US3618578A

US3618578A - Motor vehicle fuel systems

Info

Publication number: US3618578A
Application number: US846776A
Authority: US
Inventors: Peter P Swatman; Peter G G Knight
Original assignee: British Motor Corp Ltd
Current assignee: British Motor Corp Ltd
Priority date: 1969-08-01
Filing date: 1969-08-01
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

System for preventing loss of vapors from a motor vehicle fuel system comprising a filter bed and connections to said bed from the carburetor float chamber and fuel tank, said filter being permanently vented through the air cleaner, and vented to the choke region of the carburetor whenever the engine is delivering more than a predetermined amount of power.

Description

United States Patent [72] Inventors PeterP.Swatman Olton, Solihull;

92 6 l 3 H1091 ll/ 33313 222 2 .lll3l 2 m Tml m Ha t. a e mam: e e l. .ul mm m m ie mn fpa .l TSLMK 38999 46666 99999 HHHHH 425600 28892 874 2 50470 17446 .A 23333 n m t m m v L 0 n C 0 0 w m n m n C h I h m n 0 m 7 a 99% Fu E 1Il 217 -1 3? ve flMMuoh P SANT 0. de mm i 8 i mmx AFPA llll 253 2247 [lll Primary Examiner-Laurence M. Goodridge Attorney-Holcombe, Wetherill & Brisebois Birlnlngham, England MOTOR VEHICLE FUEL SYSTEMS ABSTRACT: System for preventing loss of vapors from a motor vehicle fuel system comprising a filter bed and connec- 3 Claims, 1 Drawing Fig.

tions to said bed from the carburetor float chamber and fuel tank, said filter being permanently vented through the air cleaner, and vented to the choke region of the carburetor whenever the engine is delivering more than a predetermined a umw w 1 l 5 Mom-M2 u m H 2 0 l 2 l 0 mh c .I m I C mm IF m um uoooonooou (ooceooouno MOTOR VEHICLE FUEL SYSTEMS This invention relates to motor vehicle fuel systems of the kind in which a liquid-fuel tank, mounted on the vehicle, is arranged to supply fuel to the float chamber of a carburetor of the controllable jet, automatic variable-choke type having a fuel-metering jet controlled by a contoured metering needle in dependence upon the instantaneous position of a suctionoperated piston that controls the effective cross-sectional area of a choke in the main air passage of the carburetor.

The aim of the invention is to obviate, as far as possible, atmospheric pollution which is ordinarily caused by uncontrolled evaporative loss of fuel from a motor vehicle fuel system of the kind specified. To this end, according to the invention, the fuel tank and the carburetor float chamber are sealed to preclude uncontrolled evaporative loss of fuel, and the fuel vapor produced from them is trapped in a canister containing a bed of activated granular charcoal which adsorbs the fuel vapor; permanent communication is established between the usual engine air cleaner and the top of the canister; and from the base of the canister a connecting pipe leads to an outlet located in the carburetor body adjacent to the choke, this outlet being obturated by the suction-operated piston whenever the engine of the vehicle is operating under the smaller power output conditions of any legislatively imposed atmospheric pollution test cycle, but whenever the engine is operating at conditions requiring a greater power output, the outlet becomes uncovered by the piston with the result that purging of the canister then takes place by reason of the adsorbed fuel being entrained by the induced air flow and being discharged into the choke region of the carburetor.

The respective vapor spaces of the fuel tank and the carburetor float chamber are connected by piping to perforated rings which are disposed at the top of the charcoal bed inside the canister.

The above-mentioned outlet, for purging the canister, is located at such a height above the usual bridge member in the main air passage of the carburetor that it remains obturated by the smaller-diameter portion (i.e. the shank) of the suctionoperated piston until the flow of air through the main air passage is sufficiently great to cause the piston to be lifted to such an extent that the purge outlet becomes uncovered.

The accompanying drawing illustrates schematically a motor vehicle fuel system incorporating the invention. In this system a carburetor l of the controllable jet, automatic variable-choke type has a fuel-metering jet 2 controlled by a contoured metering needle 3 in dependence upon the instantaneous position of a suction-operated piston 4 which is located in a suction chamber 5. The piston 4 also controls the effective cross-sectional area of a choke 6 established, as usual, between the base of the piston and a bridge member 7 which contains the jet 2, the choke 6 being in the main air passage of the carburetor. Although this is not shown in the schematic drawing, a disc-type throttle valve is, as usual, located downstream of the jet 2.

