Analysis and Test of Controllable Hydro-pneumatic Springs
Nowadays people are also researching and developing shock absorbers for other principles, such as magnetorheological dampers and electrorheological dampers. However, these shock absorbers are complex in structure and costly, and it is difficult to obtain practical applications. The oil-gas spring is safe and reliable because of its good ride comfort. It has been widely used in many high-class passenger cars, and the adjustable oil-air spring is now widely used in armored vehicles to improve the smoothness of armored vehicles. The valve opening speed and valve opening pressure of the gas spring. For the adjustable oil-air spring, when the speed of the oil-air spring reaches a certain value, the bypass valve of the adjustable oil-gas spring is opened, and the flow volume of the bypass valve will affect the speed characteristics of the adjustable oil-air spring. Therefore, in order to To properly research, design, and develop an adjustable oil-air spring that meets the requirements of actual speed characteristics, the flow of the bypass valve of the adjustable oil-gas spring must be studied. The schematic diagram of the structure of the oil-gas spring and the structure of damping force The oil-gas spring has a floating piston in the piston rod. The floating piston divides the volume of the piston rod into two parts. The upper part is the air chamber of the oil-air spring, and the gas filled with certain pressure (nitrogen The lower part is in communication with the lower chamber of the oil-gas spring. Its structure is as shown. Pressure resistance When the hydro-pneumatic spring is in the static equilibrium position, the pressure in the air chamber, the pressure in the upper chamber and the lower chamber are equal, and the air chamber is back pressure. At this time, the product of the back pressure of the air chamber and the area of ​​the piston rod == the schematic diagram of the structure of the oil and gas spring is equal to the weight of the single wheel spring of the vehicle, ie, the initial inflation pressure of the air chamber; S is the area of ​​the piston rod; Wheel spring mass; gravity acceleration. When the oil-gas spring moves with certain rules, the damping of the oil-air spring is composed of three parts. The first part is the throttling damping force produced by the throttling of the oil; the second part is the damping caused by the pressure difference of the air chamber; Partially due to inertial forces generated by the piston movement. The resistance of the hydro-pneumatic spring is analyzed by two strokes of tension and compression. Compression resistance When the piston compresses, the compression resistance of the oil-gas spring is therefore. The total resistance of the oil-gas spring during the movement is the sum of throttling damping force, air chamber resistance and inertial force. The resistance of the air chamber is related to the movement position of the piston rod. The damping force of the throttle is related to the movement speed of the piston rod. The inertia force is related to the acceleration of the piston rod.
The damping force of throttling is known from the composition of the resistance. Regardless of the recovery or compression stroke, the throttling damping force is described by the above formula. The throttling damping force of the hydrostatic spring is equal to the throttling pressure difference and the internal diameter of the oil-gas spring cylinder and the piston rod. The product of the ring area is independent of static pressure and other areas. The size of the throttling damping force depends only on the piston speed and is independent of the position and acceleration of the piston. The bending deformation of the throttle valve is related to the throttling pressure difference, but not to the pressure difference and inertia force of the air chamber. The rectangular throttle plate structure and the structure of the bending deformation throttle plate can be used for the throttle plate according to the different structures and requirements of the gas spring. The throttle plate with different structures is adopted. As shown in the figure, the rectangular throttle oil and gas is used. Rectangular Spring Throttle Pieces Structure Diagram The working principle of the rectangular throttle piece oil spring is that when the speed is lower than a certain value, the hydraulic pressure cannot open the rectangular throttle plate, and the oil flow often passes through the throttle to open the throttle. Flow effect; When the speed reaches a certain value to increase the pressure of the oil to a certain value, the rectangular throttle valve is opened, and the oil flows through the throttle area formed by the opening of the rectangular throttle valve. Throttling, damping The size of the force is related to the maximum bending deformation of the rectangular throttle plate. The mechanical model of the rectangular throttle plate For the rectangular throttle plate of the oil-air spring, the arc at both ends is simplified as a straight line. Since the width is equal and the cross-sectional area is equal, it can be regarded as one end fixed and the other end free. Sectional rectangular cantilever beam, as shown. The throttling valve is subject to the throttling pressure difference; the throttling gap is the change in the length of the rectangular throttling valve; the maximum bending deformation of the throttling valve) The rectangular throttling valve mechanical model When the rectangular section When the throttle plate is subjected to a uniform throttling pressure difference, the throttle plate will bend and deform. When the relative movement speed of the oil-air spring changes, the throttling pressure difference on the valve plate will change, therefore, the throttle valve The opening will change with the throttling pressure difference. The equation of the bending deformation curve of the rectangular throttle plate is set as the width of the rectangular throttle plate, one end is fixedly restrained, one end is the free end, and the total length of the rectangular valve plate (that is, the height of the rectangle) is for the rectangular section tractor and agricultural transport vehicle flow The bending deformation of the valve plate is analyzed and calculated. The center of the fixed end is used as the origin, and the perpendicular line of the fixed end line is the x-axis, and the edge of the fixed end is used as the axis to establish the rectangular coordinate system.
