Product Features

The YMS hydraulic motor is an internal-curve, multi-acting radial piston motor. Its main features are as follows:

Modular Design: The overall structure adopts a modular design with a chip-type stacking configuration. It is divided into four parts: the mechanical output module, hydraulic function module, flow distribution module, and mechanical braking module. This design facilitates compatibility with various mainstream optimized supporting systems.

High Efficiency: It adopts flat valve flow distribution technology, which has low sensitivity to pressure and temperature. This technology automatically compensates for wear between the flow distribution friction pairs, ensuring the motor maintains high volumetric efficiency for a long time. Meanwhile, the adoption of a roller-plunger structure simplifies the force transmission mechanism and improves mechanical efficiency.

High Operating Pressure and Excellent Low-Speed Performance: The stator curve design has been optimized to ensure output torque and stable rotational speed while reducing stator contact stress. Additionally, the stator is manufactured using new materials and advanced processes, significantly increasing the hydraulic motor’s operating pressure—with a maximum pressure of up to 40 MPa. Owing to the low inertia of the force transmission mechanism, the plunger pair equipped with a sealing piston ring, and the roller stopper made of anti-friction material, the motor achieves high starting efficiency and excellent low-speed performance.

Capability to Withstand Radial and Axial Loads: With an independently configured mechanical output module, as well as a large-diameter output shaft and bearings, the motor can withstand large axial and radial forces. It can be directly connected to a gear output or installed directly on the drive wheel of a vehicle.

Optional Mechanical Brake: It adopts a modular chip-type structure, allowing the integration of a mechanical braking device to achieve direct and safe service braking and parking braking of the output shaft.

Motor Displacement Control: Motors are available in two types: single-displacement motors and double-displacement motors. Single-displacement motors output full displacement, while double-displacement motors can switch between full-displacement and half-displacement output via control valve regulation to achieve speed control.

Radial Piston Hydraulic Motor

The working principle of the radial piston hydraulic motor is as follows: When pressure oil enters the bottom of the piston inside the cylinder block through the port of the fixed oil distribution shaft (4), the piston extends outward and tightly presses against the inner cavity of the stator—this is because there is an eccentricity between the stator and the cylinder block. At the contact point between the piston and the stator, the stator exerts a reaction force on the piston. This force can be resolved into two component forces. Given that the hydraulic oil pressure at the bottom of the piston is p and the piston diameter is d, when the angle between the force and the center (axis) is x, the force generates a torque on the cylinder block, causing the cylinder block to rotate. The cylinder block then outputs torque and rotational speed outward through the rotating shaft connected to its end face.

The above analysis describes the torque generated by a single piston in the hydraulic motor. In a Hagglunds hydraulic motor, since multiple pistons act in the pressure oil zone, the torques generated by all these pistons collectively drive the cylinder block to rotate and output torque. Radial piston hydraulic motors are mostly used in scenarios requiring low speed and high torque.