Hydraulic orbital motors provide high torque at low speed. This makes them the preferred source of rotary motion in many mobile equipment and heavy-duty industrial applications.

In common with other industrial and motive power technologies, hydraulic orbital motors continue to improve. This is making them a practical option in applications that previously could only be satisfied by electric motors. This blog will inform readers about these trends and advances so they can make educated decisions about adopting this motor technology.

Principles and Applications of Hydraulic Orbital Motors

These motors use a gerotor to convert fluid power into motion. A gerotor comprises a small rotor gear inside a larger stator ring. The stator has teeth of the same profile as those on the rotor, so the rotor can roll around the inner surface of the stator.

The rotor has one fewer teeth than the stator, and the teeth are shaped in a manner that ensures two opposite points of the rotor are always in contact with the stator. This divides the space between rotor and stator into two chambers.

In operation, pumping fluid into one chamber makes the rotor turn towards the low pressure side. A valve mechanism rotates the inlet and outlet ports with the rotor. The rotor itself is coupled to an output shaft that provides rotary motion.

Hydraulic orbital motors are used in a range of mobile equipment applications, both as wheel motors and to power ancillary equipment. Skid steers, sweepers and scissor lifts are three examples. They are also used in large industrial equipment like extrusion machines and presses, and to drive conveyors.

Market Needs

Hydraulic orbital motors satisfy the need for low speed, high torque rotary power. However, the businesses that integrate them into their equipment would like to see improvements in the following aspects:

• Form factor and power density: smaller and more powerful will make integration easier
• Weight: Lighter motors allow more payload
• Noise: Although not a major concern, quieter-running motors would be of interest
• Life: Rotor and stator teeth wear over time, necessitating periodic rebuilds
• Efficiency: Improvements may allow use of smaller, lighter motors

Innovations, Advances, and Research

To meet these needs, R&D teams are working on:

• New teeth profiles: The standard gerotor form is described as a “trochoidal-envelope toothed gear set.” Researchers are investigating whether alternative forms would increase torque and efficiency.
• Lightweight designs: Alternative materials, including engineering plastics like polyoxymethylene (POM) are under investigation as substitutes for the hardened steel and stainless steel widely used today.
• Lower friction surfaces: The challenge is to reduce friction between rotor and stator while retaining the seal that stops fluid leaking from high to low pressure regions. Improvements in precision machining of tooth forms are being sought, but in parallel, micro-textured surfaces are also under consideration.
• Wear reduction/life extension: Wear on the tooth forms leads to leaks that reduce output torque. One approach being studied is to apply special wear-resistant coatings that will extend the intervals between motor rebuilds.

Trends in Industrial and Commercial Hydraulics

Motor design and manufacture are not the only aspects of hydraulic power where innovation is taking place. The major broad industry trends are:

• Switching to variable speed drives: Used to control pump speed, these can provide significant energy savings over motors that run at full speed all the time and require hydraulic fluid bypass circuits.
• Equipment health monitoring: Sensors measuring characteristics like temperature and vibration can send data to machine health monitoring systems. This will drive predictive maintenance strategies where maintenance is only carried out when trends indicate a rising chance of failure.
• Transition to biodegradable fluids: Businesses in many sectors are under pressure or already seeking to improve their sustainability ratings. Particularly for mobile equipment going into potentially environmentally sensitive areas, (forestry, for example), the use of biodegradable hydraulic fluid is an important advance.

Better Performance With Hydraulic Power

While hydraulic orbital motors are robust and proven, improvements and upgrades will address the customer desire for longer life and higher performance. As a leader in these high torque, low speed motors, Impro implements improvements that widen the market and increase customer satisfaction.

Whether you’re looking for hydraulic orbital motors for a specific application, or are just exploring the potential of the technology, we’d like to help. Contact us to schedule a discussion.