Thermostatic valve for compensating air fuel mixture for air temperature change

In an internal combustion engine having:

• a carburetor supplying an air fuel mixture to said engine through an intake pipe, said carburetor having a float chamber for storing fuel and a throttle valve for adjusting amount of air flow, and an air cleaner connected at the upstream side of said carburetor and supplying the air to said carburetor through a filter element, said air cleaner having an intake air passage to introduce the air from atmosphere, and a temperature responsive system comprising:
• a change-over valve pivotally mounted in said intake air passage adjacent to an aperture formed in said intake air passage for closing and opening the same, a vacuum motor mounted on said intake air passage and having a vacuum chamber and a movable diaphragm responding the vacuum applied to said chamber, said diaphragm being connected to said change-over valve so that said change-over valve is actuated to close and open said aperture in response to the movement of said diaphragm, a conduit connected to said aperture at one end and opening to a portion of an exhaust pipe so as to introduce warmed air around said exhaust pipe into said air cleaner when said aperture is opened, and a thermostatic valve mounted in said air cleaner for changing over a plurality of passages in response to temperature of intake air;
• said thermostatic valve comprising:
• a temperature detector having a thermally expandable member adapted to expand and shrink in response to the temperature of said intake air and an operation shaft adapted to be actuated by said thermally expandable member;
• a housing to which said temperature detector is attached, said housing having a first port communicating with the atmosphere, a second port communicating with said vacuum motor, a third port communicating with the float chamber of said carburetor and a fourth port communicating with said intake passage, and having a first passage intercommunicating said first and second ports, a second passage intercommunicating said second and fourth ports, and a third passage intercommunicating with third and fourth ports;
• a first valve element disposed in said housing and adapted to be operated by said operation shaft of said temperature detector, said first valve element being movably disposed to be opened and closed said first passage;
• a first spring means disposed in said housing and urging said first valve element in a closing direction;
• a second valve element disposed in said housing and adapted to be operated by said first valve element, said second valve element being movably disposed to be opened and closed said third passage;
• a second spring means disposed in said housing and urging said second valve element in a closing direction;
• a check valve disposed in said second passage, said check valve opening said second passage when a vacuum introduced from said fourth port is higher than the vacuum introduced from said second port and permitting transmission of the vacuum from said fourth port to said second port,
• whereby, when the temperature of said intake air is low, said first and second valve elements are moved to the closing positions so as to close said first and third passages, while, when the temperature of said intake air is raised, said first valve element is moved to the opening position to open said first passage so that air from atmosphere or other air source is supplied to said fourth port through said first port, whereas, when the temperature of said intake air is further increased, said second valve element is moved by said first valve element to the opening position to open said third passage and to allow the air from the atmosphere or other air source to flow said fourth port via said first port.