Carburettor for motor vehicle

Claim 2

In a carburetor for an internal combustion engine of a motor vehicle having a main mixture circuit adapted to supply an airfuel mixture to the carburetor induction passage for high-speed and acceleration operations of the engine, an idling and slowrunning mixture circuit adapted to supply a mixture to the carburetor induction passage for slow-running and deceleration operations of the engine, a throttle valve disposed in the carburetor induction passage for controlling the quantity and air-fuel ratio of the mixture supplied by the carburetor to the engine, and a fuel supply reservoir which supplies Fuel to the two circuits; a mixture supply control system comprising in combination an auxiliary fuel passage providing communication between said fuel reservoir and said main mixture circuit so as to supply additional fuel to said main mixture circuit, a suction-operated piston valve assembly for opening and closing said auxiliary fuel passage in response to the temperature of the engine, an auxiliary air passage providing communication between said suction-operated piston valve assembly and the carburetor induction passage downstream of said throttle valve for supplying additional air to the carburetor induction passage, and a bimetal device for controlling the opening and closing operations of said suction-operated piston valve assembly in response to the temperature of the engine for thereby supplying to the engine an appropriate amount of enriched mixture for the initial ''''coldengine'''' and subsequent warming-up operations, said suctionoperated piston valve assembly including two portions, one portion consisting of a housing mounted on the outside surface of the carburetor and defining a suction chamber, which housing has therein an axially movable piston and an air vent which is vented from the ambient air, said suction chamber communicating with said air passage through an orifice and with the fuel reservoir through a bore which has therein an axially movable piston rod connected to said first-mentioned axially movable piston and extending into said fuel reservoir and a compression spring biasing said piston rod toward said fuel reservoir, and the other portion consisting of a housing mounted in the body of the carburetor below the level in the liquid fuel contained in said fuel reservoir and defining a fuel chamber, which housing has therein an axially movable needle element in abutting engagement with said piston rod at their ends and a compression spring selected to be weaker in force than the first-mentioned compression spring and biasing said needle element in a direction opposite to that of the first-mentioned compression spring, said fuel chamber communicating with said fuel passage and with said fuel reservoir through a bore in the second-mentioned housing, said needle element having a radially extending tapered portion for shutting off the fuel flow through said second-mentioned bore, whereby with no vacuum present in said suction chamber said piston rod forces said needle element in a direction to open the second-mentioned bore, while with a vacuum present in said suction chamber said piston rod is urged due to he vacuum in a direction to close the second-mentioned bore, and said said bimetal device including a bimetal member mounted outside the first-mentioned housing of said piston valve assembly and carrying a conical member to be seated air-tightly on said air vent, said bimetal member being adapted to hold said conical member so as to open said air vent when the engine is cold and being adapted to bend toward said air vent so as to close said air vent as soon as the temperature of the engine exceeds a predetermined value.

Claim 3

In a carburetor for an internal combustion engine of a motor vehicle having a fuel supply reservoir, a carburetor induction passage, a throttle valve disposed in said carburetor induction passage, a main venturi and a small venturi, the combination comprising a main mixture circuit opening into said small venturi for supplying an air-fuel mixture to said carburetor induction passage for high-speed and acceleration operations of the engine, said main mixture circuit having a main fuel jet communicating with said fuel supply reservoir, a main fuel and air mixer communicating with said main fuel jet and a main nozzle opening into said small venturi, said main fuel and air mixer having formed at its bottom an orifice and its top an air bleed vented from the atmosphere, the effective cross-sectional areas of said orifice and said air bleed being so calibrated as to provide a desired amount of lean air-fuel mixture so that a leaN mixture is produced in said main mixture circuit for delivering to the engine, an idling and slow-running mixture circuit opening into said carburetor induction passage downstream of said main venturi for supplying an air-fuel mixture to said carburetor induction passage for low-speed and deceleration operations of the engine, said idling and slow-running mixture circuit having a slow-running port located at a position closely adjacent to the periphery of said throttle valve when it is substantially fully closed and an idling port located downstream of said throttle valve, said idling and slow-running mixture circuit having a slow-running fuel and air mixer which has formed at its bottom an orifice and a first air bleed vented from the ambient atmosphere and a second air bleed downstream of said first air bleed, the effective cross-sectional areas of said first and second air bleeds being so calibrated as to admit air from the ambient atmosphere at desired flow rates to provide the air-fuel mixture for the low-speed and deceleration operations of the engine, an auxiliary fuel passage providing communication between said fuel supply reservoir and said main mixture circuit so as to supply additional fuel to said main mixture circuit, a suction-operated piston valve assembly for opening and closing said auxiliary fuel passage in response to the temperature of the engine, an auxiliary air passage providing communication between said suction-operated piston valve assembly and said carburetor induction passage downstream of said throttle valve for supplying additional air to said carburetor induction passage, and a bimetallic device for controlling the opening and closing operations of said suction-operated piston valve assembly in response to the temperature of the engine for thereby supplying to the engine an appropriate amount of enriched air-fuel mixture for the initial ''''cold-engine'''' and subsequent warming-up operations, said suction-operated piston valve assembly including first and second portions, said first portion consisting of a housing mounted on the outside surface of the carburetor and having a suction chamber and an air vent from the ambient atmosphere, an axially movable suction-operated piston accommodated in said suction chamber, said suction chamber communicating with said auxiliary air passage through an orifice and with said fuel supply reservoir through a bore, an axially movable piston rod accommodated in said bore and connected to said suction-operated piston, said axially movable piston rod extending into said fuel supply reservoir, and a compression spring biasing said piston rod toward said fuel supply reservoir, and said second portion consisting of a housing mounted in the body of the carburetor below the level in the liquid fuel in said fuel supply reservoir, a fuel chamber defined in said second-mentioned housing and leading to said auxiliary fuel passage through a bore and communicating with said fuel supply reservoir, an axially movable needle element accommodated in said second-mentioned housing and in abutting engagement with said axially movable piston rod at their ends and a compression spring selected to be weaker in force than the first-mentioned compression spring and biasing said needle element in a direction opposite to that of the first-mentioned compression spring, said needle element having a radially extending tapered portion for shutting off the fuel flow through said second-mentioned bore, whereby with no vacuum present in said suction chamber said piston rod forces said needle element in a direction to open said second-mentioned bore, while with a vacuum present in said suction chamber said piston rod is urged due to the vacuum in a direction to close the second-mentioned bore, and said bimetal device including a bimetal member mounted outside the first-mentioned housing of said suction-operated piston valve assembly and carrying a conical member to be seated air-tightly on said air vent, said bimetal member being adapted to hold Said conical member so as to close said air vent when the engine is cold and being adapted to bend away from said air vent so as to open said air vent as soon as the temperature of the engine exceeds a predetermined value.

