A Hydraulic Motor Provides Power and Control
The hydraulic motor is the central component in a hydraulic circuit. Converting hydraulic pressure into kinetic energy is the most important task in a hydraulic system. The motor is therefore one of the “actuators,” meaning the components that perform an “action.”
The Hydraulic Motor Has One Task but Offers Two Solutions
A hydraulic motor converts hydraulic pressure into motion. At this point, a distinction is made between linear and radial movements, with different solutions offered accordingly.
Linear Movement with a Hydraulic Motor
Linear movement encompasses all movements that follow a straight path. The actuator is accordingly called a “hydraulic linear motor.” These are the familiar hydraulic cylinders in which a piston is extended from a sleeve by hydraulic pressure. Linear motors can primarily be distinguished by two designs:
Single-acting hydraulic cylinders can only extend but cannot retract independently. They are used wherever an external force is available to return the linear motor to its initial position. Typical examples include hydraulic cranes, car jacks, or transmission jacks. Here, gravity takes over the task of pushing the cylinder back together after hydraulic relief.
Double-acting cylinders have a second hydraulic inlet. The hydraulic medium can be redirected through this inlet. This pushes the piston of the linear motor back to its end position. Double-acting hydraulic cylinders are therefore used wherever no external force is available for the return stroke.
Powerful Rotary Movement with Radial Motors
As simple as a hydraulic linear motor is in design, it becomes complex when a rotary movement, especially continuous rotation, is to be achieved with hydraulic pressure. With radial motors, there is the additional factor that, as always in hydraulics, they are primarily intended to apply large forces (in the case of radial movements, these are torques) rather than to achieve high speeds. This makes the construction of hydraulic radial motors more difficult.
The reverse task is the provision of hydraulic pressure through an external radial movement. Here, the industry offers a variety of solutions. Producing a technically usable radial movement through hydraulic pressure, however, is more difficult. Where simple gear motors cannot provide the desired torque, technically complex axial or radial piston motors are used. Where only a circular arc is to be executed hydraulically, compromises are often chosen. Linear motors are used for this purpose, which can perform the desired partial radial movement during extension through a clever lever and deflection system. However, if the circular movement is to be continuous, the solutions described remain the options. These are found, for example, in particularly heavy vehicles such as tanks, mobile cranes, handling machines, tracked vehicles, and other work equipment.