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.