When you are designing hydraulic systems or making a purchase for equipment, do you consider how to achieve stable and high torque output within a compact structure? The gerotor hydraulic motor may be a good choice. This article will provide you with a detailed introduction.
What is a Gerotor Hydraulic Motor?
The gerotor hydraulic motor is a hydraulic actuator that adopts an internal meshing structure. It can convert hydraulic energy into rotational mechanical energy. The gerotor hydraulic motor is a low-speed high-torque hydraulic motor.
Advantages of Gerotor Hydraulic Motor
Low-Speed High-Torque Output
The most obvious advantage of a gerotor hydraulic motor is its ability to output strong power at low speeds. You don’t need to install additional transmission devices such as gearboxes. This can simplify the overall structure of your device and reduce energy loss caused by the longer transmission path.
High Power Density
The power density refers to the power that a motor can output per unit volume. The gerotor hydraulic motors have a very high power density among various motors of the same size. It can provide the highest output power with the smallest size. You can install it in devices with limited space but demanding high power output.
Compact Structure
Compared to other types of hydraulic motors of the same torque level, the gerotor hydraulic motor has a smaller volume and lighter weight. On mobile equipment such as agricultural machinery, loaders, and cleaning vehicles, the gerotor hydraulic motor can be directly embedded in attachment drive positions or compact wheel hubs.
This can help your device achieve lightweight and miniaturization, reducing the complexity of device layout.
Good Startup Performance
It is very important for the device to start smoothly under load when in use. The gerotor hydraulic motors can provide a large starting torque during startup.
Whether starting agricultural machinery in mud or conveyor belts under heavy loads, the gerotor hydraulic motor can keep a smooth equipment start-up and reduce system impact caused by insufficient starting power.
Easy Installation and Maintenance
The installation of the gerotor hydraulic motor is very convenient. All you need to do is connect the oil pipe to the inlet and outlet ports of the motor, and then it can start working. By changing the direction of the oil flow, you can easily control the forward and reverse rotation of the motor.
Meanwhile, the moving parts of the gerotor hydraulic motor are fewer. This simple structure reduces the probability of equipment failure, helping you lower the maintenance difficulty and costs.
Smooth Operation and Low Noise
During the movement, the teeth of the rotor and stator make continuous and gentle contact with each other, resulting in a relatively small flow pulsation. The vibration amplitude and noise level of the gerotor hydraulic motor during operation are at a relatively low level.
The low noise and smooth operation of the gerotor hydraulic motor make it very suitable for you that require quiet working environments or precise control of operating speed.
Working Principle of the Gerotor Hydraulic Motor
The gerotor hydraulic motor is mainly composed of an inner rotor, an outer stator, a distribution mechanism, and bearings. The inner rotor and outer stator are the key structures of the gerotor hydraulic motor.
The inner rotor has an external tooth structure and usually has N teeth. It is typically connected to the output shaft. The outer stator has an internal tooth structure with N + 1 teeth. The inner rotor is eccentrically installed inside the stator, and a series of sealed volume cavities are formed between them.
When high-pressure hydraulic oil enters the volume chamber through the distribution mechanism, a high-pressure zone is formed on one side of the chamber and a low-pressure zone is formed on the other side.
Under the influence of pressure difference, the rotor will simultaneously undergo two types of movements: low-speed rotation around its own axis, and high-speed reverse revolution around the center of the stator. This type of composite motion is called orbital motion.
During this process, the volume chamber between the rotor and stator will continuously undergo volume changes. The chamber volume on the intake side keeps expanding to draw in the high-pressure oil. Meanwhile, the volume of the chamber on the discharge side gradually decreases, discharging the oil.
The orbital motion of the inner rotor is transmitted to the output shaft, thereby converting hydraulic energy into continuous rotating mechanical energy.
Application of the Gerotor Hydraulic Motor
Agricultural Machinery
Agricultural machinery is one of the most widely used fields for gerotor hydraulic motors. Most of the seeders, sprayers, harvesters, and fertilization equipment need to complete their operations at low speeds.
In the complex working environment of the field, the gerotor hydraulic motor can maintain low-speed and stable output, improving the agricultural machinery operation efficiency.
Engineering Machinery
The gerotor hydraulic motor is commonly used in excavators and crawler loaders. This equipment typically operates in complex terrain and high load conditions. The gerotor hydraulic motor can provide a stable output.
