The relief throttle valve is a pressure-compensated throttle valve, which is composed of a relief valve and a throttle valve connected in parallel. Part of the high-pressure oil at the inlet goes to the actuator through the throttle valve, and the other part returns to the tank through the overflow port of the relief valve (the smaller the amount of oil returned to the tank per unit time, the higher the inlet pressure, and vice versa. big). The upper and lower ends of the relief valve are connected with the pressure oil before and after the throttle valve respectively. When the outlet pressure increases, the valve core moves downward, closing the overflow port, and the overflow resistance increases, that is, the amount of oil returned to the tank decreases, and the inlet pressure increases accordingly. Therefore, the pressure difference before and after the throttle valve is basically maintained. unchanged; vice versa. That is, the flow rate through the valve is basically not affected by the load.