The working principle of the door closer is when the door is opened, the door body drives the connecting rod to move, making the transmission gear rotate, and drives the rack plunger to move to the right. During the right movement of the plunger, the spring is compressed, and the hydraulic oil in the right chamber is also compressed. The one-way valve ball on the left side of the plunger is opened under the action of oil pressure, and the hydraulic oil in the right cavity flows into the left cavity through the one-way valve. When the door opening process is completed, since the spring is compressed during the opening process, the accumulated elastic potential energy is released, and the plunger is pushed to the left to drive the transmission gear and the door closer connecting rod to rotate, so that the door is closed.

During the spring release process, due to the compression of the hydraulic oil in the left chamber of the door closer, the one-way valve is closed, and the hydraulic oil can only flow out through the gap between the casing and the plunger, and pass through the small hole on the plunger and the 2 The flow passage equipped with the throttle spool returns to the right chamber. Therefore, the hydraulic oil constitutes a resistance to the release of the spring, that is, the buffering effect is achieved through throttling, and the speed of the door closing is controlled. The throttle valve on the valve body can be adjusted to control the variable closing speed of different stroke sections. Although the structure and size of door closers produced by different manufacturers are different, the principle is the same.

The types of door closers can be divided into: surface mounted and built-in top door closers, built-in door middle door closers, door bottom door closers (floor springs), vertical door closers (built-in automatic reset hinges) ) and other types of door closers.