HYDRAULIC MOTORS

What is hydraulic motors?

Hydraulic motors are rotary actuators that convert hydraulic, or fluid energy into mechanical power. They work in tandem with a hydraulic pump, which converts mechanical power into fluid, or hydraulic power. Hydraulic motors provide the force and supply the motion to move an external load.

The design of a hydraulic motor and a hydraulic pump are very similar. For this reason, some hydraulic pumps with fixed displacement volumes may also be used as hydraulic motors. A hydraulic motor works the other way round as it converts hydraulic energy into mechanical energy: a rotating shaft. It uses hydraulic pressure and flow to generate the required torque and rotation. The power produced by a hydraulic motor is determined by the flow and pressure drop of the motor.

The design of hydraulic pumps and motors is very similar, some pumps can be use as hydraulic motor.

You can use hydraulic motors for many applications, such as winches, crane drives, self-driven cranes, excavators, mixer and agitator drives, roll mills, etc. The hydraulic motor must be geared to hydraulic system requirements; issues such as load, range of load, speed, serviceability, etc. must be taken into account. There are different types of hydraulic motors, such as hydraulic gear motors, piston motors and hydraulic vane motors.

Hydraulic drive systems use pressurized hydraulic fluid to power hydraulic machinery. These systems are comprised of hydraulic pumps, motors and cylinders.

Hydraulic motors convert hydraulic pressure and flow into torque and rotation, providing the force and motion to move an external load.

A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement. The hydraulic motor is the rotary counterpart of the hydraulic cylinder. Conceptually, a hydraulic motor should be interchangeable with a hydraulic pump because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator. However, most hydraulic pumps cannot be used as hydraulic motors because they cannot be backdriven.

Also, a hydraulic motor is usually designed for the working pressure at both sides of the motor. Hydraulic pumps, motors, and cylinders can be combined into hydraulic drive systems. One or more hydraulic pumps, coupled to one or more hydraulic motors, constitutes a hydraulic transmission. One of the first rotary hydraulic motors to be developed was that constructed by Armstrong for his Swing Bridge over the River Tyne. Two motors were provided, for reliability. Each one was a three-cylinder single-acting oscillating engine. Armstrong developed a wide range of hydraulic motors, linear and rotary, that were used for a wide range of industrial and civil engineering tasks, particularly for docks and moving bridges.

Where are hydraulic motors used?

Hydraulic motors are used in any application requiring rotational force, also known as torque. A hydraulic motor converts hydrostatic energy into mechanical energy by pushing vanes, gears or pistons attached to a crankshaft. The power capacity of a hydraulic motor is dictated by its displacement, and the speed in which is rotates.

Hydraulic motors are used in industrial applications such as augers, conveyors, and mixers, as well as rolling mills, where their robust nature and resistance to heat make them a perfect solution. Hydraulic motors can be used in any application an electric motor can, but require no electricity, and can withstand more environmental extremes, such as submersion and extreme heat. Motors can be sized small enough for high-speed drills, or large enough for injection molding machines.

Hydraulic motors are especially well suited to mobile machinery, where they are the primary drive for most off-highway equipment. Hydrostatic drive systems act to transmit engine power to the drive wheels, with exceptional versatility and reliability. Hydraulic wheel motors are used on wheeled loaders, skid-steer loaders, articulating loaders and backhoe loaders, where the motor’s quick and smooth reversibility make them perfect for the application.

Motors are also used in tracked vehicles, such as excavators of all sizes, bulldozers, and specialty machines, such as bridge-layers or drill rigs. The high power density of hydraulic motors allow them to achieve earth-moving torque in a relatively small package. Hydraulic motors can also be used in hybrid hydraulic vehicle drive systems, where the motor can also absorb energy from the drive wheels to pump fluid into an accumulator, which can subsequently send flow back to that motor for a burst of acceleration from low speed.

View more: Hydraulic power units, hydraulic cyliners

Hydraulic motor types

There are four types of hydraulic motors, generally classified as high speed, low torque (HSLT) or low speed, high torque (LSHT):

Gear Motors

Hydraulic gear motors are often used in mobile hydraulics and in agricultural machinery. As well as applications that require high output speed of the hydraulic motor.

Gear motors feature two gears, one being the driven gear—which is attached to the output shaft—and the idler gear. Their function is simple: High-pressure oil is ported into one side of the gears, where it flows around the gears and housing, to the outlet port and compressed out of the motor. Meshing of the gears is a bi-product of high-pressure inlet flow acting on the gear teeth. What actually prevents fluid from leaking from the low pressure (outlet) side to high pressure (inlet) side is the pressure differential. With gear motors, you must be concerned with leakage from the inlet to outlet, which reduces motor efficiency and creates heat as well.

