In 2000, the application of hydraulic pneumatic and sealed pressure relay in the position detection of hydraulic cylinders was carried out by Zhu Baojingguan, and the method of verifying the moving position of the hydraulic cylinder piston rod in the hydraulic circuit was verified by the specific practice. Mostly, the travel switch is used, that is, the mechanical structure connected to the piston rod of the cylinder is used to trigger the travel switch of different installation positions, thereby picking up the electrical signal of the corresponding position; but in some cases, the stroke switch is directly connected with the piston rod. The mechanical structure can not be installed at all, and even the position of the travel switch is not installed. In this case, it is conceivable to replace the travel switch with a pressure relay. The body method is the movement position of the piston rod, the outer wall and the piston rod to be taken out. Correspondingly, a small hole is drilled, and a reactive pressure relay is connected from the hole. After the piston runs through the hole quickly, the pressure relay can react to the pressure change of the hole from the rod cavity to the rod cavity, thereby The electrical signal is sent, and the function of the travel switch is limited. The text is only for differential. In the state, the pressure difference between the two chambers of the hydraulic cylinder is calculated, and the effective working area of ​​the rodless cavity of the hydraulic cylinder that takes out the position of the piston rod of the hydraulic cylinder by the pressure relay under the working condition is analyzed; the hydraulic cylinder has the rod cavity △ △ 2, the total loss of local taste loss on the pipeline; 12 pipelines connected to the rod chamber of the cylinder without the rod cavity, the pump hydraulic valve at the intersection of the oil return valve and the oil return valve have a rod cavity and a rodless cavity The pressure difference can be part of the pressure loss. The size of the price changes with the structure of the first line. Here, in order to analyze the turbulent state, the value needs, right, the factory 2 can not make a specific calculation but in other cases, the empirical formula can be listed. Calculation = 乜, by Darcy, 3 formula, the pressure loss along the path in the round pipe 1 differential movement; the pressure difference between the two chambers of the pressure cylinder is calculated according to the smooth circular pipe oil channel, if all cases are not considered The leakage differential velocity and the resistance coefficient along the path are related to the Reynolds number, and the flow state of the tube is (4). The average flow velocity in the round tube of the formula (2) is rounded, 138; the inner diameter of the tube; the kinematic viscosity of the fluid, when 1 Heart 1. When the hydraulic light is turbulent along the pipe, due to the flow rate of the pipe 3, Therefore, the formula 6 becomes the coefficient of strength along the path of the formula 12 into the formula 5; the heart, the two characters are included; the input 2 is determined according to the size of only 6 values ​​calculated in the formula 7. 89 or; the object 3 cylinder is placed vertically, the type 13 is still found 2 through the example to calculate and verify the 7-foot line supporting hydraulic system principle, 3 is the mainframe structure, the total flow of the main system dual pump discharge 563 liters汾; the integrated pipe valve block and the main cylinder connected to the two pipes in the case of the 2 inner diameter 21 in the differential state is the 4 power supply pressure difference according to the 1 formula 2 type 3 formula according to the 7 formula is obtained because only more than 3000 is less than Therefore, the flow pressure loss characteristic curve of the 9-way 40-diameter insert is found by the above calculation. 差3.802 in the differential state, and the characteristic curve of the pressure relay is found according to this value. It is found through the search that almost all the set pressures are 103. The following pressure relays have a difference between the sensitivity opening pressure and the closing pressure of less than 3.
80213, which means that the value in the differential state is sufficient to reliably cause a change in the state of the pressure relay.
In the example of the process requirements and verification process, the master cylinder needs to take out a position signal as required. 1 The master cylinder differential is quickly lowered by 14 inches and is equivalent to a position of 0.35 m1. 2 The position of the master cylinder to the bottom dead center, the position of the 3 master cylinders to the top dead center can be seen from the 3, the mechanical structure of the small cylinder live cold rod can not be installed, so that the master cylinder is lowered 14 The position of the electric double 4 of the inch position and the bottom dead center of the master cylinder to the top dead center cannot be taken out by the travel switch. By the calculation in 2 1 , the electric signal of the main cylinder falling 14 inches can be used in the differential relay. It is taken out in the circuit, and according to the pressure of the master cylinder during the extrusion process, the pressure is constant at 1313 or less, and the set pressure of the pressure relay 33 for taking the top dead center of the upper and lower dead center electric appliances is determined at 18, 5 or more. Therefore, in the hydraulic pressure, the external bullying and the 14-inch corresponding position drill holes and three pressure relays 40 people 10100220; 3 decay 3 coincidence, placed in the tube with the rod chamber of the liquid-flavored cylinder without rod cavity On the road, in order to make the change 1 art convenient, the programmable controller is used in the electrical control. (3) When the person is debugging in the field, the hydraulic circuit is operated in the sway state by manual operation, and the pressure relay 3 is repeatedly adjusted to make the hydraulic cylinder piston. Before and after the 14 inch point The three normally open contacts are changed from the suction to the disconnection, and the operating pressure of the 3rd and 3rd is adjusted. Then, after the system is under the control of the test, the test results are sub-successful. Tests were carried out, and when the 6 energized piston passed, the joint was not issued with a double. 4 When the power is turned off and the pressure of the back pressure relief valve is applied, after the piston passes through the 51 contact point, 5 sends a 屯 signal. This differential differential unloaded fast operation and the differential pressure calculation of the loaded load without load and quick return After the analysis and introduction, this fully confirms the feasibility of taking the electric signal by the pressure relay instead of the travel switch during the fast running process.
3 problems to be noted 3.1 The designer decides whether to use a pressure relay instead of the hall switch. It is necessary to make a detailed calculation for 9. If the example is reduced, the diameter of the piston rod is thickened, the diameter of the selected insert is increased, and the diameter of the differential pipe is increased. The value of 4 calculated by the formula 13 may be very Small postal sensitivity + enough to cause the action can not replace the travel switch with a pressure relay.
3.2 In the example, the pressure relay 3矸 changes the relay pull-in state when non-differential operation and return trip are detected under various working conditions, and the signal that is useful to us is in the differential phase, so when drawing the electrical trapezoid and programming Within the differential section of Xu, the effect is effective. In addition, the signals of 51 in other stages are treated as special effects. Hydraulic Engineering Manual. Beijing Machinery Industry Press, 1990 2 Guan Zhongfan. Hydraulic drive system. Beijing Machinery Industry Press, 1989 3 Jinan Foundry and Forging Machinery Research Institute. Through the same media with the author Zhu Baojing, male, engineer, Jinan Hydraulic Parts Factory hydraulic technology research and development date 1999
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