Key points of throttle valve
Key points of throttle valve
1. Application of throttle valve
Throttle valve is often used in oil supply throttle speed regulation hydraulic system with little load change or low requirements for speed control accuracy. Sometimes it is also used in volume throttle speed regulation hydraulic system with variable pump oil supply.
(1) Series throttle speed regulation. Connecting the front of the inlet and the rear of the outlet of the actuator in series, or connecting a throttle valve in series before the inlet and after the outlet, can form an inlet throttle speed regulating circuit, an outlet throttle speed regulating circuit or an inlet and outlet throttle speed regulating circuit. Figure 81 (a) shows the inlet throttle speed regulation circuit. Since the throttle valve is connected in series in front of the electromagnetic directional valve, the reciprocating motion of the piston belongs to the oil inlet throttle speed regulation process. The one-way throttle valve can also be connected in series on the oil circuit of the directional valve and the oil inlet chamber of the hydraulic cylinder to realize one-way oil inlet throttle speed regulation. For the throttle speed regulating circuit of the oil inlet circuit, since the throttle valve and the overflow valve are connected in parallel, the flow into the hydraulic cylinder (excess oil returns to the oil tank through the overflow valve) can be controlled by adjusting the size of the throttle valve port to achieve the purpose of speed regulation. According to the characteristics of the oil inlet throttle speed regulating circuit, the oil inlet throttle speed regulating circuit of the throttle valve is suitable for occasions with low speed, light load, little load change and low requirements for speed stability.
Figure 81 (b) shows the outlet throttle speed regulation circuit. Since the throttle valve is connected in series on the oil return path between the electromagnetic directional valve and the oil tank, the reciprocating motion of the piston belongs to the oil return throttle speed regulation process. The return oil flow of the hydraulic cylinder is adjusted through the throttle valve to control the flow into the hydraulic cylinder. Therefore, the purpose of speed regulation can be achieved as the throttle speed regulation circuit of the oil inlet circuit.
Figure 81 (c) shows the inlet and outlet throttle speed regulation circuit.
(2) Parallel (bypass) throttling speed regulation. The throttle speed regulating circuit of bypass oil circuit is to set the flow control valve on the branch circuit with parallel actuators, as shown in Figure 82. The throttle valve is used to adjust the oil flow back to the oil tank, so as to indirectly control the flow into the hydraulic cylinder, so as to achieve the purpose of speed regulation. The circuit is normally closed and plays the role of safety protection. Therefore, the oil supply pressure of the hydraulic pump changes with the load.
The throttle speed regulation of bypass oil circuit is suitable for high-speed and high-power occasions with small load change and low requirements for motion stability. It should be noted that in this speed regulating circuit, the leakage of the hydraulic pump has a greater impact on the speed of piston movement, while in the oil inlet and return throttling speed regulating circuit, the leakage of the hydraulic pump has less impact on the speed of piston movement, so the speed stability of this speed regulating circuit is lower than that of the first two circuits.
(3) The actuator decelerates. Fig. 83 shows an actuator deceleration circuit using a travel deceleration valve. When the two position four-way directional valve 4 is switched to the left position, the pressure oil of the hydraulic pump l enters the rodless cavity of the hydraulic cylinder 6, and the piston moves quickly to the right. The hydraulic cylinder discharges oil to the oil tank through the travel throttle valve 5 and the directional valve 4. When the piston reaches the specified position, the stop 7 gradually presses down the travel throttle valve 5 to slow down the movement of the piston until the throttle port of the valve 5 is completely closed. At this time, the return oil of the hydraulic cylinder is drained to the oil tank through the throttle valve in one-way throttle valve 3. The speed of the hydraulic cylinder is determined by the opening of throttle valve 3. When there is a one-way valve in the hydraulic cylinder 4 and the hydraulic cylinder 4 in the figure, the oil is returned to the position of the check valve in the hydraulic cylinder 4 through the quick change-over valve in the hydraulic cylinder 4. The circuit structure is simple, and the deceleration stroke can be realized by adjusting the position of stop 7.
(4) Actuator buffer. Figure 84 shows the actuator buffer circuit with one-way travel throttle valve. The inlet and outlet oil circuit of the double rod hydraulic cylinder is equipped with one-way travel throttle valve 4 and valve 5. When the two position four-way directional valve 3 works on the left, the pressure oil of hydraulic pump 1 enters the left chamber of the hydraulic cylinder through the one-way valves of valve 3 and valve 4, the oil in the right chamber returns through the travel throttle valve in valve 4, and the piston rod moves to the right. When the travel of the hydraulic cylinder is close to the end of the right end, The movable stop 8 moving with the piston rod gradually presses down the travel throttle valve in the valve 5 until it is closed, so that the speed of the hydraulic cylinder gradually slows down until it stops gently, so as to avoid the end impact and achieve the purpose of buffering. The buffering of the hydraulic cylinder when moving to the left is realized by the one-way travel throttle valve, and the working principle is the same as that when moving to the right.
2. Precautions for use
(1) For the import and export of ordinary throttle valves, some products can be adjusted arbitrarily, but some products can not be adjusted. When using them, they should be connected to the system according to the product instructions.
(2) The throttle valve should not work at a small opening, otherwise it is easy to block and cause the actuator to crawl.
(3) The throttle valve and one-way travel throttle valve shall be fixed on the machined base surface of the travel stop path with screws, and the installation direction can be determined according to needs; The stroke and inclination of the stop or cam shall be made according to the product description and shall not be too large.
(4) The throttle opening shall be adjusted according to the speed requirements of the actuator and locked after adjustment to prevent loosening and changing the adjusted throttle opening.
