Variable Valve Mechanism for Internal Combustion Engine

A variable valve mechanism for an internal combustion engine, comprising:

• a variable mechanism for varying a maximum lift amount of a valve according to an angular position of a control shaft;
• and
• an actuator connected to the control shaft via a worm gear mechanism, the variable valve mechanism varying the maximum lift amount of the valve by rotatably driving the control shaft via the worm gear mechanism using the actuator;
• wherein the worm gear mechanism includes a worm gear connected to the actuator and a worm wheel connected to the control shaft;
• wherein the worm wheel has teeth that are in mesh with the worm gear over a predetermined angular range including a required rotational range of the control shaft and is formed to be brought out of mesh with the worm gear outside the predetermined angular range;
• wherein the required rotational range of the control shaft includes an angular range of the control shaft ranging from an angular position that corresponds to a minimum setting value of the maximum lift amount of the valve to an angular position that corresponds to a maximum setting value thereof;
• and
• wherein the predetermined angular range is set such that, when the control shaft rotates in a small lift direction to exceed the angular position associated with the minimum setting value, the worm wheel and the worm gear are brought out of mesh with each other before the maximum lift amount of the valve reaches a minimum limit value required for achieving a marginal amount of intake air that allows an optimum operating condition of the internal combustion engine to be maintained.

A variable valve mechanism for an internal combustion engine, comprising:

• a variable mechanism for varying a maximum lift amount of a valve according to an angular position of a control shaft;
• and
• an actuator connected to the control shaft via a worm gear mechanism, the variable valve mechanism varying the maximum lift amount of the valve by rotatably driving the control shaft via the worm gear mechanism using the actuator;
• wherein the worm gear mechanism includes a worm gear connected to the actuator and a worm wheel connected to the control shaft;
• wherein the worm wheel has teeth that are in mesh with the worm gear over a predetermined angular range including a required rotational range of the control shaft and is formed to be brought out of mesh with the worm gear outside the predetermined angular range;
• wherein the required rotational range of the control shaft includes an angular range of the control shaft ranging from an angular position that corresponds to a minimum setting value of the maximum lift amount of the valve to an angular position that corresponds to a maximum setting value thereof;
• and
• wherein the predetermined angular range is set such that, when the control shaft rotates in a large lift direction to exceed the angular position associated with the maximum setting value, the worm wheel and the worm gear are brought out of mesh with each other before the maximum lift amount of the valve reaches a maximum limit value that can prevent a collision between the valve and a piston.