On-line detection method for impact performance of hydraulic impact mechanism
2 Abstract The air pressure method which can be used for on-line testing of hydraulic impact mechanism performance is proposed, and the principles of sampling principle of the test system are elaborated.
1 Introduction How to accurately obtain the impact energy impact energy frequency in the impact process, not only is beneficial to the management and monitoring of the equipment, but also the hydraulic impact mechanism rock drill gravel electromechanical liquid hammer pile hammer and other turbulent decay water Bamboo is a problem that must be solved. At present, the output parameters of the impact mechanism are detected. Segmental stress wave method photoelectric method magnetic method, high speed, color method and energy method. However, these methods may be due to equipment limitations, or because of the high cost of material consumption and the inability to achieve solidification. Most of them are only used for performance testing of a product in the laboratory, and can not be used for on-line testing at the production site. This paper proposes a new impact mechanism test method for air pressure, which can easily realize on-line testing of impact performance.
2 Basic Principle of Air Pressure The air pressure method requires that the rear end portion of the piston that moves the impact mechanism be placed in a closed helium chamber with a fixed clamping force. The reciprocating motion of the piston during the impact process will not cause the gas state in the nitrogen chamber to be drawn, which is not only conducive to the test of the system pressure, but also facilitates the regular elimination of the air in the pipeline and reduces the hydraulic mountain caused by the air in the system. .
3 Conclusion Hydraulic shock is a problem of liquid unsteady flow in the pipeline, which is a dynamic process. Because of its many influencing factors, it is difficult to calculate with accurate methods. However, for the overall characteristics of the hydraulic system, deeper division, grasping the key points, and identifying various factors that may cause hydraulic shock, and taking necessary technical measures and related measures to solve the hydraulic system will be greatly reduced. Small or even partial elimination of hydraulic shock, avoiding movement, the heat in the air break is too late to exchange heat with the external enthalpy, and its state change can be regarded as an adiabatic process. The c between the gas pressure and the volume is the same as the constant barometric pressure method in the principle of the live 1 under the return stroke of the pressurized oil flow. At the moment, the effective area of ​​the piston is at the position of 1 especially. When the nitrogen pressure in the nitrogen chamber is still the product, the piston is in a wide position. At this time, the nitrogen pressure in the nitrogen chamber is 2 volumes of the plant. Fang Ke knows that the date of receipt of 2000226 is mainly engaged in scientific research work on hydraulic impact technology, which avoids excessive problems during system commissioning and operation, which is very important to ensure the normal operation of the hydraulic system.
Song Xueyi. Pocket hydraulic and pneumatic manual elbow. Beijing Machinery Industry Publishing y.W9K Zhang Liping, and so on. Hydraulic and pneumatic system design manual. Beijing Mechanics 3 Lu Wanglong. Practical hydraulic machinery troubleshooting and lending. , 1 Hu has Hunan Science and Technology Press. 1995.
It can be seen from the above formula that since the piston is displaced within the time of =21, it is known that the piston passes. The average speed of the separation between points is that the above type of burn can still be obtained by periodically sampling the nitrogen chamber pressure by a pressure sensor. When the sampling interval is small, the average speed can more accurately reflect the state of motion of the piston at this time.
After obtaining the moving speed of the piston, the values ​​of the series of piston motion speeds obtained from the piston calculated by the highest speed are compared, and the time at which two adjacent speed peaks are found, the absolute value of the difference is the piston period, and the impact frequency That is, if the reciprocal of the cycle is to change the trend of the piston violation period or the change trend of the nitrogen chamber gas cycle in the form of a curve. It can intuitively read the cold motion cycle, and calculate the frequency test system. The air pressure test system consists of the following basic parts. The square mU pressure sensor prints the nitrogen chamber and must be a closed cavity and filled with constant pressure. The nitrogen, fixed mass gas at a pressure higher than 4 cubits 3, its adiabatic state change can not be accurately reflected by the gas state equation 7 =. Need to make more complicated corrections 3. For the convenience of testing. accurate. Generally, the pressure value of the air chamber at the maximum return position is controlled to be 3.53.7.
This can be used to calculate the nitrogen chamber, the card force is live, the front end of the body is knocked, and the pressure at the position where the buffer chamber is located is eliminated.
The sealing of the nitrogen chamber is an important consideration. Sealing, poor performance not only causes test errors between two different state tests, but also affects the accuracy of the data during the same test.
The dynamic seal between the piston and the nitrogen chamber is a difficult point of sealing. The sealing method used not only requires good self-centering properties such as wear resistance, but also ensures high speed of the piston, 8, and the high temperature of the bearing.
