Patent ID: 6932051

Claim:
A throttle valve opening and closing device comprising: a throttle body for forming an intake passage led to an internal combustion engine; a throttle valve rotatably mounted in the intake passage formed by said throttle body and changing an opening area of said intake passage to reduce the opening area when a flow rate of intake air is to be reduced, and to increase the opening area when the flow rate of intake air is to be increased; a driving mechanism for driving said throttle valve to rotate such that, when said driving mechanism is operated in one direction, said throttle valve is rotated in one direction over an operating range; a single return spring for generating a biasing force to return said throttle valve to one end of a movable range of said throttle valve when said driving mechanism generates no driving forces; and an air passage defined by said intake passage and having a default position in which said throttle valve is located when a driving force form said driving mechanism does not act on said throttle valve, a position of a minimum opening area in which the opening area is minimized within the movable range of said throttle valve, and an operating range in which the opening area is gradually increased from the minimum opening area, the default position, the position of the minimum opening area and the operating range being formed in successive order in a rotating direction of said driving mechanism and said throttle valve.