The present invention relates to a valve 
train mechanism and a 
fuel supply system of 
internal combustion engine, and particularly relates to an oil control device of a hydraulic fully variable valve 
system of the 
internal combustion engine. This device connected with the hydraulic valve 
system of 
internal combustion engine, the device consists of a housing, a 
rotary valve, a 
hydraulic accumulator and a transmission mechanism. The 
rotary valve, the 
hydraulic accumulator and the transmission mechanism are installed in the housing. The 
rotary valve consists of a rotary valve shaft and a rotary valve sleeve. The 
hydraulic accumulator consists of an accumulator 
piston, an accumulator spring, an end cover, a sealing seat ring and a rubber 
gasket and is installed in the cavity at one end of the housing. An accumulator chamber is provided between the rotary valve and the hydraulic accumulator. The transmission mechanism consists of a transmission gear, a gear shaft and a cross slide 
coupling. The transmission gear is installed on the gear shaft, while the gear shaft is connected with the rotary valve shaft through the cross slide 
coupling. The present invention can replace a high-frequency 
solenoid valve, it is applicable to use with hydraulic fully variable valve system of single-cylinder and multi-cylinder internal 
combustion engines. And the present invention has the advantages of simple structure, reliability, good manufacturability and low cost.