The basic components of a hydraulic door closer include a support guide, transmission gear, return spring, check valve, rack and pinion plunger, throttle valve core, housing, end cap, sealing ring, and connecting rod. The housing and connecting rod serve to fix the door closer and connect the door leaf and door frame.
The working principle of the door closer is as follows: When the door is opened, the door body drives the connecting rod, which in turn rotates the transmission gear, driving the rack and pinion plunger to the right. During the plunger's rightward movement, the spring is compressed, and the hydraulic oil in the right chamber is also pressurized. The check valve ball on the left side of the plunger opens under oil pressure, and the hydraulic oil in the right chamber flows to the left chamber through the check valve. When the opening process is complete, the elastic potential energy accumulated during the spring compression is released, pushing the plunger to the left, driving the transmission gear and the door closer connecting rod to rotate, thus closing the door.
During spring release, the hydraulic oil in the left chamber of the door closer is compressed, the one-way valve is closed, and the hydraulic oil can only flow out through the gap between the housing and the plunger, and then return to the right chamber through the small hole on the plunger and the two flow channels equipped with throttle valve cores. Therefore, the hydraulic oil creates resistance to spring release, achieving a buffering effect through throttling, thus controlling the door closing speed. The throttle valve on the valve body is adjustable, allowing control of varying closing speeds at different stroke stages. Although door closers from different manufacturers may differ in structure and size, the principle is the same.