At the same time, the compact structure of the gerotor hydraulic motor can reduce the volume and weight of your equipment and enhance the flexibility of equipment layout.
Material Handling
In industrial automation and material conveying systems, the gerotor hydraulic motors are mainly used for driving conveyor belts, screw conveyors, hoisting systems, etc. The gerotor hydraulic motor can provide stable output and speed regulation, adapting to long-term operation conditions.
It can be directly integrated into the drive equipment inside the drum or winch. This reduces the use of gearboxes and reducers, minimizes energy loss, and improves the operational efficiency of your equipment.
Sanitation Vehicles
Sanitation vehicles such as sweepers and garbage compactors have requirements for noise and stability. The low noise and stable output characteristics of the gerotor hydraulic motor can well meet these requirements.
Factors to Consider When Choosing a Gerotor Hydraulic Motor
Torque and Load Matching
When choosing a gerotor hydraulic motor, you need to understand the continuous torque during normal operation and the peak torque during startup of the equipment. If your equipment has frequent load starting conditions, you should pay more attention to the starting efficiency of the motor.
You can reserve a safety margin of about 20% based on the actual load torque. This can make sure that your equipment has a stable power output when facing sudden impacts and load conditions.
Work Pressure
The pressure determines the torque output of the gerotor hydraulic motor. You need to confirm the continuous working pressure, intermittent pressure, and peak pressure of the system. In order to extend the service life of your gerotor hydraulic motor, we recommend operating the motor within the rated continuous pressure range.
Displacement and Rotational Speed
The displacement represents the volume of hydraulic oil required by the motor for each revolution. It determines the speed range under a given flow condition. You can calculate whether the motor speed is within the equipment’s required range by reversing the calculation based on the flow provided by the hydraulic power unit.
If your equipment requires extremely low rotational speed conditions, you should also make sure the smooth operation of the gerotor hydraulic motor at extremely low speeds.
Interface Compatibility
When choosing a gerotor hydraulic motor, please confirm the installation flange specifications, output shaft type, and oil port thread standards of the motor.
Make sure that these parameters are compatible with the transmission components and pipelines of your equipment. This can reduce the use of adapter parts, improve the transmission accuracy, and make the equipment operate more smoothly.
If the back pressure of your system’s return oil pipeline is high or the motor adopts a series layout, you need to choose a gerotor hydraulic motor with an external drain port. This way, the internal pressure of the shell can be directly returned to the oil tank, preventing the bearings from being damaged due to excessive back pressure.
Lateral Load Bearing Capacity
If you need to directly connect the output shaft of a gerotor hydraulic motor to a sprocket, gear, or pulley, the shaft end will bear radial and axial loads. You should carefully refer to the axial and radial load curve charts provided by the manufacturer.
Meanwhile, if your equipment is operating under heavy-load conditions, you need to select a gerotor hydraulic motor with a heavy-load bearing configuration. If necessary, you should also add bearing brackets.
Work Environment
You need to select the appropriate sealing material and protection level of the gerotor hydraulic motor based on the working environment conditions, such as temperature, humidity, dust and corrosion.
At the same time, make sure that the motor is compatible with the hydraulic oil you are using. The gerotor hydraulic motors have high requirements for oil cleanliness. You need to control the filtration accuracy of the system to reduce the wear of the rotor and stator caused by impurities.
Gerotor Hydraulic Motor vs Geroler Hydraulic Motor
Structure
The structure of the gerotor hydraulic motor is simpler. The structure of the geroler hydraulic motor is relatively complex.
The gerotor hydraulic motor adopts a structure where the inner rotor and outer stator directly mesh. The number of teeth on the inner rotor is usually one less than that on the outer stator, and they have a small axial eccentricity. The rotor tooth surface directly slides and contacts the stator tooth surface, forming a sealed volume chamber.
The geroler hydraulic motor is an improvement based on the gerotor hydraulic motor structure. Its stator teeth are embedded with cylindrical rollers. The rotor teeth surface does not directly contact the stator, but forms rolling contact with these rollers.
Friction and Wear
When the gerotor hydraulic motor is in operation, there is sliding friction between the rotor and the stator. Sliding friction generates relatively high frictional resistance. Under high pressure and low speed conditions, the friction loss becomes more pronounced.
