Image Number 17 for United States Patent #7118097.
A device for controlling a choke valve of a carburetor for an engine includes: a choke closed state hold device for holding, in a closing position, a choke lever urged by a spring in a direction for opening the choke valve, when the choke lever is turned to the closing position, the choke closed state hold device releasing the choke lever from the held state by a throttle operation thereafter performed; a control lever which turns between a low-temperature position and a high-temperature position, and which at its low-temperature position limits the position of the choke lever released from the choke closed state hold device to an intermediate position and at its high-temperature position limits the position of the choke lever to an opening position; a first control spring which urges the control lever toward the low-temperature position; and a second control spring which is made of a shape memory alloy, and which turns the control lever to the high-temperature position when the engine temperature reaches a predetermined high temperature. With this arrangement, the opening of the choke valve is controlled in a rational way according to changes in engine temperature, to thereby stabilize warm-up operation and improve the fuel consumption rate.
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