The lowest stable speed hydraulic motor is an important technology index of the hydraulic motor, its performance and life of the machine has a direct impact. Therefore, in the engineering design and application of the hydraulic system, sometimes chosen minimum steady speed characteristics of hydraulic motor is often need to consider one of the important characteristics.
A, the meaning of the lowest stable speed hydraulic motor
About the meaning of the lowest stable speed of hydraulic motor, the author fully study, research predecessors on the basis of existing research results, combined with engineering project, the lowest stable speed, and the following description of the meaning of:
1. Any by hydraulic motor as power components of hydraulic system, there are determined by the hydraulic system working condition of internal and external conditions of the lowest stable speed nmmin work.
2. The lowest stable speed is under the condition of known parameters of hydraulic system, and can remain stable for a long time to a low speed does not produce "creeping" phenomenon of even the minimum speed limit.
3. The so-called basic steady speed available speed fluctuating rate of the delta n size to signal.
Delta n speed pulse rate can be 10%, also can be more than 10%, its value shall be made to determine the technical requirements for engineering application, but do not allow any zero stop for a short period of time. Velocity phenomenon, namely the "creeping" phenomenon. As the name implies, the minimum stable speed is basically stable, any angular velocity and angular acceleration is zero the stop of the "creeping" phenomenon, namely is unstable, inconsistent with definitions, and the hydraulic motor, hydraulic system itself, and was charged with load object will produce harm.
4. The minimum stable speed nmmin is the study of the hydraulic system of hydraulic motor is the motor at low speed area relative to the rated speed nr. The law of the minimum stable work speed and its limit value. Generally the workspace in the motor at low speed of hydraulic motor under the rated speed nr 5 ~ 15%, with the hydraulic motor type, specification. Both high speed, medium speed and low speed motor for nr., in some engineering applications, usually want to consider the lowest stable speed topic, not just for low speed high torque hydraulic motor.
5. 5 ~ 15% nr under low speed area is low efficiency area, at present there are few research; Conventional hydraulic motor performance test only study various efficiency more than 25% of the rated speed speed characteristics. In fact, in low speed region, leakage of hydraulic motor and the torque loss properties and more than 25% nr speed zone is completely different.
In the low speed region, Qmc decreases with the decreasing of the motor speed nm, is almost constant: Tmf rather than decreases with the decreasing of nm, which increases, and in the nm 50 or less increase faster when r/min, namely "negative damping" stronger. So, the motor at low speed area the Qmc and Tmf characteristics must be one of the main factors influencing the nmmin hydraulic motor.
6. Since the lowest stable speed nmmin hydraulic motor is refers to the long time continuous smooth running at low speed, only allow smaller speed fluctuating, so, the mathematical equation of the minimum stable speed, should be given priority to with the static governing equations of the external load should also be static load torque Tm, due to the inertia load under constant speed rotation at low speed is not at the top of a plus.
Second, the determinants of the lowest stable speed of hydraulic motor, hydraulic motor as power hydraulic system lowest stable speed of executive element, the nmmin value, mainly from the following six factors
1. The system adopts the hydraulic motor at low speed area leakage flow Qmc Tmf characteristic features and internal friction torque loss.
2. The system of the pump flow control device, control valve, flow valve control valve. Control,... . Small traffic required flow relative to the motor at low speed area. The output of the flow characteristic. It affects the working flow characteristic motor speed regulation equation.
3. Drag or control by the system. The load characteristic of the object. It affects the Qmc, Tmf characteristics of motor and speed regulating device work flow characteristic.
4. The control mode of the system, such as the open-loop system and closed-loop servo system, etc. It affects the ripple at low speed area automatically adjust the speed characteristics.
5. The system model of the hydraulic oil used and the oil temperature and its change at work. It affects the Qmc, Tmf characteristics of motor and speed regulating device work flow characteristic.
6. Hydraulic source and the main components of the system the overflow valve, direction valve, etc. Characteristics. It affects the working flow characteristic.
, therefore, to determine the hydraulic motor nmmin can't from the hydraulic motor in the low speed characteristics to determine itself, leaving the other five factors can determine the minimum stable rotating speed of hydraulic motor.
The above content is provided by the hydraulic co., LTD. Ningbo hengtong summary about the classification of the hydraulic motor, more knowledge about the hydraulic motor can seek advice at www.helmtower.com