VARIABLE VALVE TRAIN

PROBLEM TO BE SOLVED: To provide a variable valve train which promptly raises the temperature of hydraulic fluid, provides stable variable operation immediately after starting an engine, and prevents an excessive temperature rise. SOLUTION: This variable valve train 1 includes: a spring 11 urging a valve 10 as an intake valve or an exhaust valve in a valve closing direction; a cam 12 pressing the valve in a valve opening direction against the pressing force of the spring; a piston 19 connected to the valve; a control room 21 for inserting the piston; and a control unit 24 changing valve closing timing by controlling the introduction/discharge of the hydraulic fluid into/from the control room. In the variable valve train, the middle of a discharge line 25b for discharging the hydraulic fluid from the control room and the middle of an introduction line 25a for introducing the hydraulic fluid to the control room are connected to each other through a short-circuit line 3, and a thermostat 4 opened at a predetermined temperature or higher and closed below the predetermined temperature is provided in the discharge line downstream of a connection point 3b between the short-circuit line 3 and the discharge line 25b. COPYRIGHT: (C)2011,JPO&INPIT