In addition to (4), the fried rushing device and the liquid-gas combined impactor can be directly used for the test, and the pure hydraulic impactor of the factory said that an additional air cavity is required for the test. The air pressure of the air chamber should be as low as possible to ensure a good linearity of the air pressure change, so as to minimize the additional impact of the gas work on the impact energy. Of course, the impact energy value after the test needs to be corrected when the test accuracy is high.
The pressure sensor gas pressure is the only direct detection quantity in the air pressure method, so the measurement accuracy of the pressure sensor directly affects the test result. It is important to choose a pressure sensor with a suitable performance price.
The sampling system sampling system is a system mainly based on the weighing machine. It encapsulates the hardware and softens the analog electric signal output from the pressure sensor through the multiplexer switch and sends it to the human-speed amplifier for processing. 1 to convert. The start of the analog-to-digital converter can be started in the program start mode by the timer timing trigger start mode conversion state and the result can be queried and read by the program, and the conversion end signal informs the microcomputer or print forming in an interrupt manner. According to the basic principle of the air pressure method, the speed of the piston is the differential of the displacement versus time. The accuracy of the displacement is guaranteed by the accuracy of the pressure sensor and the 1 conversion tip. The accuracy of time must be guaranteed by precise timing triggering.
This function can be implemented by a timer or a programmable count timer in the microcontroller. In this paper, the 8253 programmable counting timer is used to accurately guarantee the sampling time. In the test, the working mode of the 8253 is set to the mode 2 ratio generator to ensure that the requirements of the human 0 conversion start signal are met. The 8253 timer channel selection principle is as follows: the reference clock 1 is added 2, and the duty ratio is 50. At 18 o'clock, the level timing channel should be selected. When the timing interval is greater than 65.535 muscle, the two-stage timing 5100 sampling time ms is allowed to convert. 1, 1 result to data processing 4 sampling period sampling frequency determination principle Determination of sampling period The test value of the impactor operating condition is less sampling point, the measured speed is the average speed can not accurately reflect the real motion state of the impact piston. The greater the piston speed, the greater the distortion, which is most severe near the strike point. In order to ensure the accuracy of data acquisition, there is no frequency mixing phenomenon. The sampling and the determination must first comply with the meter-like law. The sampling frequency must be higher than the frequency of the signal to be taken. The sampling period must take into account the sampling period of the sampling and the conversion device. The speed of conversion of the bit conversion chip, which is also commonly used, is about the same. In the single channel test, the sampling period must be greater than this value; the determination of the sampling period must consider the movement speed of the piston. In the air chamber experiment, the oscillating magnetic method and the illuminating test are used to test the impact energy, and the relative error of the test results. Less than 5, this shows that the test results have higher reliability.
6 Conclusion Compared with the traditional test method, as a non-contact air pressure method, it has good vibration resistance and a small workload. It can simultaneously measure impact energy and impact frequency. Calibration is convenient for impact parameter error and high accuracy. It can be used not only as a measurement and identification method for products in the laboratory, but also for easy online testing in wide-text work. This traditional test method is unmatched. The barometric method can be given to the actual. The monitoring of each state is set in the production process. Management and maintenance bring great convenience.
1 Guo Xiaoxian. Wait. Rock drilling machine impact energy and its test method rock drilling machinery pneumatic tools 19941.
2 Northeastern Institute of Technology mechanical parts design manual writing group. Mechanical parts design procedures hydraulic transmission and pneumatic transmission elbow Beijing Metallurgical Industry Publishing f.b1979.
For; to connect with China; anti-body transmission and control field information and technology flow. To promote the development of technology in this academic field, the Fluid Power Transmission and Control Branch of the Institute of Mechanical Engineering is scheduled to hold the first Xuemu Conference in Ningbo, Zhejiang Province from August 8 to August 20, 2, and welcome experts and scholars to work. Technical personnel and production managers enthusiastically contribute to the exchange of details. Hydraulic and pneumatic magazines 2, 1 year 8th 1f, the channel is used in series to complete.
Sampling box 3.
Set, the address definition array degree 1 coffee 253 control Yu set time 膈 2 start 1 test before and after 2 times the sampled pressure difference is greater than the pressure sensor error value to ensure that the result calculated by Equation 3 is accurate, otherwise, test The curve will be random.
5 measured shape when testing the example. It can be seen that the maximum impact velocity of the piston is 5.82 and the impact frequency is 2.5. The piston's various motion state strokes return speed return stroke deceleration shock rebound is very clear.
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