When the carburetor l is in operation, the suction exerted in the substantially constant depression region (lying between the choke 6 and the throttle valve) causes the jet 2 to discharge liquid fuel drawn from a float chamber 8, by way of a pipe 9 and a jet assembly 10. The supply of liquid fuel to the float chamber 8, through a pipe 11 connected to a fuel tank 12. is controlled in the usual manner by a float needle 13.

What has so far been described with reference to the drawing pertains to the construction and operation of a well-known design of carburetor.

In accordance with the invention the fuel tank 12 and the carburetor float chamber 8 are sealed to preclude uncontrolled evaporative loss of fuel, and the fuel vapor produced from them is trapped in a canister 14 containing a bed of activated granular charcoal (not shown) which adsorbs the fuel vapor. To this end, the respective vapor spaces of the fuel tank 12 and the carburetor float chamber 8 are connected, by pipes 15 and 16 respectively, to corresponding perforated rings 15A and 16A disposed horizontally at the top of the charcoal bed.

By way of a pipe 17, permanent communication is established between the usual engine air cleaner (not shown) and the top of the charcoal canister 14.

From the base of the charcoal canister 14 a connecting pipe 18 leads to an outlet 19 located in the carburetor body adjacent to the choke 6. This outlet 19 is obturated by the shank of the suction-operated piston 4 whenever the engine of the vehicle is operating under the smaller power output conditions of any legislatively imposed atmospheric pollution test cycle (such as the so-called California cycle). But whenever the engine is operating at conditions requiring a greater power output, the outlet 19 becomes uncovered by the shank of the piston 4. Purging of the charcoal canister 14 then takes place by reason of the adsorbed fuel being entrained by the induced air flow and being discharged, from the outlet 19, into the choke region of the carburetor.

We claim:

1. A motor vehicle fuel system comprising a fuel tank and a carburetor having a float chamber and a suctionoperated piston which controls the area of the choke opening, both said fuel tank and said float chamber being sealed to preclude uncontrolled evaporative loss of fuel and connected through permanently open vent means to a canister containing a bed of material which adsorbs the fuel vapor; an air cleaner permanently connected to the top of the canister; and a connecting pipe leading from the base of said canister to an outlet so positioned in the carburetor body as to be obturated by said suction-operated piston whenever the engine of the vehicle is operating under the smaller output conditions of its operating range, but uncovered by said suction-operated piston whenever the engine is operating at conditions requiring a greater power output, whereby said canister is purged by suction of the fuel adsorbed therein through said connecting pipe and outlet into the choke region of the carburetor.

2. A system as claimed in claim 1 in which said bed of material is a bed of activated granular charcoal.

3. A motor vehicle fuel system according to claim 1, in which the respective vapor spaces of the fuel tank and the car buretor float chamber are connected by piping to perforated rings which are disposed at the top of the charcoal bed inside the canister.

Claims

1. A motor vehicle fuel system comprising a fuel tank and a carburetor having a float chamber and a suction-operated piston which controls the area of the choke opening, both said fuel tank and said float chamber being sealed to preclude uncontrolled evaporative loss of fuel and connected through permanently open vent means to a canister containing a bed of material which adsorbs the fuel vapor; an air cleaner permanently connected to the top of the canister; and a connecting pipe leading from the base of said canister to an outlet so positioned in the carburetor body as to be obturated by said suction-operated piston whenever the engine of the vehicle is operating under the smaller output conditions of its operating range, but uncovered by said suction-operated piston whenever the engine is operating at conditions requiring a greater power output, whereby said canister is purged by suction of the fuel adsorbed therein through said connecting pipe and outlet into the choke region of the carburetor.

3. A motor vehicle fuel system according to claim 1, in which the respective vapor spaces of the fuel tank and the carburetor float chamber are connected by piping to perforated rings which are disposed at the top of the charcoal bed inside the canister.