Hydraulic Motors

About Hydraulic Motors and Hydraulic Motor Manufacturers Including: Hydraulic Power Units, Hydraulic Pump Motor, Hydraulic Systems, Hydraulic Wheel Motors & Small Hydraulic Motors.

Hydraulic motors are a common component in a larger hydraulic system. Hydraulic motors convert hydraulic energy into mechanical energy. In industrial hydraulic systems, pumps and motors are typically used in conjunction with proper valves and piping to form a hydraulic powered transmission. Usually, a pump is connected via a carrier line to a motor, which then draws fluid from a reservoir and forces it into the motor. The fluid forces the movable components of the motor into motion, which in turn rotates the attached shaft. The shaft, which is mechanically linked to the work load, provides rotary mechanical motion. Finally, the fluid is discharged at low pressure and transferred back to the pump.

Most hydraulic motor manufacturers produce fixed-displacement hydraulic motors. Displacement is a motor rating refering to the amount of flow that is required for a specified drive speed. Variable-displacement piston motors are also utilized, but mostly in hydrostatic drives. Other important ratings of a motor are torque and pressure. These ratings indicate how much load a hydraulic motor is capable of handling. Hydraulic motors are entirely enclosed and self-contained. These characteristics allow them to be submerged or operated in many hostile environments.

Three types of hydraulic motors are gear, vane and piston-type motors. Each of these types can be produced by hydraulic motor manufacturers as either unidirectional or reversible, although most motors used in mobile equipment are the latter. In hydraulic gear motors, one of the two driven gears is attached to the output shaft. Gear motors, which are the least expensive but the noisiest of the hydraulic motors, have the ability to operate at high speeds; however, they are inefficient at low speeds. In a hydraulically balanced vane motor, the vane on the inlet port side of the motor is subject to full system pressure, while the chamber leading the vane is subject to the much lower outlet pressure, forcing oil through the motor and, as a result, developing torque. Hydraulic vane motors are the most popular general-purpose motor, but they are limited by their tolerance to high pressure systems and the higher percentage of slippage or internal leakage relative to the lower total fluid flow at low speeds. Hydraulic piston pumps can be either axial or radial and are generally the most expensive of the hydraulic motors. They have advantages over the other motors, however, in that piston motors are far more adaptable to high torque, low speed operation and higher system pressure applications.

Hydraulic motor manufacturers provide hydraulic motors that are solutions in applications involving infinite speed control, stalling under full torque, high power-to-weight ratio and small size. Their characteristics make them useful in a wide variety of industries. The aerospace industry uses hydraulic motors to actuate wing flaps. The food processing industry uses them to power automated manufacturing machinery. Hydraulic motors are also used in trenchers, construction equipment, waste management and recycling, forestry, agriculture, dredging and industrial processing. Other applications for hydraulic motors include drives for marine winches, submersible ROV’s, conveyor and auger systems and mining equipment.

Types of Hydraulic Motors

• Axial piston hydraulic motors use pistons along one axis, as opposed to the radial piston motors, which are circular. Axial piston hydraulic motors are designed to withstand higher torque.
  
• Hydraulic drum motors are an advanced and highly efficient conveyor drive system in which the motor, transmission and bearings are totally enclosed within the drum shell.
  
• Hydraulic gear motors consist of an inner and an outer gear. The pressure pushes the gears around a center point, turning a shaft.
  
• Hydraulic power units provide pressurized flow to hydraulic-powered mechanisms.
  
• Hydraulic pump motors are single, variable-speed hydraulic motors that are used for steering and lifting applications.
  
• Hydraulic systems convert hydraulic energy into mechanical power.
  
• Hydraulic wheel motors have very few parts. Hydraulic wheel motors can run forward or backward, depending on the direction in which the hydraulic fluid is injected.
  
• Hydraulic vane motors, the most popular general purpose hydraulic motor, consist of spring loaded vanes that are connected to a rotor. The vanes slide in and out of the slots in the rotor to make contact with the vane wall.
  
• Radial piston hydraulic motors act much like a cylinder. Radial piston hydraulic motors are high power and highly efficient.
  
• Roller hydraulic motors, a type of orbital hydraulic motor, have rollers that are hydro-dynamically supported to minimize friction, ensuring maximum durability and high output at high pressure.
  
• Rotor hydraulic motors, a type of orbital hydraulic motor, are particularly suited for long working cycles at average pressure. Rotor motors are operated by lobes that are fixed and set directly on the stator.
  
• Small hydraulic motors have relatively small stroke lengths.

Hydraulic Motor Terms

Aeration – Air in hydraulic fluid.

Accumulator – A container that stores fluid under pressure. Accumulators, the common types of which are piston, bladder and diaphragm, are used as an energy source or to absorb hydraulic shock.

Cylinder – A device that converts hydraulic energy into linear mechanical motion and force.

Displacement – The amount of fluid that passes through a pump, motor or cylinder in a period of time or during a single actuation event, such as a revolution or stroke.

Dry Friction Coefficient – The degree of friction that results from the contact between the moving surfaces of a motor shaft.

Filter – A device within a hydraulic system that is used to remove contaminants from the oil.

Fluid Power System – A system that utilizes fluid pressure to transmit and control power.

Gear – A toothed wheel used to transfer mechanical energy.

Hydraulics – The science dealing with the transmission of force through the medium of a contained fluid.

Hydraulic Tester – A device that is used to troubleshoot and check hydraulic-powered system components.

Line – A tube, pipe or hose that acts as a conductor of hydraulic fluid.

Oil – A slippery and viscous liquid that is not miscible with water. Oil is often used in hydraulic systems because it cannot be compressed.

Piston – A cylindrical piece of metal that moves up and down inside the cylinder of a hydraulic motor.

Pressure Plate – A plate on the side of a gear or vane pump or motor cartridge that is used to keep clearance and slippage to a minimum.

Pump – A mechanical device that transports liquids and gases by suction or pressure.

Resistance – In hydraulics, the condition engendered by an obstruction or restriction in the flow path.

Shaft – A device that is mechanically attached to the work load and provides rotary motion in motors.

Stroke – The movement of an element of a valve spool, cylinder rod or pump or motor displacement in a straight line that sets the limits of motion.

Throttle – A restriction to the normal flow of fluid.

Torque – The measure of the force applied to produce rotational motion, usually measured in foot-pounds.

Valve – A device that controls fluid flow rate, direction or pressure.

Vane – In a hydraulic motor, a flat surface that rotates and pushes against the fluid.