The hydraulic motor, as one of the executive components of the hydraulic system, is a hydraulic device that drives the rotation of equipment components. So how to select the hydraulic motor, what are the precautions in the installation and use process?
How to select a hydraulic motor
The four technical indicators commonly used in hydraulic motors are as follows:
1. Flow rate
① Hydraulic oil is injected into the hydraulic motor, and the injected hydraulic oil is measured by "flow", that is, the volume of hydraulic oil injected into the motor in one minute, and the unit is "L/min".
(2) The hydraulic oil injected into the motor but also outflow, otherwise the hydraulic oil all gathered in the motor, is to cause an explosion, in theory, the flow of hydraulic oil injected into the motor and the flow from the hydraulic motor is equal.
(3) The flow rate and the speed of the motor output shaft are related, they are proportional to the relationship, then we get another invisible parameter of the motor called displacement, that is, the volume of hydraulic oil injected or discharged when the motor rotates, the unit is "ml/r".
The size of the hydraulic motor is measured by displacement, so the size of the motor refers to the displacement.
The flow of the hydraulic motor can be measured by the flow meter, and almost every hydraulic system will arrange a flow meter to monitor the flow of the hydraulic system at any time.
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2. Stress
① Hydraulic oil injection, to drive the motor rotation, so the hydraulic oil needs to have a certain pressure, that is, need a force to drive the hydraulic motor rotation, the driving force is the pressure, and their unit is not "N", but "MPa", which is a unit of pressure, but in the hydraulic pressure is usually called pressure.
The size of the hydraulic motor pressure is determined by the load, not generated by the motor.
(3) The rated pressure of the motor refers to the allowable pressure value when the motor is running continuously.
④ The pressure is measured by the pressure gauge, the range of the pressure gauge is selected according to the maximum pressure of the hydraulic system, and it is best to reserve several pressure gauge interfaces in the design of the hydraulic system in order to monitor the pressure change of the system at any time.
3. Speed
The speed of the hydraulic motor is a parameter that measures the rotation speed of the motor output shaft, which is generally determined by the customer according to the operating speed of the equipment.
The classification of hydraulic motors is defined according to the speed, which is divided into high-speed motors and low-speed motors, high-speed motors are generally more than 500 RPM, and low-speed motors are below 500 RPM.
(3) Hydraulic motors generally have a minimum stable speed, below this value, the motor will appear crawling phenomenon.
4. Torque
① The output shaft of the motor is to drive the mechanical parts to rotate, so the motor must have a certain driving force to drive the mechanical parts, then what are the parameters to measure the driving force of the motor? "Torque", unit "Nm", is the force acting on a moment arm of a certain length.
The amount of torque of the motor is determined by the load, how much torque is needed to drive the load, and the motor will provide how much torque, if the load requires too much torque, the motor will appear with an immobile load, then the motor is overloaded.
③ The measurement of torque is determined with a torque meter.
Precautions in the installation of hydraulic motor
The hydraulic motor, as one of the executive components of the hydraulic system, is particularly important in practical use. But what should you pay attention to during the installation process? When the transmission shaft of the hydraulic motor is connected to other machinery, it should be ensured that it is concentric or flexible. For details, refer to the following steps:
1. The ability of the bearing of the hydraulic motor to bear the radial force, for the motor that can not bear the radial force, shall not be the pulley and other transmission parts directly installed on the spindle.
The active sprocket is driven by a hydraulic motor, and the passive sprocket drives the conveyor belt roller. According to the user's report, the motor often appears oil leakage phenomenon, and the sealing ring replacement in less than 3 months began to leak. What causes the oil leak? The hydraulic motor drives the belt pulley through the chain drive because the chain drive will also produce radial force, and the oil seal deforms after bearing the radial force, resulting in oil leakage.
2. Hydraulic motor chain drive
① The motor leakage pipe should be smooth, and generally do not connect the back pressure, when the leakage pipe is too long or due to some need to connect the back pressure, its size should not exceed the value allowed by the low-pressure seal.
② The external leakage oil should be able to ensure that the motor shell is full of oil, to prevent all the oil in the shell from flowing back to the tank when the shutdown.
(3) For the motor with a long downtime, it can not be operated directly with a full load, and it should be used normally after empty operation for some time.
3. The frame on which the motor is installed should have sufficient stiffness
(1) The support and frame of the motor must have sufficient stiffness to withstand the reaction force exerted on it when the motor outputs torque.
The insufficient rigidity of the frame to install the motor will cause vibration or deformation, and even accidents, and it is impossible to ensure that the concentricity of the connection between the drive machine and the motor shaft is controlled within 0.1mm.
4. Hydraulic motor and gearbox should not be used together
One of the characteristics of hydraulic transmission is that the power-to-weight ratio is large, and under normal circumstances, the hydraulic motor circuit itself can complete the usual speed regulation and transmission functions.
If the hydraulic motor is used together with the gear gearbox, the characteristics of hydraulic control are lost, and the volume and cost of the equipment are significantly increased.
5. The drain port of the hydraulic motor should be returned to the tank separately
Although the oil return pressure is not high from the general concept, the oil return in many hydraulic systems still has a certain pressure, and the oil drain chamber of the hydraulic motor is not allowed to have pressure.
② The interior of the hydraulic motor's oil drain port is connected to the housing cavity, and the shaft seal of the motor shaft only plays a sealing role and is not pressure-resistant. If this port is connected with other return oil lines, it is easy to cause damage to the motor shaft seal, resulting in oil leakage, so it is not allowed to connect the hydraulic motor drain port with other return oil lines.
6. The hydraulic motor should not enter the air
When the hydraulic system is initially working, it will inevitably contain air in the pipeline of the system.
An important part of system debugging is to exhaust the air in the system, which is especially important for hydraulic motors.
The hydraulic medium in the motor has a process of sudden change from high pressure to low pressure, and the process frequency is very high, on average about 10 times per revolution.
When the hydraulic oil in the motor contains air, it will locally produce cavitation at the pressure mutation, so that the motor is soon damaged.