A gear motor (external gear) consists of two gears, the driven gear (attached to the output shaft by way of a key, etc.) and the idler gear. High pressure oil is ported into one side of the gears, where it flows around the periphery of the gears, between the gear tips and the wall housings in which it resides, to the outlet port. The gears then mesh, not allowing the oil from the outlet side to flow back to the inlet side. For lubrication, the gear motor uses a small amount of oil from the pressurized side of the gears, bleeds this through the (typically) hydrodynamic bearings, and vents the same oil either to the low pressure side of the gears, or through a dedicated drain port on the motor housing, which is usually connected to a line that vents the motor's case pressure to the system's reservoir. An especially positive attribute of the gear motor is that catastrophic breakdown is less common than in most other types of hydraulic motors. This is because the gears gradually wear down the housing and/or main bushings, reducing the volumetric efficiency of the motor gradually until it is all but useless. This often happens long before wear causes the unit to seize or break down.

Piston Motors

Piston motors are hydraulic motors with a high speed and displacement range that operate under high efficiency at maximum pressure of up to 450 bar.

Piston-type motors are available in a variety of different styles, including radial-, axial-, and other less common designs. Radial-piston motors feature pistons arranged perpendicularly to the crankshaft’s axis. As the crankshaft rotates, the pistons are moved linearly by the fluid pressure. Axial-piston designs feature a number of pistons arranged in a circular pattern inside a housing (cylinder block, rotor, or barrel). This housing rotates about its axis by a shaft that is aligned with the pumping pistons. Two designs of axial piston motors exist—swashplate and bent axis types. Swashplate designs feature the pistons and drive shaft in a parallel arrangement. In the bent axis version, the pistons are arranged at an angle to the main drive shaft.

Vane Motors

Vane motors are used in hydraulic applications for industrial and mobile equipment. We supply Denison Hydraulics vane motors and spare parts from stock. A rectangular vane moves in and out of the center rotor, which is connected with an output shaft. This output shaft rotates when hydraulic fluid is applied to the vane.

At the medium-pressure and cost range, vane motors feature a housing with an eccentric bore. Vanes rotor slide in and out, run by the eccentric bore. The movement of the pressurized fluid causes an unbalanced force, which in turn forces the rotor to turn in one direction.

A vane motor consists of a housing with an eccentric bore, in which runs a rotor with vanes in it that slide in and out. The force differential created by the unbalanced force of the pressurized fluid on the vanes causes the rotor to spin in one direction. A critical element in vane motor design is how the vane tips are machined at the contact point between vane tip and motor housing. Several types of "lip" designs are used, and the main objective is to provide a tight seal between the inside of the motor housing and the vane, and at the same time to minimize wear and metal-to-metal contact.

What is difference between hydraulic pump and hydraulic motor?

There is no difference as far as design and construction of the liquid head is concerned. However hydraulic pump can be differentiated from hydraulic motors very easily since pump will be coupled to an electric motor. Further the two have very different functions within the circuit, while hydraulic pumps add energy to the system by pushing the hydraulic fluid; motors on other hand act as a rotary actuator and develop torque and rotating motion.

Hydraulic motors are rotary actuators. However, the name rotary actuator is reserved for a particular type of unit that is limited in rotation to less than 360.A hydraulic motor is a device which converts fluid power into rotary power or converts fluid pressure into torque. Torque is a function of pressure or, in other words, the motor input pressure level is determined by the resisting torque at the output shaft. A hydraulic pump is a device which converts mechanical force and motion into fluid power. A hydraulic motor is not a hydraulic pump when run backward. A design that is completely acceptable as a motor may operate very poorly as a pump in a certain applications. Differences between a hydraulic motor and a hydraulic pump are given below.

Hydraulic Motor : It is a device for delivering torque at a given pressure. The main emphasis is on mechanical efficiency and torque that can be transmitted. Motors usually operate over a wide range of speed, from a low RPM to high RPM. Most motors are designed for bidirectional applications such as braking loads, rotary tables. Motors may be idle for long time. Motors are subjected to high side loads (from gears, chains, belt-driven pulleys).

Hydraulic Pump:It is a device for delivering flow at a given pressure. The main emphasis is on volumetric efficiency and flow. Pumps usually operate at high RPM. In most situations, pumps usually operate in one direction. Pumps usually operate continuously. Majority of pumps are not subjected to side loads. Usually pumps are pad mounted on power pack top and shaft is connected to the prime mover directly.

Hydraulic pumps, motors, and cylinders can be combined into hydraulic drive systems. One or more hydraulic pumps, coupled to one or more hydraulic motors, constitute a hydraulic transmission.

Hydraulic motors are used for many applications now such as winches and crane drives, wheel motors for military vehicles, self-driven cranes, excavators, conveyor and feeder drives, cooling fan drives, mixer and agitator drives, roll mills, drum drives for digesters, trommels and kilns, shredders, drilling rigs, trench cutters, high-powered lawn trimmers, and plastic injection machines. Hydraulic motors are also used in heat transfer applications.

Dinh Linh specializes in consulting and supplying all kinds of piston, gear, vane, hydraulic motor brands of Yuken, Parker and Danfoss in Ho Chi Minh, Hanoi, Binh Duong and all over the country. Customers looking to buy hydraulic motor in the price please contact us for detailed advice