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MDP Hydraulics
The low-noise lightweight hydraulic five-star motor is a low-speed high-torque hydraulic actuating element designed based on the radial piston and five-star wheel (crankshaft connecting rod) principle. It is specifically optimized for hydraulic systems that require smooth, powerful, compact, and quiet power output. Through the adoption of a low vibration frequency structure with five eccentric pistons in the crankshaft, lightweight high-strength materials, and precise friction pair design, this motor maintains the core advantages of traditional radial piston motors such as high starting torque and excellent low-speed stability while significantly reducing operating noise and weight. It is widely used in the rotation, movement, and lifting drive systems of construction machinery, mining equipment, ship deck machinery, plastic machinery, etc., and is a key power component for achieving efficient, reliable, and quiet operation of equipment.
The five-star motor is a radial piston hydraulic motor. Its core working principle is as follows: Pressurized oil flows orderly into the piston cylinders arranged in a five-star shape radially through the distribution shaft (or distribution disc). The high-pressure oil pushes the pistons to move outward. The pistons, through connecting rods or directly acting on the eccentric crankshaft, generate tangential forces, thereby driving the crankshaft (i.e., the output shaft) to rotate and converting the hydraulic energy into mechanical torque for output. The oil that has completed the work flows back to the oil tank from the other side. By changing the direction of oil intake, the motor can achieve forward and reverse rotation.
Its "low noise" and "lightweight" features are derived from the following core structural design:
Low noise design: Utilizing a five-piston eccentric crankshaft structure, its inherently lower excitation frequency can effectively disperse and counteract pressure pulsations, reducing vibration and noise at the source. The key friction pairs (such as between the crankshaft and the connecting rod) are supported by ball bearings, minimizing mechanical friction and impact sounds.
Lightweight design: The shell is made of high-strength aluminum alloy or precision cast ductile iron, which ensures structural strength while minimizing weight to the greatest extent. The compact radial layout and optimized internal channels achieve a high power-to-weight ratio (higher specific power).
The five-plunger eccentric structure combined with precise planar compensation flow distribution technology results in small torque pulsation and low vibration, making it particularly suitable for indoor equipment or precision machinery with strict requirements for working environment noise.
The mechanical efficiency at startup is high (up to 0.92 or above), enabling smooth operation at extremely low speeds (even lower than 1 r/min). The speed adjustment range is wide, allowing direct drive of large inertia loads, without or with only a small reduction mechanism.
As a radial piston motor, it has strong pressure-bearing capacity, with the rated working pressure typically reaching 20-31.5 MPa, and the maximum pressure up to 35-45 MPa, capable of providing huge output torque. Advanced seals such as sealing rings are used, with a volumetric efficiency of up to 95%-97% or more.
The radial layout and optimized design make it smaller in volume and lighter in weight compared to other designs, facilitating integration and installation in equipment with limited space.
Key components use special heat treatment and wear-resistant materials, with roller bearings providing high mechanical efficiency and low wear. The structure is sturdy, capable of withstanding certain radial and axial external forces, suitable for harsh conditions, and has a long design service life.
With its low-speed high-torque, stable and reliable performance, as well as compact structure, this motor is suitable for numerous heavy-duty and precision driving applications:
• Construction machinery: the rotating mechanisms of excavators and loaders; the drum drive of concrete mixer trucks.
• Mining machinery: Rock drilling truck arm rotation, coal mine transportation machine, crusher.
• Ship machinery: Deck machinery such as winches, anchor winches, steering gear, and hatch opening/closing devices.
• Plastic machinery: Solvent for injection molding machines, mold clamping drive.
• Metallurgy and Heavy Equipment: Auxiliary drive systems for rolling mills, furnace tilting devices for metallurgical furnaces.
• Others: Wind turbine yaw braking, geological drilling equipment, large valves opening and closing.
Correct selection is the key to ensuring system compatibility and performance:
1. Determine the load torque and speed: Based on the maximum working torque required by the equipment and the common speed range, combined with the system working pressure, use the formula Torque (N.m) ≈ 0.159 × Working pressure difference (MPa) × Displacement (ml/r) × Mechanical efficiency to initially calculate the required displacement.
2. Match system pressure: The rated pressure and maximum pressure of the selected motor must be higher than the maximum working pressure and peak pressure of the hydraulic system.
3. Evaluate installation space and interfaces: Based on the equipment layout, determine the installation method of the motor (flange or stand), the form of the output shaft (keyway type), as well as the size and position of the oil ports.
4. Consider special requirements: Clearly define special requirements such as noise level, weight limit, protection level (IP), and whether it needs to operate in free-wheeling conditions.
5. Consult the supplier: Provide detailed operating parameters (pressure, flow rate, load curve, environmental temperature, etc.), and have professional technicians recommend the most suitable model and configuration.
• Oil requirements: Clean anti-wear hydraulic oil must be used. The recommended viscosity range is 30-50 cSt, and the cleanliness grade should be no less than NAS 9. Appropriate precision filters (recommended 25μm) must be installed at the inlet and outlet oil ports.
• Installation requirements: Ensure that the output shaft of the motor is perfectly concentric with the drive shaft to avoid excessive additional radial force. The oil drain pipe must be connected directly and unobstructedly back to the oil tank, and the highest point of the connection should be higher than the motor housing. The back pressure of the housing usually should not exceed 0.1 MPa.
• Startup and Operation: For the first start-up or after a long period of shutdown, fill the motor housing with hydraulic oil and perform exhaust. It is recommended to start the machine under no-load or low-load conditions, and then gradually increase the load.
• Maintenance: Regularly check the tightness of the connecting bolts, as well as for any leakage at the shaft seals and interfaces. Replace the hydraulic oil and filter elements according to the equipment maintenance schedule. If there is insufficient output, abnormal noise, overheating or leakage, the machine should be immediately shut down for inspection of system pressure, oil cleanliness and motor condition.
The low-noise lightweight hydraulic five-star motor represents the advanced direction of low-speed high-torque hydraulic drive technology. Through innovative structural design and material application, it successfully overcomes the balance problem of noise, weight and efficiency in traditional hydraulic motors. Its value lies not only in providing powerful and reliable rotational power, but also in bringing better energy efficiency, more comfortable operating environment, more flexible space layout and longer service life to the entire machine equipment. For modern industrial applications that pursue high performance, high reliability and environmental protection, it is an ideal power solution for enhancing the core competitiveness of products.
o withstand radial forces, with reversible rotation.