After long-term use, the contact surfaces are prone to wear, which may result in decreased sealing performance and increased leakage.
The geroler hydraulic motor achieves rolling friction through rollers, thereby reducing the friction coefficient. This can reduce energy loss, minimize component wear, and improve the durability of the motor under high pressure and continuous working conditions.
Low-Speed Operation Performance
The gerotor hydraulic motor can operate smoothly under low-speed conditions. The sliding friction of the tooth surface limits the minimum stable speed it can achieve under load conditions. At extremely low rotational speeds, due to sliding friction, the gerotor hydraulic motor may experience stick-slip, resulting in fluctuations in the output speed.
The rollers in geroler hydraulic motors can compensate for manufacturing tolerances and reduce friction pulsation, thereby reducing stick-slip or vibration at extremely low speeds. For equipment that requires extremely low speed and smooth operation, the geroler hydraulic motor is a better choice.
Operating Efficiency
The gerotor hydraulic motor has a simple structure. However, due to the sliding friction, its mechanical efficiency may decrease under high-load working conditions.
The geroler hydraulic motor reduces friction losses through rolling contact and usually has higher mechanical efficiency and volumetric efficiency.
Pressure Resistance
The gerotor hydraulic motor has a hard-on-hard sliding contact. Under high pressure, the wear rate of the tooth surfaces is relatively fast. Therefore, you can use it for applications with medium to low voltage and intermittent operation.
The geroler hydraulic motor can withstand higher working pressure. The roller structure can evenly distribute the load.
FAQs
Why does the Gerotor Hydraulic Motor Require High Cleanliness of Hydraulic Oil?
The rotor and stator inside the gerotor hydraulic motor are precisely matched. And the gap between them is usually only at the micron level. If there are solid particles in the hydraulic oil, these impurities will wear down the teeth of the rotor and stator under high pressure.
When the gap increases due to wear, the volumetric efficiency of the motor will decrease and the output torque will be insufficient. We recommend that your system be equipped with a filter with a filtration accuracy of no less than 20 micrometers to keep the normal service life of the motor.
Can the Gerotor Hydraulic Motor be Installed Vertically?
Yes. When installing vertically, especially when the shaft end is upward, there are certain points you need to pay attention to. The bearings and seals at the top of the motor may not receive sufficient lubrication through internal circulation of oil and are prone to accumulating air.
To make sure that your motor operates reliably in the long term, you need to perform the exhaust process before the initial startup. And confirm that the internal pressure of the system is sufficient to allow the hydraulic oil to reach and lubricate the top moving parts.
Can the Gerotor Hydraulic Motor Operate in both Directions?
Yes. Most gerotor hydraulic motors support bidirectional operation. By changing the direction of the inlet and outlet ports, the motor can achieve forward and reverse rotation. This is particularly important for devices that require reciprocating motion or direction changes.
However, you need to confirm the flow distribution structure inside the motor and the oil discharge ports. Otherwise, during the reverse operation, there may be problems such as excessive sealing pressure or insufficient internal lubrication.
In working conditions involving frequent reversing, it is recommended that you choose a model that clearly supports bidirectional operation.
Why does the Gerotor Hydraulic Motor Overheat?
The overheating of gerotor hydraulic motors is usually caused by excessive load, contaminated hydraulic oil or insufficient cooling. When the gerotor hydraulic motor operates under high pressure or high load conditions for a long time, the internal friction increases and the heat generated increases.
Hydraulic oil contamination or insufficient oil volume will reduce the lubrication and heat dissipation capabilities, leading to an increase in temperature. If your system has poor heat dissipation or the environmental temperature is too high, it will also cause the motor to overheat.
What are the Common Reasons for Abnormal Noise in the Gerotor Hydraulic Motor?
Insufficient hydraulic oil, mismatched viscosity, or excessive impurities can lead to poor lubrication, causing dry friction noise between the rotor and the stator. Excessive coaxiality deviation between the motor and the load, as well as insufficient rigidity of the installation bracket, can also lead to increased vibration during operation and result in abnormal noises.
Final Thoughts
An appropriate gerotor hydraulic motor can provide you with stable high torque output at low speeds. At the same time, its compact structure enhances the flexibility of your equipment layout. Welcome to contact us to choose high-quality gerotor hydraulic motors to enhance your equipment production efficiency.
