Features of QJM Hydraulic Motor

The QJM series hydraulic motor can be combined with various oil pumps, valves, and hydraulic accessories to form a hydraulic rotation device, which is adaptable to a wide range of mechanical working conditions. This hydraulic motor boasts a series of advantages, including light weight, compact size, wide speed regulation range, excellent low-speed stability, reliable operation, impact resistance, high efficiency, and long service life. Its main features are as follows:

The rolling element of this motor uses a single steel ball instead of the two or more rollers and crossbeams used in conventional internal-curve hydraulic motors. As a result, it features a simple structure, reliable operation, compact size, and light weight.

With a small moment of inertia and a robust, reliable steel ball, the motor can operate continuously under impact loads.

It has low friction: the oil distribution shaft and rotor are internally balanced; the ball-plunger pair transmits force through a ball pad made of self-lubricating composite material, with hydrostatic balance and good lubrication conditions. A soft plastic piston ring that automatically compensates for wear is used to seal high-pressure oil. Thus, the motor achieves high mechanical and volumetric efficiency, can operate stably at extremely low speeds, and delivers a large starting torque.

Due to its structural characteristics, the motor requires a relatively low return oil backpressure (generally 0.3–0.8 MPa). The higher the rotational speed, the greater the required backpressure.

This motor is available with two-speed and three-speed displacement control, providing a wide speed regulation range.

It has a simple structure, enabling easy disassembly and maintenance. There are no special requirements for oil cleanliness, and the oil filtration precision can be selected according to the requirements of the matched oil pump.

Internal-Curve Motor: Types and Working Principle

Internal-curve motors come in various configurations. Among them, shaft-rotating, housing-rotating, and other types are classified based on their application methods; there are also multiple types categorized by the product’s transmission method and plunger component structure. However, despite the different types of oil motors, their working processes are similar.

Working Principle of Internal-Curve Motors

During operation, hydraulic oil is distributed to the oil chambers at the bottom of the plungers in the working section through the oil distribution ports on the oil distribution shaft. The pressure oil pushes the rollers of the plunger assembly to press tightly against the surface of the guide rail. At the contact point, the guide rail exerts a reverse reaction force N on the rollers, which acts perpendicular to the surface of the guide rail and passes through the center of the rollers.

This force can be resolved into two components: a component P along the axial direction of the plunger, and a component T perpendicular to the centerline of the plunger. The high-torque hydraulic motor transmits this force to the cylinder block through the side of the load beam, generating torque on the cylinder block. When the oil inlet and outlet ports are swapped, the motor rotates in the reverse direction.