A valve mechanism , comprising: a valve having a valve roller ; a camshaft provided with a cam ; an intermediate swing arm located between the cam and the valve , the cam driving the valve to move by means of the intermediate swing arm , and the intermediate swing arm having an intermediate swing arm roller ; a lift regulating mechanism and a roller assembly , wherein the lift regulating mechanism comprises an eccentric wheel , the roller assembly is supported by the cam , the eccentric wheel and the intermediate swing arm roller , the lift regulating mechanism is configured to variably regulate a lift of the valve continuously, a peripheral surface of the eccentric wheel comprises a lift regulating section having a start point and an end point, a maximum lift point of the lift regulating section is located between the start point and the end point, the lift regulating section is divided into a first section from the start point to the maximum lift point and a second section from the maximum lift point to the end point, the first section is configured as a convex arc, at least a part of the second section is an oblique line section and/or a concave arc, and a distance between any point on the at least a part of the second section and an rotation axis of the eccentric wheel is less than a distance between the maximum lift point and the rotation axis of the eccentric wheel , wherein when the eccentric wheel is located at a maximum lift position, the roller assembly is movable on a cambered surface of the eccentric wheel , and a radius of a movement track of the roller assembly is less than a radius of the eccentric wheel at the maximum lift point, such that a range of the movement track of the roller assembly is an area where a pressure angle is greater than a frictional angle of a profile of the eccentric wheel , the eccentric wheel is subjected to a resultant force having a direction passing through a center of the eccentric wheel , and the eccentric wheel is self-locked. a valve having a valve roller ; a camshaft provided with a cam ; an intermediate swing arm located between the cam and the valve , the cam driving the valve to move by means of the intermediate swing arm , and the intermediate swing arm having an intermediate swing arm roller ; a lift regulating mechanism and a roller assembly , wherein the lift regulating mechanism comprises an eccentric wheel , the roller assembly is supported by the cam , the eccentric wheel and the intermediate swing arm roller , the lift regulating mechanism is configured to variably regulate a lift of the valve continuously, a peripheral surface of the eccentric wheel comprises a lift regulating section having a start point and an end point, a maximum lift point of the lift regulating section is located between the start point and the end point, the lift regulating section is divided into a first section from the start point to the maximum lift point and a second section from the maximum lift point to the end point, the first section is configured as a convex arc, at least a part of the second section is an oblique line section and/or a concave arc, and a distance between any point on the at least a part of the second section and an rotation axis of the eccentric wheel is less than a distance between the maximum lift point and the rotation axis of the eccentric wheel , wherein when the eccentric wheel is located at a maximum lift position, the roller assembly is movable on a cambered surface of the eccentric wheel , and a radius of a movement track of the roller assembly is less than a radius of the eccentric wheel at the maximum lift point, such that a range of the movement track of the roller assembly is an area where a pressure angle is greater than a frictional angle of a profile of the eccentric wheel , the eccentric wheel is subjected to a resultant force having a direction passing through a center of the eccentric wheel , and the eccentric wheel is self-locked. <EOS>