When it comes to the cycloid hydraulic motor, the first thing that comes to mind is its housing and powerful torque. But when you take a closer look, you will find that it is not like a normal hydraulic motor that only has two oil pipes, but has three! Why does the cycloid hydraulic motor have three oil pipes?

Generally speaking, there are two main oil pipes in a hydraulic motor: the oil inlet pipe and the oil return pipe. The oil inlet pipe is responsible for sending high-pressure oil into the motor to make it move; the oil return pipe returns the used low-pressure oil to the oil tank to form a closed loop. This is the most basic hydraulic motor pipeline configuration.

What is the third hydraulic oil pipe of the cycloidal hydraulic motor for? It is actually an oil drain pipe, which plays a vital role in the cycloidal hydraulic motor.

1.Functions of the drain pipe:

(1) Draining internal leaked oil

There are many rotating and sealing parts inside the cycloidal hydraulic motor. No matter how sophisticated the design is, there will always be a small amount of hydraulic oil leaking from the high-pressure chamber into the shell. If this part of the oil is not discharged in time, the pressure inside the shell will become higher and higher, eventually causing damage to the oil seal or even bursting. This is the first function of the drain pipe – to safely drain the excess oil back to the oil tank.

(2) Protect the oil seal and extend the life of the motor

If there is no drain pipe, the internal pressure is too high, which can easily break the oil seal, causing oil leakage and even affecting the normal operation of the motor. The drain pipe can keep the internal pressure stable, reduce the working pressure of the oil seal, and extend its life.

(3) Avoid the influence of back pressure

If the drain pipe is directly connected to the return pipe, it may cause the shell pressure to increase and affect the operation of the motor. Therefore, the drain pipe is usually connected back to the oil tank separately, which can ensure that the motor is always in a stable low-pressure state.

2. What will happen if there is no drain pipe?

(1) The oil seal is easily damaged, causing the motor to leak oil

(2) The internal pressure is too high, affecting the life of the motor

(3) High back pressure affects the efficiency of the motor and even causes abnormal shutdown

3. The three oil pipes of the cycloidal hydraulic motor each have their own functions:

(1) Oil inlet pipe:

high-pressure oil enters and drives the motor to rotate

(2) Oil return pipe:

low-pressure oil returns to the oil tank to form a cycle

(3) Drain pipe:

discharges leaked oil in the housing, protects the oil seal, and reduces internal pressure

This is the real reason why the cycloidal hydraulic motor has one more oil pipe than ordinary hydraulic motors. It is not redundant, but to make your hydraulic system more stable and durable!