Claim 4

In a carburetor for an internal combustion engine of a motor vehicle having a fuel supply reservoir, a carburetor induction passage, a throttle valve disposed in said carburetor induction passage, a main venturi and a small venturi, the combination comprising a main mixture circuit opening into said small venturi for supplying an air-fuel mixture to said carburetor induction passage for high-speed and acceleration operations of the engine, said main mixture circuit having a main fuel jet communicating with said fuel supply reservoir, a main fuel and air mixer communicating with said main fuel jet and a main nozzle opening into said small venturi, said main fuel and air mixer having formed at its bottom an orifice and its top an air bleed vented from the atmosphere, the effective cross-sectional areas of said orifice and said air bleed being so calibrated as to provide a desired amount of lean air-fuel mixture so that a leaN mixture is produced in said main mixture circuit for delivering to the engine, an idling and slow-running mixture circuit opening into said carburetor induction passage downstream of said main venturi for supplying an air-fuel mixture to said carburetor induction passage for low-speed and deceleration operations of the engine, said idling and slow-running mixture circuit having a slow-running port located at a position closely adjacent to the periphery of said throttle valve when it is substantially fully closed and an idling port located downstream of said throttle valve, said idling and slow-running mixture circuit having a slow-running fuel and air mixer which has formed at its bottom an orifice and a first air bleed vented from the ambient atmosphere and a second air bleed downstream of said first air bleed, the effective cross-sectional areas of said first and second air bleeds being so calibrated as to admit air from the ambient atmosphere at desired flow rates to provide the air-fuel mixture for the low-speed and deceleration operations of the engine, an auxiliary fuel passage providing communication between said fuel supply reservoir and said main mixture circuit so as to supply additional fuel to said main mixture circuit, a suction-operated piston valve assembly for opening and closing said auxiliary fuel passage in response to the temperature of the engine, an auxiliary air passage providing communication between said suction-operated piston valve assembly and said carburetor induction passage downstream of said throttle valve for supplying additional air to said carburetor induction passage, and a bimetallic device for controlling the opening and closing operations of said suction-operated piston valve assembly in response to the temperature of the engine for thereby supplying to the engine an appropriate amount of enriched air-fuel mixture for the initial ''''cold-engine'''' and subsequent warming-up operations, said suction-operated piston valve assembly including first and second portions, said first portion consisting of a housing mounted on the outside surface of the carburetor and having a suction chamber and an air vent from the ambient atmosphere, an axially movable suction-operated piston accommodated in said suction chamber, said suction chamber communicating with said auxiliary air passage through an orifice and with said fuel supply reservoir through a bore, an axially movable piston rod accommodated in said bore and connected to said suction-operated piston, said axially movable piston rod extending into said fuel supply reservoir, and a compression spring biasing said piston rod toward said fuel supply reservoir, and said second portion consisting of a housing mounted in the body of the carburetor below the level in the liquid fuel in said fuel supply reservoir, a fuel chamber defined in said second-mentioned housing and leading to said auxiliary fuel passage through a bore and communicating with said fuel supply reservoir, an axially movable needle element accommodated in said second-mentioned housing and in abutting engagement with said axially movable piston rod at their ends and a compression spring selected to be weaker in force than the first-mentioned compression spring and biasing said needle element in a direction opposite to that of the first-mentioned compression spring, said needle element having a radially extending tapered portion for shutting off the fuel flow through said second-mentioned bore, whereby with no vacuum present in said suction chamber said piston rod forces said needle element in a direction to open said second-mentioned bore, while with a vacuum present in said suction chamber said piston rod is urged due to the vacuum in a direction to close the second-mentioned bore, and said bimetal device including a bimetal member mounted outside the first-mentioned housing of said suction-operated piston valve assembly and carrying a conical member to be seated air-tightly on said air vent, said bimetal member being adapted to hold Said conical member so as to close said air vent when the engine is cold and being adapted to bend away from said air vent so as to open said air vent as soon as the temperature of the engine exceeds a predetermined value.