1、 Characteristics and categories of hydraulic motors

From the perspective of energy conversion, the hydraulic motor converts the input hydraulic energy into mechanical kinetic energy, while the hydraulic pump is just different. Therefore, the hydraulic pump and the hydraulic motor are hydraulic components for reversible operation. Feeding operating fluid to any hydraulic pump can make it become the working condition of the hydraulic motor; Conversely, when the main shaft bearing of the hydraulic motor rotates from the external torque, it can also become the working condition of the hydraulic oil pump. Because they have the same basic structural factors - sealed and periodically changeable volume and corresponding oil distribution structure.

However, in view of the different operating conditions of hydraulic motors and hydraulic oil pumps, the requirements for their performance indicators are also different, so there are still many differences between similar hydraulic motors and hydraulic oil pumps. The main hydraulic motor should be able to rotate in both positive and negative directions, so its internal structural symmetry is required; The rotating speed range of the hydraulic motor must be very large, especially for its extremely low and stable rotating speed. For this reason, it generally adopts roller bearings or hydrostatic rolling bearings; In addition, since the hydraulic motor works under the condition of feeding pressure oil, it does not need to have self-priming function, but must have corresponding initial sealing performance to give the necessary starting torque. In view of this difference, the hydraulic motor and hydraulic oil pump are similar in structure, but can not operate reversibly.

Hydraulic motors can be divided into transmission gear type, vane type, plunger type and other types according to their structural types. According to the rated rotation speed of the hydraulic motor, it can be divided into two categories: high speed and low speed. Rated speed higher than 500 r/min belongs to High speed hydraulic motor , rated speed less than 500 r/min belongs to Low speed hydraulic motor 。 The basic types of high-speed hydraulic motors include transmission gear type, screw type, vane type and axial plunger type. The main characteristics between them are high rotation speed, small inertia moment, convenient starting and braking, and high sensitivity of adjustment (speed change and reversing). Generally, the output torque of high-speed hydraulic motor is not large (only tens of N · m to hundreds of N · m), so it is also called high-speed small torque hydraulic motor. The basic types of low-speed hydraulic motors are radial plunger type and cycloidal type. The main characteristics of low-speed hydraulic motors are large oil discharge and low rotation speed. Therefore, they can be immediately connected with the operating structure, without speed reducer, which makes the transmission mechanism greatly simplified. Generally, the output torque of low-speed hydraulic motors is relatively large (up to thousands of N · m), Therefore, it is also called low-speed large torque hydraulic motor.

2、 Basic operating principle

Cycloidal hydraulic motor is a kind of hydraulic motor Planetary reducer Internal toothing made of similar basic working principles (basic working principles of small gear difference) Cycloidal gear hydraulic motor , referred to as cycloidal hydraulic motor for short.

For example, the motor rotor and the motor stator are a pair of cycloid tooth needle tooth pairs. The motor rotor has a short amplitude external cycloid pitch line tooth type of Zi (Zi=6 or 8) teeth, the motor stator has a Zi+1 arc tooth needle tooth type, and the motor rotor and motor stator become a Zi+1 closed gear volume. Most of them are in high pressure areas and most of them are in low pressure areas. The stator of the motor is fixed, the middle of the gear is 02, and the middle of the motor rotor is Oi. The hydraulic torque formed by the motor rotor under the effect of pressure oil moves around the middle 02 of the motor stator with the radius of eccentricity g. That is, when the motor rotor rotates around its middle Oi, on the other hand, its middle Oi rotates in the opposite direction around the middle 02 of the motor stator. When the motor rotor rolls along the motor stator, its inlet and outlet oil cavities change constantly, However, it has been divided into two sides with the junction line Oi02 as the boundary, one side is the oil inlet, and the capacity of the chamber is gradually expanded; At the same time, the oil is drained, and the capacity is gradually reduced. The hydraulic oil is squeezed out Oil motor The oil drain is discharged to the hydraulic oil tank.