moment of inertia, easy start and brake, high sensitivity for speed regulation and commutation. Usually, the high-speed hydraulic motor has a small output torque (only a few tens of kilometers to several hundred cows per meter), so it is also called a high-speed small torque hydraulic motor.
The basic type of high-speed hydraulic motor is radial piston type, such as single-acting crankshaft linkage, hydraulic balance and multi-acting inner curve. In addition, there are also low-speed structural types in the axial piston type, vane type and gear type. The main features of the low-speed hydraulic motor are large displacement, large volume, low speed (sometimes up to a few turns per minute or even a few rpm), so it can be directly connected to the working mechanism without the need for a reduction gear, which greatly simplifies the transmission mechanism. Usually, the low-speed hydraulic motor has a large output torque (up to several thousand Newton-meters to tens of thousands of Newtons-meters), so it is also called a low-speed high-torque hydraulic motor.
Hydraulic motors can also be divided according to their construction type, which can be divided into gear type, vane type, plunger type and other types.