The invention discloses a compression releasing
engine braking method and device. A primary
piston hole and a secondary
piston hole connected with a hydraulic passage are formed in a valve bridge, and a primary
piston and a secondary piston in the piston holes are driven by using a braking lug boss of a
cam to open an
exhaust valve for braking. During braking, the retraction position of the primary piston is kept by using the equal altitude section of the braking
cam at the maximum braking lift, the hydraulic passage between the primary piston hole and the secondary piston hole is closed, and the braking load on the secondary piston is transferred to a braking bracket positioned on the valve bridge and is not returned to the primary piston. The primary piston is further driven by using an integrated exhaust lug boss on the
cam, the primary piston drives the valve bridge to move and is separated from the braking bracket, and an oil
discharge passage in the valve bridge is opened to
discharge oil, so that the secondary piston returns to the retraction position, and the braking exhaust door is moved to a closed position. A compression releasing braking mechanism is integrated with a traditional air valve driving chain, and the braking bracket bears the braking load and the weight braking
valve lift, so the braking load is reduced and the braking power is increased.