The moment at any position is the torque of the right throttle plate to the x position. The force received is the product of the area of ​​the right rectangle and the surface uniform pressure load, that is, the throttling pressure difference, the force The point of action is the center of gravity of the rectangle. The moment of the rectangular throttle plate at the position where the throttle plate cross-sectional width is, the thickness is, then the moment of inertia at the place is when the rectangular throttle plate is uniformly distributed on the surface. When the load is applied, the throttle plate will be bent and deformed, and the amount of bending deformation at different positions will be different. Therefore, the throttle plate will be bent into a curved surface, and a bending deformation curve will be formed on the midline. The equation of the bending deformation curve is Among them, the elastic modulus of the material, and the integral constant, can be determined using boundary conditions. Therefore, the equation of the bending deformation curve of the rectangular throttle plate is the maximum bending deformation of the rectangular throttle plate with the maximum bending deformation of the rectangular throttle plate. That is the amount of bending deformation of the rectangular throttle plate at the free end. It can be known from the equation of the bending deformation curve of the rectangular throttle plate that the maximum bending deformation of the rectangular throttle plate is the rectangular throttle valve at that time. The numerical solution of the bending deformation curve of the piece can obtain the maximum bending deformation of the rectangular throttle piece. Opening and closing pressure of oil and gas springs and valve opening pressure of oil and gas springs When the bending deformation of the throttle plate reaches the thickness of the throttle plate, the oil and gas spring valve is opened. Using the bending deformation formula of the throttle plate, it can be calculated The valve opening pressure is the valve opening speed of the oil and gas spring. When the bending deformation of the throttle plate reaches the thickness of the throttle valve, the oil spring valve opens, according to the relationship between the maximum flow rate of the oil and gas spring and the valve opening pressure, and the continuity of the oil. Theorem of sex can be obtained so the valve opening speed is the area between the inner diameter of the cylinder spring and the piston rod; the inner diameter of the piston cylinder; the outer diameter of the piston rod; the opening pressure of the oil and gas spring; The area; for the flow coefficient; for the oil density. Flow rate before the valve opening of the oil gas spring When the bypass valve is not opened, the bypass valve does not flow through the oil. The oil passes through the oil-gas spring, and the flow rate through the oil-gas spring can be obtained according to the relationship between the flow rate and the velocity. The relationship between the speed and flow rate of the gas spring is the maximum flow rate when the bypass valve is opened. The maximum valve opening speed of the oil and gas spring When the bypass valve is opened, the constant throttle of the oil-gas spring remains inconvenient, but the flow rate changes, so damping occurs. The ratio has also changed, and the valve opening response has also changed. When the bypass valve is not opened, the damping force of the oil-gas spring when the valve is opened is the natural frequency of the hydro-pneumatic suspension system; it is the damping ratio of the suspension system before and after opening the bypass valve. Since the thickness of the oil spring spring valve plate has been determined, the valve opening pressure before and after the bypass valve is opened remains constant, that is, the maximum valve opening speed of the oil gas suspension system after the bypass valve is opened. After the valve is opened, the relationship between the pressure and flow rate of the oil-gas spring can obtain the maximum flow rate when the oil-gas spring is opened. This is the maximum valve-opening pressure of the oil-gas spring after the bypass valve is opened; it is the maximum of the oil-gas spring after the bypass valve is opened. flow. The maximum flow rate of the bypass valve is based on the relationship between the flow rate of the bypass valve, the flow rate of the constant orifice of the oil and gas spring, and the total oil and gas displacement of the oil and gas spring. The bypass valve, designed for maximum flow through the valve, acts as a bypass valve for controllable hydro-pneumatic springs. By controlling the current, the flow of the bypass valve is controlled so as to control the resistance characteristics of the oil-gas spring. Under different control currents, the resistance characteristics of the designed controllable hydro-pneumatic springs are tested. The test results are as shown.
The design of the throttle valve of the adjustable throttle valve piece for the oil-gas spring The flow chart of the oil and gas spring for the control of the current is known from the dynamometer diagram obtained through the experiment. It can be seen that the flow of the bypass valve can control the resistance of the controllable oil-gas spring through the flow of the bypass valve. Characteristic control. Conclusion Through the analysis and test of controllable hydro-pneumatic springs, it can be known that there are three parts of the oil-gas spring resistance, namely throttling damping force, air chamber resistance and inertial force, which are related to the speed, position and acceleration of the hydro-pneumatic spring. The size of the throttle damping force is related to the annular area between the piston rod of the gas spring and the inner diameter of the cylinder of the oil-gas spring. With the bypass valve open, the valve opening speed of the oil and gas spring is related to the designed damping ratio of the oil-gas spring. The by-pass valve flow affects the damping characteristics of the oil-air spring. Therefore, the design and control of the bypass valve flow can be achieved to achieve the design and control of the damping characteristics of the adjustable oil-air spring.
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