Compression braking device of four-stroke cycle internal combustion engine

The invention provides a compression braking device of a four-stroke cycle internal combustion engine. A control valve mechanism (13) and a clearance compensation mechanism (23) with the compensated clearance being the lift range of a braking projection are installed in parallel on one end of an amounting elephant feet of a rocker (3); a clearance compensation mechanism (11) with the compensated clearance being the lift range of a valve clearance is arranged in the midpoint of the connecting positions of an exhaust valve bridge (5) and two exhaust valves (6); the elephant feet (24) are coaxially connected below the lower end of the previous clearance compensation mechanism (23); the upper end of the next clearance compensation mechanism (11) is always in contact with the lower ends of the elephant feet; and the spring force of the clearance compensation mechanism is smaller than braking oil pressure and larger than dead weight of the elephant feet. Compared with the prior art, the compression braking device improves the reliability and the balance of a valve actuating mechanism, simplifies the structure, reduces the processing difficulty of the rocker, improves the rigidity of the rocker, and improves the accuracy and operability of the adjustment of the valve clearance. In addition, when the engine compresses and brakes, the two exhaust valves can be opened at the same time, thereby improving the braking effect of the engine.